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http://pubs.acs.org/journal/aelccp Letter Ternary Facet Junction Engineered Cu O Photocathode for Efficient 2 Urea Synthesis via CO and NO − Co-reduction 2 3 Hong Liang, Min Li,* Zhiheng Li, Xiaowen Liu, Xinhao Xu, Shixin Yu, Wenfu Xie, Tianyu Zhang,* Haohong Duan,* and Qiang Wang* CiteThis:ACSEnergyLett.2026,11,3853−3860 ReadOnline ACCESS * Metrics&More ArticleRecommendations sı SupportingInformation ABSTRACT: Facet junction engineering offers an effective strategy to manipulate charge separation in photoelectrocatalysis (PEC), yet its role in CO and NO − co-reduction toward urea 2 3 synthesis remains unexplored. Herein, ternary facet junction polyhedral Cu O photocathodes exposing {100}, {110}, and 2 {111} facets were synthesized via a pH-controlled precipitation strategy. Density functional theory (DFT) calculations and selective photodeposition experiments reveal that the coexistence of anisotropic facets generates internal electric fields across the junctions, enabling directional charge carrier migration and suppressing charge recombination. Consequently, ternary facet Cu O delivers markedly enhanced PEC urea synthesis perform- 2 ancecomparedwiththoseofsingleandbinaryfacetjunctionsamples.Insituinfraredspectroscopyandcontrolexperimentsidentify key C−N coupling intermediates, elucidating the mechanism by which facet junction regulated charge dynamics promote CO / 2 NO −co-reduction.ThisworkuncoversapreviouslyunrecognizedfunctionoffacetjunctionsinPECureasynthesisandprovidesa 3 general design strategy for efficient photocathodes toward sustainable carbon−nitrogen conversion. The simultaneous conversion of CO and nitrogen- carrierdynamics.16Theanisotropicbandstructureandsurface 2 containing pollutants like nitrate (NO −) into value- states between different crystal facets can induce directional 3 added chemicals has emerged as a promising strategy for migrationofchargecarriers,formingfacethomojunctionsthat achieving carbon neutrality and resource circularity.1,2 Among promotechargeseparation.17,18Forinstance,the{001}/{101} various target products, urea is a key nitrogen fertilizer and binary facet junction in TiO promotes the migration of 2 industrial chemical that plays a critical role in global food photogenerated electrons and holes, enhancing photocatalytic security.3,4 However, industrial urea synthesis primarily relies CO reduction.19 Except binary surface heterojunctions, our 2 on the energy-intensive Haber−Bosch and urea-carbonation previous workalso demonstrated that18-faceted BiOClsingle processes,whichoperateunderharshconditions(150−200°C crystals with a {001}/{102}/{112} ternary junction signifi- and150−200bar)andgeneratesubstantialcarbonemissions.5 cantly enhanced photoredox activity.20 However, the applica- Developing a sustainable and mild route for urea synthesized tionofternaryfacetjunctionsinPECco-reductionofCO and from CO 2 and NO 3 − therefore remains an urgent challenge. NO 3 − remains largely unexplored. 2 Electrocatalyticco-reductionofCO 2 andnitratehasrecently Cu 2 O is a p-type semiconductor with strong visible light emerged as a feasible approach toward green urea synthesis absorption, suitable band positions, and intrinsic catalytic under ambient conditions.6−8 Despite notable progress, this activity toward CO activation, making it an attractive 2 strategy typically requires large external bias and suffers from photocathode material.21,22 Cu-based sites are known to limited energy efficiency.9,10 Photoelectrocatalysis, which facilitate CO activation and C−N coupling.23,24 Recent 2 synergistically couples solar energy with a small applied bias, studies have demonstrated that rationally designed Cu-based offers significant advantages.11−13 Integrating photoelectrodes catalysts, such as introducing single-atom catalysts and Cu- withasmallappliedpotentialoffersacompellingalternativeby