pubs.acs.org/JACS                                                                                                                                Article
 
 
 
                                                                                                          In Situ Raman Spectroscopic Insight of Hydrogen Spillover in
                                                                                                          Electrocatalytic Hydrogenation
                                                                                                          Yan Liu, Ze-Yu Zhang, Jie Wei,* Yan Liu, Hua Zhang,* and Jian-Feng Li*
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                                                                                                          ABSTRACT: Given the crucial role of adsorbed hydrogen species (*H) in
   Downloaded via ZHEJIANG UNIV OF TECHNOLOGY on May 22, 2026 at 02:09:57 (UTC).
 
 
 
 
                                                                                                          electrochemical hydrogenation reactions, manipulating hydrogen spillover to
                                                                                                          facilitate the generation and migration of *H is highly necessary. However,
                                                                                                          the strong coupling between hydrogen activation sites and hydrogenation
                                                                                                          sites, together with the coexistence of protons and water molecules in
                                                                                                          practical electrocatalytic systems, renders a grand challenge for the in situ
                                                                                                          monitoring of hydrogen spillover. Herein, using single-atom Ru-doped Cu as
                                                                                                          a model catalyst, the spectroscopic visualization of hydrogen spillover under
                                                                                                          electrochemical conditions was realized by in situ surface-enhanced Raman
                                                                                                          spectroscopy. Taking para-nitrothiophenol as the probe molecule, we
                                                                                                          elucidated that the hydrogen spillover distance was facet-dependent, with
                                                                                                          Cu(111) being more active for electrocatalytic hydrogenation than Cu(100).
                                                                                                          Notably, electrochemical hydrogen spillover distances were tunable with the
                                                                                                          variation of applied potentials, which increased, ranging from 0.8 to 2.6 nm as the potentials shifted negatively. Moreover, by
                                                                                                          leveraging the hydrogen spillover effect to increase the hydrogen coverage on the Cu(111) surface, we found that the rate-
                                                                                                          determining step of nitrate electroreduction could be altered, resulting in a significant enhancement of catalytic performance.
 
 
                                                                                                          ■    INTRODUCTION
                                                                                                          The electrochemical hydrogenation (ECH) reaction, driven by
                                                                                                                                                                                          ideal model catalysts to gain more profound insight about the
                                                                                                                                                                                          hydrogen spillover mechanism in complex reaction net-
                                                                                                          renewable electricity using clean water as the hydrogen source,                 works.33,34 For instance, isolated Pd atoms on the Cu surface
                                                                                                          is emerging as an appealing approach to produce high-value-                     significantly lowered the energy barrier of H2 dissociation and
                                                                                                          added chemicals.1−6 Typically, the dissociation of H2O to form                  adsorption, allowing for reactive hydrogen to diffuse across the
                                                                                                          surface-adsorbed hydrogen species (*H) and the subsequent                       Cu surface and thus achieving highly selective hydrogenation
                                                                                                          consumption of *H are significantly essential for the ECH                       of styrene and acetylene.30 Similarly, highly diluted Pd single
                                                                                                          process.7−13 Therefore, the precise manipulation of hydrogen                    atoms on Cu supports demonstrated the facet-dependent
                                                                                                          spillover, which involves the transfer of H species from metal                  hydrogen spillover, where the hydrogen atoms spilled from Pd
                                                                                                          sites onto the catalyst support, is highly necessary to facilitate              were readily utilized for the semihydrogenation of alkynes.31
                                                                                                          the generation and migration of *H, thereby enhancing the                       Despite these advances, direct observation of hydrogen
                                                                                                          catalytic performance.14−22 However, in most traditional                        spillover under reaction conditions, which is crucial for
