One-Step Synthesis of Ag-Cu Bimetallic Nanoparticles on p-Si Photoelectrodes for Solar-Driven CO2 Reduction

Inthe present work, we report the one-step synthesis of Ag x Cu100-x bimetallicnanoparticles (NPs) on p-type silicon (p-Si) supportsand their application as photocathodes for the photoelectrochemicalCO(2) reduction reaction (PEC-CO2RR). Based onthe metal-assisted chemical etching (MACE) of Si in HF medium, theproposed method allows the formation of NPs homogeneously distributedon the Si surface, with an excellent control of their bimetallic composition,surface coverage, and morphology by adjusting the experimental conditions(deposition time, precursor concentrations). Microstructural studiesreveal a phase-separated polycrystalline structure for the bimetallicwith a high dispersion of Ag and Cu nanocrystallites, remarkable forAg/Cu nanostructures synthesized by soft chemistry. The analysis ofthe PEC-CO2RR shows a better performance of Ag50Cu50/p-Si than Ag/p-Si and Cu/p-Si, with an onset potentialshift of 840 mV and a ratiometric power saved of & SIM;3% comparedto an analogous metal electrode in CO2 saturated 0.5 MNaHCO3. Photoelectrolysis tests under 1 sun illuminationcoupled with gas chromatography demonstrate the capacity of the bimetallicphotocathode to guide the selectivity with the applied potential.Thus, CO2 conversion to CO and CH4 is achievedon Ag50Cu50/p-Si, with a maximum Faradaic efficiency(FE) of 26% and 18.2% at -0.72 and -0.87 V-RHE, respectively. These values are consistent with recent researchon Ag-Cu systems on Si for the PEC-CO2RR but areobtained at significantly lower overpotentials. These are the firstresults ever reported for the PEC-CO2RR on p-Si photocathodesdecorated with AgCu NPs. The proposed deposition method is inexpensive,easily scalable, and can be extended to any bimetallic system whoseelements are compatible with MACE of Si.

Automated summary

In this study, one-step synthesis of AgxCu100-x bimetallic nanoparticles (NPs) on p-type silicon (p-Si) supports is reported, and their application as photocathodes for the photoelectrochemical CO2 reduction reaction (PEC-CO2RR) is explored. The proposed method allows for the homogeneous distribution of NPs on the Si surface, with excellent control of their bimetallic composition, surface coverage, and morphology. The Ag50Cu50/p-Si photocathode shows better performance than Ag/p-Si and Cu/p-Si, achieving CO2 conversion to CO and CH4 with high Faradaic efficiency at lower overpotentials.