The electrocatalytic CO 2 reduction reaction (CO 2 RR) can dynamise the carbon cycle by lowering anthropogenic CO 2 emissions and sustainably producing valuable fuels and chemical feedstocks.M ethanol is arguably the most desirable C 1 product of CO 2 RR, although it typically forms in negligible amounts.I no ur search for efficient methanolproducing CO 2 RR catalysts,w eh ave engineered Ag-Zn catalysts by pulse-depositing Zn dendrites onto Ag foams (PD-Zn/Ag foam). By themselves,Z na nd Ag cannot effectively reduce CO 2 to CH 3 OH, while their alloys produce CH 3 OH with Faradaic efficiencies of approximately 1%. Interestingly,w ith nanostructuring PD-Zn/Ag foam reduces CO 2 to CH 3 OH with Faradaic efficiency and current density values reaching as high as 10.5 %a nd À2.7 mA cm À2 ,r espectively.C ontrol experiments and DFT calculations pinpoint strained undercoordinated Zn atoms as the active sites for CO 2 RR to CH 3 OH in ar eaction pathway mediated by adsorbed CO and formaldehyde.S urprisingly,t he stability of the *CHO intermediate does not influence the activity.The electrocatalytic CO 2 reduction reaction (CO 2 RR) using renewable electricity is ap romising means to mitigate the rising levels of CO 2 in the atmosphere. [1] Methanol is possibly the most valuable C 1 product that can be generated from this process, [1, 2] as it can be used either as afeedstock, solvent, or fuel. [3] Although structurally simple,i ts production from CO 2 RR (CO 2 + 5H 2 O + 6e À ! CH 3 OH + 6OH À )i sp oor in terms of selectivity and efficiency. Fore xample,A g, Au, Zn, Ni, Cu, and Pt reduce CO 2 into CH 3 OH with Faradaic efficiencies (FE) and current densities (j)b elow 1% and À0.1 mA cm À2 ,r espectively. [1] Thus,c onsiderable effort has been devoted to understanding how changes in composition and structure of metals as af unction of applied potential influence the rate of CO 2 RR to CH 3 OH.Nanostructuring and alloying of metals can increase the selectivity and efficiency for CO 2 RR to methanol and ethanol. Paris and Bocarsly used Ni 3 Al to produce C 1 to C 3 oxygenates in 0.1m K 2 SO 4 electrolyte. [4] CH 3 OH was formed with aFEof1%atapproximately À0.92 Vversus areversible hydrogen electrode (RHE). Hatsukade et al. reported that AgZn alloys catalyse the production of CH 4 and CH 3 OH with FE CH 3 OH being 0.85 %atÀ1.43 Vversus RHE. [5] Therein, Ag was proposed to reduce CO 2 to CO,while Zn stabilised *CHO intermediates (reduced from CO), such that more *CO is reduced to CH 3 OH. Dutta et al. reported that oxide-derived Cu foam catalysts have better selectivity toward highly hydrogenated CO 2 RR products;n amely ethane over ethylene. [6] They proposed that mesoporous foam structures can facilitate the readsorption of reaction intermediates or gas products for further reduction.Herein,w eh avep reparedapulse-deposited( PD) Zn catalyst on Ag foamswithhighactivityfor CO 2 RR to CH 3 OH. Thecatalystwas characterisedusing scanning electron microscopy (SEM),energy-dispersiveX-ray spectroscopy (EDS), Xraydiffraction(XRD),a...

Electrochemical reduction of CO (2) to value-added chemicals and fuels is a promising strategy to sustain pressing renewable energy demands and to address climate change issues. Direct observation of reaction intermediates during the CO (2) reduction reaction will contribute to mechanistic understandings and thus promote the design of catalysts with the desired activity, selectivity, and stability. Herein, we combined in situ electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy and ab initio molecular dynamics calculations to investigate the CORR process on Cu single-crystal surfaces in various electrolytes. Competing redox pathways and coexistent intermediates of CO adsorption (*CO atop and *CO bridge ), dimerization (protonated dimer *HOCCOH and its dehydrated *CCO), oxidation (*CO 2 − and *CO 3 2− ), and hydrogenation (*CHO), as well as Cu-O ad /Cu-OH ad species at Cu-electrolyte interfaces, were simultaneously identified using in situ spectroscopy and further confirmed with isotope-labeling experiments. With AIMD simulations, we report accurate vibrational frequency assignments of these intermediates based on the calculated vibrational density of states and reveal the corresponding species in the electrochemical CO redox landscape on Cu surfaces. Our findings provide direct insights into key intermediates during the CO (2) RR and offer a full-spectroscopic tool (40–4,000 cm −1 ) for future mechanistic studies.

The electrochemical CO and CO2 reduction reactions (CORR and CO2RR) using copper catalysts and renewable electricity hold promise as a carbon‐neutral route to produce commodity chemicals and fuels. However, the exact mechanisms and structure sensitivity of Cu electrodes toward C2 products are still under debate. Herein, we investigate ethylene oxide reduction (EOR) as a proxy to the late stages of CORR to ethylene, and the results are compared to those of acetaldehyde reduction to ethanol. Density functional theory (DFT) calculations show that ethylene oxide undergoes ring opening before exclusively reducing to ethylene via *OH formation. Based on generalized coordination numbers (CN), a selectivity map for the late stages of CORR and CO2RR shows that sites with moderate coordination (5.9 < CN < 7.5) are efficient for ethylene production, with pristine Cu(100) being more active than defective surfaces such as Cu(311). In contrast, kinks and edges are more active for ethanol production, while (111) terraces are relatively inert.

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We have employed in situ electrochemical shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) and density functional theory (DFT) calculations to study the CO reduction reaction (CORR) on Cu single-crystal surfaces under various conditions. Coadsorbed and structure-/potential-dependent surface species, including *CO, CuÀ O ad , and CuÀ OH ad , were identified using electrochemical spectroscopy and isotope labeling. The relative abundance of *OH follows a "volcano" trend with applied potentials in aqueous solutions, which is yet absent in absolute alcoholic solutions. Combined with DFT calculations, we propose that the surface H 2 O can serve as a strong proton donor for the first protonation step in both the C 1 and C 2 pathways of CORR at various applied potentials in alkaline electrolytes, leaving adsorbed *OH on the surface. This work provides fresh insights into the initial protonation steps and identity of key interfacial intermediates formed during CORR on Cu surfaces.