                                                                                                          supported metal catalysts, the complex metal−support inter-                     clarifying reaction mechanisms and guiding catalyst design,
                                                                                                          face and the extremely closed active sites for hydrogen                         remains a formidable challenge, particularly in electrocatalytic
                                                                                                          activation and hydrogenation render great challenge to                          systems.35−39 The interplay among protons (H+), water
                                                                                                          separately investigate the process of hydrogen generation,                      molecules, and adsorbed hydrogen species (H*) in electro-
                                                                                                          migration, and utilization.23,24 Such a lack of well-defined                    catalytic reactions makes it difficult to unambiguously
                                                                                                          structures with spatially separated active sites has severely                   distinguish the contribution of spilled hydrogen from other
                                                                                                          hindered the in-depth understanding and stoichiometric                          hydrogen sources.40−43 Therefore, the development of ultra-
                                                                                                          evaluation of the hydrogen spillover effect.25−27                               sensitive in situ characterization techniques applicable to
                                                                                                             In recent years, the emergence of single-atom catalysts
                                                                                                          (SACs), where the metal atoms are isolated and dispersed on
                                                                                                          supports, has provided new opportunities for probing the                        Received: January 6, 2026
                                                                                                          hydrogen spillover effect.28,29 Owing to the isolated nature of                 Revised: March 7, 2026
                                                                                                          noble metal atoms, SACs inherently separate the sites for                       Accepted: March 11, 2026
                                                                                                          hydrogen dissociation from those for hydrogenation, thereby                     Published: March 16, 2026
                                                                                                          achieving a structural “decoupling” of the spillover proc-
                                                                                                          ess.17,30−32 Consequently, SACs have been widely applied as
 
                                                                                                                                               © 2026 American Chemical Society                                                    https://doi.org/10.1021/jacs.6c00294
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Figure 1. SEM images of (a) Ru1/Cu(111) and (b) Ru1/Cu(100). HAADF-STEM and corresponding EDS mapping of (c) Ru1/Cu(111) and (d)
Ru1/Cu(100). Ru K-edge (e) XANES and (f) EXAFS spectra of Ru1/Cu(111) and Ru1/Cu(100). (g) CV curves of Ru1/Cu(111) and Ru1/
Cu(100) in 1 M KOH. (h) Pb UPD for Ru1/Cu(111) and Ru1/Cu(100). (i) In situ Cu K-edge XAFS for Ru-doped octahedral Cu2O.
 
aqueous environments is highly desired to acquire fundamental               constructing a Raman-enhanced coupled nanostructure
insight, including the migration distance and the molecular                 composed of SHINs and single-atom Ru-doped Cu with
mechanism of hydrogen spillover in electrocatalytic reac-
                                                                            specific facets (denoted as Ru1/Cu(111) and Ru1/Cu(100),
tions.44−50
   Shell-isolated nanoparticle-enhanced Raman spectroscopy                  respectively). Taking para-nitrothiophenol (pNTP) as the
(SHINERS), as a new generation of spectroscopy, possesses                   probe molecule, we observed that the electrocatalytic hydro-
extremely high sensitivity and wide universality for in situ                genation on Cu(111) was more favorable than on (100) facets,
monitoring of the catalytic reaction.51−53 In SHINERS, Au
nanoparticles with the Raman enhancement effect are encased                 spectroscopically evidencing that the hydrogen spillover
in ultrathin silica to form shell-isolated nanoparticles (SHINs),           distance on Cu surfaces was facet-dependent. Moreover,
simultaneously isolating the interference of the Au core.54−57              electrochemical hydrogen spillover distances were tunable
Moreover, SHINERS could easily eliminate the interference                   with the variation of applied potentials, which increased,
from the signal of bulk water since only species close to the
surface could be enhanced, making it particularly well-suited               ranging from 0.8 to 2.6 nm as the potentials shifted negatively.
for in situ study of electrocatalytic reactions in aqueous                  Furthermore, we found that leveraging the hydrogen spillover
solution.58,59 Thus, it is appealing to combine SHINERS and                 effect to enhance hydrogen coverage on Cu(111) could alter
site-isolated SACs to elucidate the underlying mechanism of
                                                                            the rate-determining step in nitrate (NO3−) electroreduction,
hydrogen spillover in electrocatalytic reactions.
   Herein, we realized the spectroscopic visualization of                   significantly improving the catalytic activity toward NH3
hydrogen spillover under electrochemical conditions by                      production.
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Figure 2. (a) Scheme of in situ SHINERS study on the hydrogenation of pNTP. (b) Distribution of the electromagnetic field simulated by the 3D-
FDTD method. (c) Cross-sectional SEM and (d) typical SEM images of Ru1/Cu(111) assembled with SHINs. (e) HAADF-STEM and
corresponding EDS mapping of Ru1/Cu(111) assembled with SHINs. In situ Raman spectra of hydrogenation of pNTP on (f) Ru1/Cu(111) and
(g) Cu(111). (h) Conversion of pNTP over Ru1/Cu(111) and Ru1/Cu(100).