enabling efficient charge separation, accelerating interfacial kinetics,andreducingoverallenergyinput.14Nevertheless,the Received: January16,2026 Revised: March26,2026 performance of PEC systems is still constrained by sluggish Accepted: March30,2026 interfacial reaction kinetics and inefficient charge separation within photoelectrodes.15 Published: April 7,2026 Facet engineering has attracted growing interest as an effective strategy to tailor surface electronic structure and ©2026AmericanChemicalSociety https://doi.org/10.1021/acsenergylett.6c00152 3853 ACSEnergyLett.2026,11,3853−3860 .)CTU( 05:50:30 ta 6202 ,51 yaM no YGOLONHCET FO VINU GNAIJEHZ aiv dedaolnwoD .selcitra dehsilbup erahs yletamitigel ot woh no snoitpo rof senilediuggnirahs/gro.sca.sbup//:sptth eeS
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ACS Energy Letters http://pubs.acs.org/journal/aelccp Letter Figure1.(a)SEMimagesandcorrespondinggeometricaldiagramsoffivedifferentCuOcatalysts;TEMimagesof(b)CuO-cand(c)CuO-o; 2 2 2 (d)XRDspectra of the CuOcatalystswithdifferent morphologiesandcrystal structures. 2 containingbimetallicsystems,caneffectivelystabilize*COand and directional carrier migration, leading to markedly *NO intermediates, lower C−N coupling barriers, and enhanced PEC urea synthesis from CO and NO −. 2 2 3 thereby enhance urea synthesis performance.25 For example, Furthermore, in situ FTIR reveals the formation of *OCO, confined Cu single atom sites within an atomically precise *CO, and *OCNO intermediates, confirming that the ternary Ti O Bz cluster have been reported to form a hydrophilic facet junction facilitates efficient C−N coupling between the 16 24 24 cavity−hydrophobic shell structure, enhancing intermediate CO and NO − derived species. This work not only offers a 2 3 confinement and enabling efficient PEC urea synthesis from strategyfordesigningefficientphotocathodematerialsviafacet CO andnitrate.26Inaddition,asymmetricamorphousCu−Zn engineering to enhance photogenerated charge separation but 2 atomic assemblies with reversed oxidation states spatially also opens up a novel pathway for urea synthesis through the decoupleNO −andCO activation,selectivelypromotingNO co-utilization of carbon and nitrogen resources. 2 2 formation and lowering the C−N coupling barrier, thereby Polyhedral Cu O crystals with different facets were 2 achieving high PEC urea synthesis performance.27 synthesized using a room-temperature precipitation method ThishighlightsthecriticalroleofCusitesinpromotingthe bytuninghydroxideionconcentrationduringsynthesis(0.6to selective C−N bond formation. In our previous work, Cu O 6.8 M). Scanning electron microscopy (SEM) images clearly 2 was demonstrated to enable urea formation via PEC co- revealuniformCu Oparticleswithanaveragesizeof1−2μm 2 reduction of CO and NO −.13 However, conventional single- (Figure 1a). In the absence of OH−, Cu O exhibits a well- 2 3 2 facet Cu O photocathodes suffer from inefficient charge defined cubic morphology, exposing only a single facet. With 2 separation, which limits the utilization of photogenerated increasing OH− concentration, new facets gradually emerge at electrons and ultimately constrains urea synthesis efficiency. the cube edges and vertices, which continuously expand and Notably, owing to facet-dependent electronic structures, ultimatelydriveacompletemorphologicaltransformationfrom surface charge distributions, and active sites, Cu O provides cubestooctahedra.Accordingly,theCu Osampleswithcubic, 2 2 an ideal platform for facet engineering, offering a promising edge-truncated cubic, edge and corner truncated octahedral, strategy to overcome the intrinsic charge separation truncated octahedral, and fully octahedral morphologies were limitations.28 named Cu O-c, Cu O-etc, Cu O-ecto, Cu O-to, and Cu O-o, 2 2 2 2 2 Herein, wereporta ternaryfacetjunctionengineered Cu O respectively.High-resolutiontransmissionelectronmicroscopy 2 photocathode by precisely tuning hydroxide concentration (HR-TEM) analysis confirms that Cu O-c and Cu O-o 2 2 during synthesis to simultaneously expose {100}, {110}, and predominantly expose {100} and {111} facets (Figures 1b, {111} facets. The resulting polyhedral Cu O establishes S1 and S2), respectively. According to crystallographic 2 cascade band alignments that enable spatial charge separation principles, the truncation planes emerging at the cube edges 3854 https://doi.org/10.1021/acsenergylett.6c00152 ACSEnergyLett.2026,11,3853−3860
