Bi–Sn\nCo-Catalyst-Modified p‑Si Nanowire\nArray Photocathodes for Photoelectrocatalytic CO₂ Reduction\nto Formate

Abstract

Co-catalyst modification has been studied as a strategy\nto enhance\nsilicon nanowires’ (SiNWs’) photoelectrocatalytic performance\nfor CO₂ reduction since their high light absorption efficiency\nand unique radial structure facilitate electron transport. However,\ntheir limited activity and poor selectivity toward CO₂ reduction\nremain a challenge. Herein, we report the fabrication of core–shell\nstructured, non-noble metal Bi and Sn co-catalyst-loaded SiNW photoelectrodes\nfor CO₂ reduction to formate. Microscopic morphology results\nrevealed that Bi co-catalysts were deposited as nanoparticles and\nSn co-catalysts as thin films on Bi and Si surfaces. Notably, Bi–Sn/SiNW\nphotocathodes showed enhanced formate yield and selectivity compared\nto electrodes modified with only Bi or Sn. Specifically, at −1.02\nV vs reversible hydrogen electrodes, the Faraday efficiency of formate\nreached 88.67% and the product rate was 80.07 μmol h^–1 cm^–2. Further experimental analysis and computational\nresults demonstrated that the reasonable band structure formed by\nSi and the two co-catalysts Bi and Sn improved migration of photogenerated\nelectrons, thus promoting CO₂ reduction reaction toward\nformate with high efficiency and selectivity. This work lays the foundation\nfor composite photocathodes with multiple co-catalysts for synergistic\ncatalysis, addressing the challenges related to CO₂ reduction\nand sustainable energy development.