 
■   RESULTS
Design of Ru1/Cu(111) and Ru1/Cu(100) Catalysts
                                                                            structure (XANES) of the two catalysts were located between
                                                                            Ru foil and RuO2, indicating the oxidation state of Ru species
                                                                            in the two catalysts (Figure 1e). Figure 1f depicts the Ru K-
Octahedral Cu2O with {111} facets and cubic Cu2O with                       edge extended X-ray absorption fine structure (EXAFS)
{100} facets were initially synthesized by a wet chemical                   spectra of Ru1/Cu(111) and Ru1/Cu(100). The peaks at
method (Figure S1).60,61 The introduction of Ru single atoms                1.53 Å were ascribed to Ru−O bonds, which were originated
was achieved by immersing Cu2O into a RuCl3 solution before                 from the inevitable oxidation of catalysts after exposure to the
an electroreduction process to reduce Cu2O into Cu                          air.62 Notably, the peaks at 2.21 Å of the two catalysts were
nanoparticles with well-defined shapes. As shown in Figure                  assigned to Ru−Cu bonds, which were distinct from that of Ru
1a,b, the scanning electron microscopy (SEM) images of Ru1/                 foil (2.39 Å). The absence of the Ru−Ru bond verified the
Cu(111) and Ru1/Cu(100) showed that the facets were well-                   atomic dispersion of Ru in the two catalysts. The fitting results
preserved after the galvanic process, with a slightly increased             and the wavelet transform (WT)-EXAFS analysis also
surface roughness. The uniform distribution of Ru was                       identified the presence of Ru−Cu coordination in Ru1/
demonstrated by high-angle annular dark-field scanning                      Cu(111) and Ru1/Cu(100) (Figures S3 and S4, and Table
transmission electron microscopy (HAADF-STEM) combined                      S1).
with energy-dispersive X-ray spectroscopy (EDS) mapping                        To acquire more facet features of the Ru1/Cu(111) and
(Figure 1c,d). As displayed in Figure S2, the X-ray diffraction             Ru1/Cu(100) catalysts, we investigated the electrochemical
(XRD) patterns of Ru1/Cu(111) and Ru1/Cu(100) matched                       adsorption of OH− and lead underpotential deposition (UPD),
well with the metallic Cu without the observation of residual               respectively. Figure 1g shows the cyclic voltammetry (CV)
Cu2O phase after the electroreduction. To verify the chemical               curves of the two catalysts in 1 M KOH. The peaks of OH−
state and coordination structure of Ru species, we conducted                adsorption appeared at ∼0.42 and ∼0.33 V vs reversible
Ru K-edge X-ray absorption fine structure (XAFS) measure-                   hydrogen electrode (RHE) for Ru1/Cu(111) and Ru1/
ments for Ru1/Cu(111) and Ru1/Cu(100). The energy                           Cu(100), respectively, demonstrating the facet-dependent
adsorption edge profiles in the X-ray absorption near edge                  OH− adsorption behavior.61 In addition, the reduction peaks
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Figure 3. (a) Hydrogen spillover distance over Ru1/Cu(111) and Ru1/Cu(100) at different applied potentials. The in situ Raman spectra of pNTP
hydrogenation over (b) Ru1/Cu(111) and (c) Ru1/Cu(100) at different site densities of Ru. (d) Conversion of pNTP and (e) hydrogen spillover
distance at different site densities of Ru. (f) Scheme of hydrogen spillover on the surface of Ru1/Cu(111) and Ru1/Cu(100).
 
of Pb UPD for Ru1/Cu(111) and Ru1/Cu(100) were observed                    the plasmonic nanogap between the SHINs and the underlying
at −0.034 and −0.055 V vs RHE, respectively, further implying              catalysts via the three-dimensional finite difference time
that Ru1/Cu(111) and Ru1/Cu(100) inherited the surface                     domain (3D-FDTD) method. The Raman signals of adsorbed
features of cubic and octahedral Cu, respectively.63 More                  species on the catalysts could be magnified by 106, enabling in
importantly, we carried out in situ Cu K-edge XAFS to probe                situ Raman investigation into the hydrogenation reaction. The
the dynamic structure revolution during the electroreduction               cross-sectional SEM images clearly illustrated the multilayer
of Ru-doped Cu2O (Figures 1h and S5 and S6). It is obvious                 structure of SHINs-assembled Ru1/Cu(111) and Ru1/Cu-
that Cu2O was gradually reduced to metallic Cu with the                    (100) nanocomposites (Figures 2c and S8). As shown in SEM
increased applied potentials. Specifically, at the applied                 images, HAADF-STEM images, and EDS mapping results, the
potential of −0.6 V vs RHE, the disappearance of the Cu−O                  monolayer SHINs were uniformly distributed on the surface of
bond demonstrated the complete reduction of the oxide, which               Ru1/Cu(111) and Ru1/Cu(100) (Figures 2d,2e and S9).