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ACS Energy Letters http://pubs.acs.org/journal/aelccp Letter Figure2.(a)UV−visandTaucplot(illustration)forCuO-c,CuO-ecto,andCuO-o;(b)UPSvaluebandofCuO-c,CuO-ecto,andCuO-o; 2 2 2 2 2 2 (c)schematicbandstructuresofCuO-c,CuO-ecto,andCuO-o;DFTforbandstructureof(d)CuO(100),(e)CuO(110),and(f)CuO 2 2 2 2 2 2 (111)crystalfacets;(g)schematicdiagramofelectrontransferontheCuO-ectosurface;SEMimagesofMnO depositedonCuO-c(h)andPt 2 x 2 depositedonCuO-o (i)and CuO-ecto(j). 2 2 correspond to {110} facets. Consequently, Cu O-etc exposes the most positive valence band among the samples, high- 2 {100}/{110} facets, Cu O-to exposes {100}/{111} facets, lightingthestrongfacet-dependenceoftheelectronicstructure 2 whereas Cu O-ecto simultaneously exposes {100}, {110}, and (Figure 2c). 2 {111} facets. X-ray diffraction (XRD) (Figure 1d), X-ray To elucidate the band positions of individual crystal facets photoelectron spectroscopy (XPS) (Figure S3), and Auger and provide a basis for analyzing carrier migration across the electronspectroscopy(AES)(FigureS4)analysesconfirmthe facet junctions, DFT calculations were performed for the phase purity, high crystallinity, and surface chemical {100}, {110}, and {111} facets (Figure 2d−f). The results composition of all samples. Notably, the diffraction peaks of showthattheCBpositionofthe{110}facetismorenegative Cu O-ecto exhibit a slight overall shift in 2θ (∼0.05°). The 2 than that of the {100} facet, which, in turn, is more negative morphology-dependent angular shift is consistent with trends than that of the {111} facet. In contrast, the valence band reported in the relevant literature.29,30 exhibitsadifferenttrend;the{111}facethasthemostpositive To further confirm the facet junction in Cu O and explore 2 valence band position, followed by the (110) facet and the the charge separation and migration behavior of catalysts, the {100} facet. Consequently, the {100}/{110} binary facet band structures of different Cu O samples were first 2 junction and {111}/{100} binary facet junction can form in investigated.31 UV−vis diffuse reflectance spectra (DRS) Cu O-etcandCu O-to,whileCu O-etcouniquelyconstructsa show that all Cu O catalysts exhibit strong visible light 2 2 2 2 {100}/{110}/{111}ternaryfacetjunction(Figure2g).Inthis absorption between 450 and 700 nm (Figures 2a and S5). As ternary facet junction, electrons migrate from the {110} facet the Cu O morphology evolves from a cube to an octahedron, 2 to the {100} facet and subsequently to the {111} facet, theabsorptionedgeexhibitsanoticeableblueshift,indicatinga whereas holes migrate from the {110} and {111} facet to the slightincreaseinbandgapenergy.Taucanalysisfurtherreveals {100}facet,enablingefficientspatialseparationanddirectional that the bandgap energies (E) of Cu O-c, Cu O-ecto, and g 2 2 Cu O-o are 1.88, 1.94, and 1.92 eV, respectively. Mott− transport of charge carriers. Such charge transfer behavior is 2 Schottky analysis shows p-type semiconductor characteristics consistent with previous reports on facet junction behav- forallsamples,withflatbandpotentialsof−0.15V(Cu 2 O-c), ior.32−34 Additionally, the work functions of Cu 2 O with −0.03 V (Cu 2 O-o), and 0.07 V (Cu 2 O-ecto) vs Ag/AgCl different morphologies follow the order Cu 2 O-o (3.39 eV) > (FiguresS6andS7).Combinedwithultravioletphotoelectron Cu 2 O-c (3.34 eV) > Cu 2 O-ecto (3.19 eV) (Figure S8). When spectroscopy(UPS)(Figure2b)andMott−Schottkymeasure- Cu O-c comes into contact with Cu O-o, electrons transfer 2 2 ments,thebandedgepositionsweredetermined,showingthat from the lower work function {100} facetsto the higher work Cu O-ecto possesses the most negative conduction band and function{111}facetsuntilFermilevelequilibriumisachieved, 2 3855 https://doi.org/10.1021/acsenergylett.6c00152 ACSEnergyLett.2026,11,3853−3860
