Photoelectrochemical CO₂ Reduction toward Multicarbon Products with Silicon Nanowire Photocathodes Interfaced with Copper Nanoparticles

The development of photoelectrochemical systems for converting CO₂ into chemical feedstocks offers an attractive strategy for clean energy storage by directly utilizing solar energy, but selectivity and stability for these systems have thus been limited. Here, we interface silicon nanowire (SiNW) photocathodes with a copper nanoparticle (CuNP) ensemble to drive efficient photoelectrochemical CO₂ conversion to multicarbon products. This integrated system enables CO₂-to-C₂H₄ conversion with faradaic efficiency approaching 25% and partial current densities above 2.5 mA/cm² at -0.50 V vs RHE, while the nanowire photocathodes deliver 350 mV of photovoltage under 1 sun illumination. Under 50 h of continual bias and illumination, CuNP/SiNW can sustain stable photoelectrochemical CO₂ reduction. These results demonstrate the nanowire/catalyst system as a powerful modular platform to achieve stable photoelectrochemical CO₂ reduction and the feasibility to facilitate complex reactions toward multicarbons using generated photocarriers.