was consistent with the XRD result.                                        Compared with catalysts alone and the physical mixture of
In Situ SERS Study of the Facet-Dependent Hydrogenation                    catalysts and SHINs, the Raman signal of pNTP was
on Ru1/Cu(111) and Ru1/Cu(100)                                             significantly magnified on SHINs-assembled catalysts, enabling
The reduction of pNTP to para-aminothiophenol (pATP)                       the in situ Raman investigation into the hydrogenation process
generally serves as a probe reaction with the conversion of the            (Figure S10).
nitro group to an amino group once in contact with surface-                   To investigate the facet-dependent hydrogenation of pNTP,
adsorbed H, enabling molecular-level visualization of the                  we initially conducted in situ Raman measurements at different
hydrogen spillover process.45−47 The electrochemical hydro-                applied potentials. The Raman peaks at 1337 and 1571 cm−1
genation of pNTP to para-aminothiophenol (pATP) was                        were ascribed to the symmetric nitro stretching vibration and
employed as a model reaction to assess the facet-dependent                 the phenyl ring modes of pNTP, respectively (Figure 2f,g).64
hydrogenation on Ru1/Cu(111) and Ru1/Cu(100). Given the                    As the potentials shifted negatively, the Raman peaks at 1571
SHINERS as an ultrasensitive spectroscopy technique to                     cm−1 gradually shifted to 1594 cm−1, which was assigned to the
investigate the catalytic reactions, we fabricated SHINs on the            benzene ring mode of pATP, indicating that pNTP was
surface of the catalysts to monitor the hydrogenation process.             gradually hydrogenated to pATP. As displayed in Figures 2f
Figure 2a illustrates the schemes of the hydrogenation reaction            and S11a, the emergence of pATP for Ru1/Cu(111) and Ru1/
over Ru1/Cu(111) assembled with SHINs. Ru1/Cu(111) and                     Cu(100) was observed at the potential of −0.1 V vs RHE. In
Ru1/Cu(100) were initially deposited on the glass carbon                   comparison, the counterparts without Ru incorporation were
electrodes as the working electrode, respectively, followed by             denoted as Cu(111) and Cu(100), respectively (Figure S12).
immersion in the solution of pNTP to adsorb the pNTP.                      The signals of pATP for Cu(111) and Cu(100) appeared until
Then, a monolayer of SHINs was prepared on the surface of                  the potential shifted to as negative as −0.4 V vs RHE,
electrodes via a universal method (Figure S7). Figure 2b shows             demonstrating that bare Cu could hardly activate H2O at low
the distribution of the electromagnetic (EM) field generated in            potentials (Figures 2g and S11b). As such, the hydrogenation
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Figure 4. (a) Free energy diagram of the *H generation over Ru1/Cu(111) and Cu(111). (b) Free energy diagram of the *H generation over Ru1/
Cu(100) and Cu(100). Free energy diagram of the hydrogen spillover over (c) Ru1/Cu(111) and (d) Ru1/Cu(100). The yellow, purple, red, and
white spheres represent Cu, Ru, O, and H atoms, respectively. The asterisk represents an adsorption site.