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ACS Energy Letters http://pubs.acs.org/journal/aelccp Letter Figure3.(a)SurfacechargeseparationefficiencyoftheCuO-ectocatalyst;(b)theapparentcarrierdensitiesand(c)theappliedbiasphoton-to- 2 currentefficiencyforureasynthesisofCuO-c,CuO-ecto,andCuO-o.(d)Correspondingtime-resolvedphotoluminescencedecaycurvesunder 2 2 2 300nm excitation. further confirming the existence of directional electron indicatesthatnearlyhalfofthephotogeneratedchargecarriers migration. can effectively participate in interfacial reactions, highlighting Selective photodeposition of Pt and MnO was carried out the favorable surface charge transfer capability of the catalyst. x using H PtCl and MnCl as precursors to experimentally Moreover, further calculations reveal that Cu O-ecto exhibits 2 6 2 2 validate the proposed charge migration pathways. Under thehighestapparentcarrierdensity,reaching4.29×1021cm−3 illumination, photogenerated electrons reduce Pt4+ to Pt (Figures3bandS13).Additionally,theappliedbiasphoton-to- nanoparticles, while photogenerated holes oxidize Mn2+ to current efficiency (ABPE) for urea synthesis further confirms MnO.17,35,36 MnO uniformly deposits on the {100} facet of that Cu O-ecto delivers the highest energy conversion x x 2 Cu O-c,whereasPtnanoparticlesarerandomlydistributedon efficiency, highlighting its superior photoenergy conversion 2 the{111}facetofCu O-oandCu O-ecto(Figure2h−j).The capability (Figures 3c and S14). Steady-state PL and TRPL 2 2 corresponding EDS patterns further confirm the spatially measurements show that the Cu O-ecto sample exhibits 2 selective deposition of Pt and MnO (Figure S9), while the significantly reduced PL intensity compared with the other x absence of Pt on Cu O-c and MnO nanosheets on Cu O-o samples, indicating suppressed recombination of photogen- 2 x 2 corroborates facet-dependent charge accumulation (Figure erated charge carriers (Figure S15 and Figure 3d). S10). These results provide direct experimental evidence for Furthermore, TRPL analysis shows a prolonged average thecascadechargeflowandefficientelectron−holeseparation lifetime (6.62 ns for Cu O-ecto compared to 6.13 and 5.22 2 induced by the ternary facet junction in Cu O-ecto. ns for the other samples), suggesting slower recombination 2 Basedontheaboveexperimentalandtheoreticalresults,the kinetics and enhanced charge separation. formation of ternary facet junctions in Cu O-ecto was clearly To validate the role of the facet junction in promoting 2 confirmed, enabling the directional migration of photo- photogenerated charge separation, PEC urea synthesis tests generated electrons and holes. Motivated by the above were carried out via the co-reduction of CO and NO − in a 2 3 findings, photoelectrochemical measurements were conducted three-electrode system. Urea was quantified by the urease to evaluate charge separation and transfer efficiency.37,38 The decomposition method, while gaseous and liquid phase photocurrent responses and electrochemical impedance spec- byproducts (NH and NO −) were identified via gas 3 2 troscopy (EIS) reveal that Cu O-ecto delivers the highest chromatography and UV−vis spectroscopy (Figures S16 and 2 photocurrent density and the smallest charge transfer S17). Notably, no CO, H , or other C + gaseous byproducts 2 2 resistance, indicative of superior charge separation and were detected. Linear sweep voltammetry (LSV) shows that interfacial charge transfer efficiency (Figures S11 and S12). under visible-light irradiation, the photocurrent density is The surface charge transfer efficiency of Cu O-ecto, which markedly enhanced compared to dark conditions and is 2 reflects an intrinsic catalytic property of the material, was consistently higher under a CO than an Ar atmosphere, 2 quantified by comparing the photocurrent densities in the confirmingactiveparticipationofCO inthereaction(Figures 2 absenceandpresenceofanelectronsacrificialagent(K S O ). 