Supporting Information Stabilization of unconventional body-centered tetragonal phase in copper nanowires for efficient carbon dioxide electroreduction to multi-carbon products
Materials. Cupric chloride dihydrate (CuCl2·2H2O, 99.99%), D-(+)-glucose (C6H12O6, ≥ 99.5%), hexadecylamine (HDA, 90%), octadecylamine (ODA, 90%), oleylamine (OAm, 70%, technical grade), (1R,2R)-(-)-1,2-diaminocyclohexane ((R,R)-DACH, 98%), trioctylphosphine oxide (TOPO, 99%), potassium bicarbonate (KHCO3, ≥ 99.99% metals basis), n-hexane (anhydrous, 99.5%), ethanol (anhydrous, ≥ 99.9%), and toluene (99.5%) were purchased from Aladdin. Cuprous bromide (CuBr, 98%) and oleic acid (OA, 99%) were purchased from Sigma-Aldrich.
Synthesis of bct/fcc Cu NWs-30. 84 mg of CuCl2·2H2O, 200 mg of glucose, and 720 mg of HDA were added to 40 mL of water and stirred overnight. The mixture was then transferred into a 100 mL Teflon-lined autoclave and heated at 120 °C for 6 h. After cooling, the product was washed with DI water and centrifuged 1-2 times to remove most of HDA. After centrifugation, the product was redispersed in 20 mL of deionized water and subjected to ultrasonication. Subsequently, 10 mL of toluene were added, resulting in a biphasic system. The tube was vigorously vortexed for more than 20 s, followed by standing for approximately 5 min. The upper organic layer was collected, centrifuged, and washed with ethanol 2-3 times. Finally, the product was redispersed in 3 mL of ethanol.
Synthesis of bct/fcc Cu NWs-80. 90.9 mg of CuCl2·2H2O, 105.6 mg of glucose, and 860 mg of ODA were added to 40 mL of water and stirred overnight. The mixture was then transferred into a 100 mL Teflon-lined autoclave and heated at 120 °C for 24 h. Purification same as Cu NWs-30.
Synthesis of bct/fcc Cu NWs-200. 340 mg of CuCl2·2H2O and 396 mg of glucose were dissolved in 40 mL DI water (solution A). 140 mg of (R,R)-DACH were first dissolved in 5 mL of OAm, then 8.75 mL of ethanol and 100 μL of OA were introduced (solution B). In a 20 mL glass vial, 0.6 mL of solution B was first added. Under vigorous magnetic stirring, 3 mL of solution A were then introduced. After homogenization, 8.4 mL of water were added, and the mixture was stirred for 5 min. Subsequently, the solution was heated at 50 °C under magnetic stirring for 3 h, followed by transfer into an autoclave for further heating at 120 °C for 4 h.
Synthesis of fcc Cu NCs. 28.7 mg of CuBr, 193.3 mg of TOPO and 10 mL of OA were added into a 25 mL three-necked flask under stirring. The mixture was heated under N2 atmosphere to 80 °C and kept for 30 min. The obtained solution was then heated to 260 °C and incubated for 30 min. After cooling, the precipitate was centrifuged and washed three times with excess n-hexane. Then the products were washed by the mixture of n-hexane and ethanol with different volume ratios (5:1, 4:2, 1:1, 2:4, 1:5), and finally stored in ethanol.
Electrochemical CO2RR measurement in H-type cell. 100 µg of catalyst stock solution were centrifuged, and the obtained precipitate was redispersed into 96 µL of ethanol, followed by the addition of 4 µL of Nafion solution (5 wt%). 40 μL of catalyst ink were dropped onto glass carbon electrode (GCE, diameter 8 mm), containing 40 µg of Cu catalyst. Electrolyte: 0.1 M KHCO3 saturated with CO2, 8 mL in both anode and cathode chambers. CO2 flow rate: 30 sccm.