 
of pNTP on Ru1/Cu(111) and Ru1/Cu(100) below the                           1.8 nm, much higher than that on Cu(100) (0.8 nm),
potential of −0.3 V vs RHE could be attributed to the spillover            highlighting the superior hydrogen migration capability of the
hydrogenation with *H species generated on Ru sites and then               Cu(111) facet. With the negative shift of potentials, the
spilled over Cu facets. Notably, the signal of pNTP on Ru1/                hydrogen spillover distance initially extended and then
Cu(111) completely disappeared at −0.6 V vs RHE, whereas                   remained stable at higher potentials. Notably, at the potential
residual pNTP was still observed on Ru1/Cu(100). The more                  of −0.3 V vs RHE, the H spillover distance on Cu(111) facet
favorable hydrogenation of pNTP over Ru1/Cu(111) than                      was estimated to be 2.4 nm, which was longer than that on
Ru1/Cu(100) implied the superior hydrogen spillover on Ru1/                Cu(100) facet (1.9 nm). Previous studies have shown that,
Cu(111). Figure 2h displays the conversion of pNTP                         under nonelectrochemical conditions, hydrogen can migrate
calculated by the integrated areas of the peaks at 1337 cm−1.              over hundreds of nanometers across the Cu(100) surface.31
Obviously, the conversion over Ru1/Cu(111) was higher than                 This discrepancy might be caused by the consumption of the
that over Ru1/Cu(100), especially under the low potentials                 surface-adsorbed hydrogen species by water molecules or
(−0.1 ∼ −0.3 V vs RHE), further revealing that the hydrogen                protons under electrochemical conditions. To verify the
spillover effect under electrocatalytic hydrogenation was more             reliability of the quantified hydrogen spillover distance, we
profound on the Cu(111) facet than the Cu(100) facet.                      further regulated the site density of Ru atoms to investigate the
   To further clarify the facet effect on hydrogen spillover, we           conversion of pNTP (Table S2). When the spillover distance
conducted a series of control experiments. As shown in Figure              was smaller than half of the average distance between adjacent
S13, the coverage of adsorbed pNTP on the catalyst’s surface               Ru atoms, the pNTP conversion would increase with the
had no significant impact on the hydrogenation process.                    growing Ru site density until approaching 100%. As shown in
Besides, the plasmon-induced hot electrons are not sufficient              Figure 3b,3c, in situ Raman spectra of the hydrogenation
for driving the conversion of pNTP to pATP due to the fast                 process on Ru1/Cu(111) and Ru1/Cu(100) with different ns
charge-carrier recombination, implying that the hydrogenation              values were collected at −0.3 V vs RHE after 30 min reaction.
of pNTP originated from an electrochemical process (Figure                 As expected, the Raman peak associated with the −NO2 group
S14). Then, we estimated the spillover distance over different             of pNTP gradually decreased with increasing ns values for the
Cu facets based on the conversion of pNTP and the site                     two catalysts. Notably, Ru1/Cu(111) exhibited a higher pNTP
density of Ru atoms (ns, Ru atoms per 100 nm2). As displayed               conversion than Ru1/Cu(100) when ns was below 33,
in Figure 3a, at a low potential of −0.1 V vs RHE, the                     suggesting a broader hydrogenation range on the Cu(111)
hydrogen spillover distance on Cu(111) was measured to be                  surface (Figure 3d). Based on the conversion and the
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Figure 5. (a) Current density of Ru1/Cu(111) and Cu(111) in 0.5 M Na2SO4 containing 0.1 M KNO3. (b) Yield rate of NH3 on Ru1/Cu(111)
and Cu(111). (c) Scheme of hydrogen spillover for NO3− electroreduction. (d) EPR spectra of electrocatalysts under different conditions. The
DEMS results of (e) Ru1/Cu(111) and (f) Cu(111). (g) Free energy diagram of the NO3− reduction. The yellow, blue, red, and white spheres
represent Cu, N, O, and H atoms, respectively. The asterisk represents an adsorption site.
 
corresponding ns value, the hydrogen spillover distance for                Density Functional Theory (DFT) Calculations
Ru1/Cu(111) was estimated to be 2.0−2.4 nm, which is larger                DFT calculations were conducted to acquire deeper insight
than that for Ru1/Cu(100) (1.6−1.8 nm) (Figure 3e). In
                                                                           into the facet-dependent H spillover. As displayed in Figure
addition, the two catalysts with a sufficient surface Ru site
density to supply abundant *H both exhibited a fast kinetic of             4a,b, in terms of the barrier for H2O dissociation, the Ru sites
pNTP hydrogenation (Figure S15). In this regard, the facet-                on Ru1/Cu(111) and Ru1/Cu(100) were more active in
dependent hydrogenation of pNTP observed at lower Ru                       generating *H than the Cu sites on Cu(111) and Cu(100). In
densities was primarily governed by the hydrogen spillover                 this case, the doping of Ru would accelerate the generation of
distance. These results demonstrated that the Cu(111) facet                *H. We further calculated the free energy of hydrogen spillover
facilitated hydrogen spillover more than Cu(100).31                        over Ru1/Cu(111) and Ru1/Cu(100) to evaluate the spill
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ability of *H, respectively (Figure 4c,d). It is worth noting that           mediates (Figures S20 and S21). In addition, the energy barrier
the kinetic barrier for *H spillover on Ru1/Cu(111) was 0.59                 of PDS (*NH3 → * + NH3) in the *H-mediated pathway was
eV (Figure 4c), which was much lower than that on Ru1/                       0.30 eV, which was lower than that in the PCET pathway,
Cu(100) (Figures 4d and S16). As such, the abundant Cu                       manifesting the superiority of the *H-mediated pathway in the
hollow sites on Ru1/Cu(111) supported the migration of *H                    electroreduction of NO3−. As such, under the effect of *H
from the Ru sites, which was conducive to the hydrogenation                  spillover, the rate-determining step of nitrate electroreduction
of pNTP.                                                                     was altered, giving rise to a significant enhancement of catalytic
Catalytic Performance toward NO3− Electroreduction                           performance.