4a, S18, and S19). 2 2 8 Based on this method, an average charge transfer efficiency of Moreover, we systematically evaluated the effect of catalyst 47.3% was obtained for Cu O-ecto (Figure 3a). This result loading on the performance of the photoelectrode. Cu O-ecto 2 2 3856 https://doi.org/10.1021/acsenergylett.6c00152 ACSEnergyLett.2026,11,3853−3860
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ACS Energy Letters http://pubs.acs.org/journal/aelccp Letter Figure4.(a)LSVcurvesunderArdark/lightandCO dark/lightforCuO-ecto;(b)ureaFEandformationrateoffivedifferentCuOcatalystsat 2 2 2 +0.03VvsRHE;(c)ureaFEandformationrateofCuO-ectoatvariousappliedpotentials;(d)productsindifferentelectrolytes(CO RR:0.1M 2 2 KHCO,NO−RR:0.1MKNO,NO−+CO RR:0.1MKNO,NO−+CO RR:0.1MKNO);(e)infraredsignalsduringPECureasynthesis 3 3 3 3 2 3 2 2 2 by CuO-ecto atdifferentreaction times. 2 exhibitsanoptimalperformanceat0.05mg·cm−2(FigureS20). performance of Cu O-ecto in PEC urea synthesis was 2 At low loading, incomplete coverage of the FTO substrate evaluated over a potential range of +0.23 to −0.17 V vs limits the density of exposed surface Cu active sites. Excessive RHE. Both FE and R display a volcano-type curve, with urea urea loading produces a thicker film, increasing electron transport optimal values of 0.97 ± 0.16 mmol·g −1·h−1 and 15.35 ± cat distance and recombination, thereby reducing urea synthesis 1.52% at 0.03 V vs RHE. Increasing the applied potential performance.Tofurtherclarifytheeffectofcrystalfaceteffects enhances NO − reduction, leading to a moderate increase in 3 on C−N coupling for PEC urea synthesis, repeated experi- the formation of byproducts NO − and NH (Figure S22). 2 3 mentswereconductedusingthesecatalysts.Theureasynthesis Notably,Cu O-ectoproducesminimalbyproductsandexhibits 2 performance exhibits a volcanic trend with the emergence of excellent operational stability over 20 h (Figure S23). Further the{110}and{111}crystalfacetsandthedisappearanceofthe characterization of Cu O-ecto after reaction revealed surface 2 {100} facets; Cu O transforms from a cubic to an octahedral reconstructionwiththeformationofCu0,whilethebulkphase 2 morphology,andboththeFE andR initiallyincreaseand remained Cu O (Figures S24−S27). urea urea 2 then decrease (Figure 4b). Among the catalysts, Cu O-ecto Single-variable-controlled experiments comparing PEC, 2 achievesthehighestFE andR .Moreover,comparedwith photocatalysis, and electrocatalysis demonstrate that PEC urea urea other catalysts, Cu O-ecto produces the least amount of achievesaureaproductionrateof0.97mmol·g −1·h−1,which 2 cat byproducts (Figure S21). Subsequently, the applied potential is nearly 1.9 and 24 times that of electrocatalysis and forureasynthesiswasoptimized.AsdisplayedinFigure4c,the photocatalysis, respectively, highlighting the synergistic effect 3857 https://doi.org/10.1021/acsenergylett.6c00152 ACSEnergyLett.2026,11,3853−3860