To further elucidate the hydrogen spillover effect on the
electrocatalytic reaction, we investigated the catalytic perform-
                                                                             ■    CONCLUSION
                                                                             In summary, we revealed the facet-dependent and potential-
ance of Ru1/Cu(111) and Cu(111) toward nitrate electro-
                                                                             dependent hydrogen spillover during the electrochemical
reduction, which is a promising pathway for renewable
                                                                             hydrogenation process using the SHINERS. As the potentials
ammonia production. As shown in Figure 5a, the current
                                                                             shifted negatively, the electrochemical hydrogen spillover
densities of Ru1/Cu(111) in the electrolyte containing 1 M
                                                                             distances increased, ranging from 0.8 to 2.6 nm for Cu(111)
KNO3 were much larger than those of Cu(111), implying the                    and (100) facets. In addition, we found that leveraging the
superior activity of Ru1/Cu(111). Then, we evaluated the                     hydrogen spillover effect to increase the hydrogen coverage on
performance of Ru1/Cu(111) with different site densities of                  the Cu(111) surface could alter the rate-determining step of
Ru. The production of NH3 in the electrolyte was quantified                  nitrate electroreduction, resulting in a significant enhancement
by the indophenol blue method (Figure S17). As displayed in                  of catalytic performance. This work provides a profound
Figure 5b, compared with Cu(111), the samples modified by                    understanding of hydrogen spillover under electrochemical
Ru all exhibited a higher yield rate of NH3. Notably, as the ns              conditions and guides the rational design of electrocatalysts
of Ru increased, the yield rate of NH3 initially increased but               with the hydrogen spillover concept.
then decreased. This phenomenon indicated that the moderate
Ru content could supply appropriate *H to match the
hydrogenation of nitrate, whereas excessive Ru would provide
superfluous *H to bind together, generating undesired H2
                                                                             ■      ASSOCIATED CONTENT
                                                                             * Supporting Information

 
(Figures 5c and S18). Given the crucial role of *H in the NO3−               The Supporting Information is available free of charge at
electroreduction, we conducted electron paramagnetic reso-                   https://pubs.acs.org/doi/10.1021/jacs.6c00294.
nance (EPR) measurements to probe the generation of *H                                Experimental procedures, characterization of pristine
using 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a *H                                 Cu2O, XRD of Ru1/Cu(111) and Ru1/Cu(100), EXAFS
trapping reagent. As displayed in Figure 5d, at the potential of                      fitting results, SEM and TEM of SHINs-assembled Ru1/
−0.3 V vs RHE, Ru1/Cu(111) showed stronger DMPO-H                                     Cu(100), in situ Raman of pNTP hydrogenation on
signals in the electrolyte without NO3− relative to Cu(111),                          SHINs-assembled Ru1/Cu(100), concentration−absorb-
demonstrating that the introduction of Ru promoted the H2O                            ance curve of NH4+, and the structure models of
dissociation to produce abundant *H.32 After the addition of                          intermediates for Cu(111) (PDF)
NO3−, the DMPO-H signals of Ru1/Cu(111) were undetect-
able, revealing that the generated *H was rapidly consumed to
boost the hydrogenation of NO3−.
   To understand the reaction pathways of NO3− electro-
                                                                             ■      AUTHOR INFORMATION
                                                                             Corresponding Authors
reduction, we performed electrochemical online differential                        Jie Wei − College of Energy, College of Materials, State Key
electrochemical mass spectrometry (DEMS) for Ru1/Cu(111)                              Laboratory of Physical Chemistry of Solid Surfaces, College of
and Cu(111). The signal of the *NO2 intermediate was not                              Chemistry and Chemical Engineering, School of Life Sciences,
detected for the two samples, implying the effective conversion                       College of Physical Science and Technology, Discipline of
of NO2− during the reaction process (Figure 5e,f). It is worth                        Intelligent Instrument and Equipment, iChEM, Fujian Key
noting that the signal of *NH2OH was observed only in                                 Laboratory of Advanced Materials, Xiamen University,
Cu(111), verifying that the NO3− electroreduction for                                 Xiamen 361005, China; Innovation Laboratory for Sciences
Cu(111) experienced the pathway containing *NH2OH                                     and Technologies of Energy Materials of Fujian Province
intermediates. In the case of Ru1/Cu(111), the absence of                             (IKKEM), Xiamen 361102, China; orcid.org/0009-
the *NH2OH signal indicated that Ru1/Cu(111) circumvented                             0003-5437-6345; Email: weij@xmu.edu.cn
the NH2OH pathway due to the sufficient supply of *H. To                           Hua Zhang − College of Energy, College of Materials, State
get a theoretical insight into the role of *H in NO3−                                 Key Laboratory of Physical Chemistry of Solid Surfaces,
electroreduction, we conducted DFT calculations based on                              College of Chemistry and Chemical Engineering, School of
the typical proton-coupled electron transfer (PCET) pathway                           Life Sciences, College of Physical Science and Technology,
and *H-mediated pathway for Cu(111), respectively. As                                 Discipline of Intelligent Instrument and Equipment, iChEM,
displayed in Figures 5g and S19, the step from *NO to                                 Fujian Key Laboratory of Advanced Materials, Xiamen
*NOH with an energy barrier of 0.36 eV served as the                                  University, Xiamen 361005, China; Innovation Laboratory
potential-determining step (PDS) in the PCET pathway,                                 for Sciences and Technologies of Energy Materials of Fujian
indicating the unfavorable generation of NH3. Surprisingly, in                        Province (IKKEM), Xiamen 361102, China; orcid.org/
the *H-mediated pathway, the *NO intermediate sponta-                                 0000-0001-9588-9030; Email: zhanghua@xmu.edu.cn
neously transformed into *NH with a quite negative free                            Jian-Feng Li − College of Energy, College of Materials, State
energy change (−1.58 eV), which was attributed to the                                 Key Laboratory of Physical Chemistry of Solid Surfaces,
spontaneous binding of *H with nitrogen-containing inter-                             College of Chemistry and Chemical Engineering, School of
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     Life Sciences, College of Physical Science and Technology,                    (4) Li, M.; Wu, Y.; Zhao, B.-H.; Cheng, C.; Zhao, J.; Liu, C.; Zhang,
     Discipline of Intelligent Instrument and Equipment, iChEM,                   B. Electrosynthesis of amino acids from NO and α-keto acids using
     Fujian Key Laboratory of Advanced Materials, Xiamen                          two decoupled flow reactors. Nat. Catal. 2023, 6, 906−915.
     University, Xiamen 361005, China; Innovation Laboratory                       (5) Xiong, H. C.; Yu, P. P.; Chen, K. D.; Lu, S. K.; Hu, Q. K.;
                                                                                  Cheng, T.; Xu, B. J.; Lu, Q. Urea synthesis via electrocatalytic
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     Province (IKKEM), Xiamen 361102, China; College of                           795.
     Chemistry, Chemical Engineering and Environment, Minnan                       (6) Kang, H.; Zhu, L.; Li, S. Y.; Yu, S. W.; Niu, Y. M.; Zhang, B. S.;
     Normal University, Zhangzhou 363000, China;                                  Chu, W.; Liu, X. C.; Perathoner, S.; Centi, G.; Liu, Y. F. Generation of
       orcid.org/0000-0003-1598-6856; Email: Li@                                  oxide surface patches promoting H-spillover in Ru/(TiOx)MnO
     xmu.edu.cn                                                                   catalysts enables CO2 reduction to CO. Nat. Catal. 2023, 6, 1062−
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Authors                                                                            (7) Tan, Q.; Li, L.; Li, Y.; Jiang, Z.; Ma, Y.; Qu, Y.; Li, J. Tandem
  Yan Liu − College of Energy, College of Materials, State Key                    electrocatalytic alkyne semihydrogenation over bicomponent catalysts
    Laboratory of Physical Chemistry of Solid Surfaces, College of                through hydrogen spillover. Angew. Chem., Int. Ed. 2024, 63,
    Chemistry and Chemical Engineering, School of Life Sciences,                  No. e202400483.
                                                                                   (8) Cheng, C.; Chen, F.; Zhang, B.; Zhao, B. H.; Du, X. Promoting
    College of Physical Science and Technology, Discipline of                     water dissociation and weakening active hydrogen adsorption to boost
    Intelligent Instrument and Equipment, iChEM, Fujian Key                       the hydrogen transfer reaction over a Cu-Ag superlattice electro-
    Laboratory of Advanced Materials, Xiamen University,                          catalyst. Angew. Chem., Int. Ed. 2025, 64, No. e202413897.