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ACS Energy Letters http://pubs.acs.org/journal/aelccp Letter of photogenerated carriers and applied bias (Figure S28). significantlypromotestheseparationanddirectionalmigration Control experiments confirm that CO or NO − are the sole of photogenerated charge carriers. This, in turn, facilitates 2 3 carbon and nitrogen sources for urea formation (Figure 4d). efficient C−N coupling between the CO and the NO −. 2 3 Furthermore, when NO − was employed as a nitrogen source Overall, this study not only highlights the critical role of facet 2 instead of NO −, only trace amounts of urea were detected. engineeringinmodulatingchargedynamicsbutalsoprovidesa 3 This result suggests that the intermediates generated during promising approach for the sustainable and selective synthesis thereduction of NO − to NO − mayplay a crucial rolein the of urea through carbon−nitrogen co-reduction. 3 2 C−N coupling process. ■ ToelucidatethereactionmechanismofPECureasynthesis, ASSOCIATED CONTENT in situ-FTIR were conducted to probe the reaction * sı Supporting Information intermediates at different reaction times. At 0.03 V vs RHE, The Supporting Information is available free of charge at infrared spectra were collected in the range of 1350 to 3250 https://pubs.acs.org/doi/10.1021/acsenergylett.6c00152. cm−1 over 60 min (Figure 4e). A distinct band at 3174 cm−1, attributedtoN−Hbendingvibrations,indicatestheformation Supplementary experimental details and results, materi- of urea or N-containing intermediates.39 The infrared band at als, and methods (PDF) 1396cm−1correspondsto*OCOspeciesafterCO activation, ■ 2 while bands at 1988 and 2032 cm−1 are assigned to *CO AUTHOR INFORMATION intermediates, key species in CO 2 reduction.40 Notably, a C− Corresponding Authors N stretching vibration at 1420 cm−1 gradually intensifies with Min Li − College of Environmental Science and Engineering, reaction time, suggesting the accumulation of C−N coupling intermediates.9 Additionally, a band at 2110 cm−1 is assigned Beijing Forestry University, Beijing 100083, China; Email: limin2022@bjfu.edu.cn to the *OCNO intermediate, which is considered a crucial species in the C−N coupling step toward urea formation.10 Tianyu Zhang − College of Environmental Science and Moreover, the signals located at 1420−1 and 2110 cm−1 are Engineering, Beijing Forestry University, Beijing 100083, China; Email: tzhang@bjfu.edu.cn stronger than those observed for the other sample (Figure Haohong Duan − Department of Chemistry, Tsinghua S39).Collectively,theseresultsprovidestrongevidenceofthe University,Beijing100084,China; orcid.org/0000-0002- C−N coupling pathway in PEC urea synthesis. 9241-0984; Email: hhduan@mail.tsinghua.edu.cn In addition, DFT calculations of the adsorption energy of Qiang Wang − College of Environmental Science and CO on different crystal facets of Cu O indicate that CO 2 2 2 Engineering, Beijing Forestry University, Beijing 100083, preferentially adsorbs on the {111} facet of Cu O (Figure 2 China;StateKeyLaboratoryofEfficientProductionofForest S30). XPS N 1s spectra further show that Cu O-ecto exhibits 2 Resources, Beijing Forestry University, Beijing 100083, the strongest nitrate-related signal, suggesting more effective initialNO −activation(FigureS31).Moreover,EPRmeasure- China; orcid.org/0000-0003-2719-2762; 3 Email: qiangwang@bjfu.edu.cn ments using TEMPO as a spin-trapping agent reveal clear signals of trapped electrons, and the signal intensity increases Authors with irradiation time, indicating that Cu O-ecto can be 2 Hong Liang − College of Environmental Science and effectively excited to generate electrons (Figure S32). Based Engineering, Beijing Forestry University, Beijing 100083, on our previous studies, we propose the following reaction China mechanism occurring on the surface of the ternary facet Zhiheng Li − College of Environmental Science and junction Cu O photocathode. First, CO and NO − are 2 2 3 Engineering, Beijing Forestry University, Beijing 100083, adsorbed on the catalyst surface. Under light irradiation, the China presence of facet junctions induces directional separation of Xiaowen Liu − College of Environmental Science and photogenerated electron−hole pairs. The electrons preferen- Engineering, Beijing Forestry University, Beijing 100083, tially accumulate on the {111} facet, where they drive the China reduction of CO and NO − into *CO and *NO 2 3 2 Xinhao Xu − College of Environmental Science and intermediates, respectively. These intermediates undergo the Engineering, Beijing Forestry University, Beijing 100083, first C−N coupling step to form the *CO−NH species. China Subsequently, through successive proton−electron transfer Shixin Yu − Beijing Key Laboratory of Lignocellulosic processes, *CO−NH further couples with *NO in a second 2 Chemistry, Beijing Forestry University, Beijing 100083, C−Ncouplingstep,eventuallyleadingtotheformationofurea China molecules. Wenfu Xie − College of Environmental Science and In summary, we systematically research the influence of the Engineering, Beijing Forestry University, Beijing 100083, crystal facet on the PEC performance of polyhedral Cu O 2 China catalysts for urea synthesis. By synthesizing and comparing Cu O catalysts with different exposed crystal facets, it was Complete contact information is available at: 2 foundthattheCu O-ectowith{100},{110},and{111}facets https://pubs.acs.org/10.1021/acsenergylett.6c00152 2 exhibits the best performance in PEC urea synthesis. Author Contributions Specifically, the Cu O-ecto catalyst achieved an FE of 2 15.35% and a urea yield of 0.97 mmol·g −1·h−1, significantly The manuscript was written through the contributions of all cat outperforming other Cu O samples with a single facet and authors.Allauthorshavegivenapprovaltothefinalversionof 2 binary facet junction. Mechanistic studies revealed that the the manuscript. Hong Liang: Formal analysis, Investigation, presence of a facet junction in Cu O-ecto induces a built-in Data curation, Investigation, Visualization, Writing−original 2 electric field and a cascade charge transfer pathway, which draft. Min Li: Conception, Funding acquisition, Project 3858 https://doi.org/10.1021/acsenergylett.6c00152 ACSEnergyLett.2026,11,3853−3860
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ACS Energy Letters http://pubs.acs.org/journal/aelccp Letter administration, Resources, Supervision, Writing−review and (12)Kim,C.;King,A.J.;Aloni,S.;Toma,F.M.;Weber,A.Z.;Bell, editing. Zhiheng Li: Data curation, Visualization. Xiaowen A. T. Codesign of an integrated metal-insulator-semiconductor Liu: Investigation, Data curation. Xinhao Xu: Investigation. photocathodeforphotoelectrochemicalreductionofCO 2 toethylene. Shixin Yu: Formal analysis. Wenfu Xie: Formal analysis. Energy Environ. Sci. 2023,16, 2968−2976. (13) Li, M.; Shi, Q.; Li, Z.; Xu, M.; Yu, S.; Wang, Y.; Xu, S. M.; Tianyu Zhang: Writing−review and editing. Haohong Duan: Duan,H.Photoelectrocatalyticsynthesisofureafromcarbondioxide Writing−review and editing. Qiang Wang: Funding acquis- and nitrate over a CuO photocathode. Angew. Chem., Int. Ed. Engl. ition,Projectadministration,Resources,Supervision,Writing− 2 2024, 63(33),No. e202406515. review and editing. (14) Pan, J.; Li, M.; Wang, Y.; Xie, W.; Zhang, T.; Wang, Q. Funding Advanced photoelectrocatalytic coupling reactions. Chin. J. Catal. 2025, 73, 99−145. This work was supported by the National Natural Science (15) Liang, H.; Li, M.; Li, Z.; Xie, W.; Zhang, T.; Wang, Q. FoundationofChina(52300125,52225003,22208021),the5· Photoelectrochemical CO reduction with copper-based photo- 5EngineeringResearch&InnovationTeamProjectofBeijing 2 cathodes. J. CO Util. 2024, 79,102639. 2 Forestry University (BLRC2023B04), the Fundamental (16) Li, M.; Yu, S.; Huang, H. Emerging polynary bismuth-based Research Funds for the Central Universities photocatalysts:Structuralclassification,preparation,modificationand (QNTD202506), and the Energy Revolution S&T Program applications. Chin.J. Catal.2024, 57, 18−50. of Yulin Innovation Institute of Clean Energy (No. (17) Cui, J.; Zhang, X.; Huang, H.; Yang, M.; Yang, B.; Yang, Q.; E411080705). Liang, S.; Sun, S. 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