    Xiamen 361005, China                                                           (9) Fu, H. Q.; Zhou, M.; Liu, P. F.; Liu, P.; Yin, H.; Sun, K. Z.; Yang,
  Ze-Yu Zhang − College of Energy, College of Materials, State                    H. G.; Al-Mamun, M.; Hu, P.; Wang, H. F.; Zhao, H. Hydrogen
    Key Laboratory of Physical Chemistry of Solid Surfaces,                       spillover-bridged Volmer/Tafel processes enabling ampere-level
    College of Chemistry and Chemical Engineering, School of                      current density alkaline hydrogen evolution reaction under low
    Life Sciences, College of Physical Science and Technology,                    overpotential. J. Am. Chem. Soc. 2022, 144, 6028−6039.
    Discipline of Intelligent Instrument and Equipment, iChEM,                     (10) Li, J.; Hu, J.; Zhang, M.; Gou, W.; Zhang, S.; Chen, Z.; Qu, Y.;
    Fujian Key Laboratory of Advanced Materials, Xiamen                           Ma, Y. A fundamental viewpoint on the hydrogen spillover
    University, Xiamen 361005, China                                              phenomenon of electrocatalytic hydrogen evolution. Nat. Commun.
                                                                                  2021, 12, No. 3502.
  Yan Liu − School of Chemistry and Materials Science, Anhui                       (11) Fan, H.; Yang, Q. Q.; Fang, S. R.; Xu, Y. N.; Lv, Y.; Lin, H. Y.;
    Normal University, Wuhu 241000, China                                         Lin, M. Y.; Liu, J. K.; Wu, Y. X.; Yuan, H. Y.; Dai, S.; Liu, P. F.; Yang,
Complete contact information is available at:                                     H. G. Operando stable palladium hydride nanoclusters anchored on
https://pubs.acs.org/10.1021/jacs.6c00294                                         tungsten carbides mediate reverse hydrogen spillover for hydrogen
                                                                                  evolution. Angew. Chem., Int. Ed. 2024, 63, No. e202412080.
Notes                                                                              (12) Bao, D.; Huang, L.; Gao, Y.; Davey, K.; Zheng, Y.; Qiao, S. Z.
                                                                                  Dynamic creation of a local acid-like environment for hydrogen
The authors declare no competing financial interest.                              evolution reaction in natural seawater. J. Am. Chem. Soc. 2024, 146,
 
■   ACKNOWLEDGMENTS
This work was supported by NSFC (52571257, 22302184,
                                                                                  34711−34719.
                                                                                   (13) Chen, J.; Chen, C.; Qin, M.; Li, B.; Lin, B.; Mao, Q.; Yang, H.;
                                                                                  Liu, B.; Wang, Y. Reversible hydrogen spillover in Ru-WO3‑x enhances
                                                                                  hydrogen evolution activity in neutral pH water splitting. Nat.
22361132532, 22525042, T2293692, U25A20558 and                                    Commun. 2022, 13, No. 5382.
22539001), the Industry-University-Research Joint Innovation                       (14) Conner, W. C.; Falconer, J. L. Spillover in heterogeneous
Project of Fujian Province, China (2024H6023), the Natural                        catalysis. Chem. Rev. 1995, 95, 759−788.
Science Foundation of Fujian Province (2025J011007), the                           (15) Prins, R. Hydrogen spillover. Facts and fiction. Chem. Rev.
Fundamental Research Funds for the Central Universities                           2012, 112, 2714−2738.
(20720250086 and 20720250119), the Fundamental and                                 (16) Zaera, F. The long and winding road to catalysis. Nature 2017,
Interdisciplinary Disciplines Breakthrough Plan of the Ministry                   541, 37−38.
of Education of China (JYB2025XDXM201), and the State                              (17) Marcinkowski, M. D.; Jewell, A. D.; Stamatakis, M.; Boucher,
Key Laboratory of Fine Chemicals, Dalian University of                            M. B.; Lewis, E. A.; Murphy, C. J.; Kyriakou, G.; Sykes, E. C. H.
                                                                                  Controlling a spillover pathway with the molecular cork effect. Nat.
Technology (KF 2401).
                                                                                  Mater. 2013, 12, 523−528.
 
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