Engineering plasmon-enhanced cathode for photo-electrocatalytic conversion of CO₂: Insight into the activity trends

Photoelectrochemical CO₂ reduction into valuable fuels (syngas, formic acid) is a promising strategy to mitigate carbon emissions. The existing challenges include poor stability, high charge recombination, moderate-to-low Faradaic efficiencies of the photoelectrode, and mass-transport limitation in the classical H-cells. In this study, we decorated plasmonic Ag metal over Bi₂WO₆/ZnIn₂S₄ (ABZ) heterostructure, to prepare a photocathode and systematically tested their performances under light with an intensity of 126.3 mWcm^-2. Bi₂WO₆ exhibited the highest total current density (-9.14±0.4 mAcm^-2) with H₂ca.8.10μmolcm^-2h^-1, and HCOOH ca.9.55μmolcm^-2h^-1 as major products at -0.69 V vs. RHE. At large applied potentials, the generation rate of HCOOH was reduced. Hydrophobic ABZ catalyst outperformed the tested catalysts with the highest 15.4±0.3cm² electrochemical surface area, reaching a total of ca. 100% Faradaic efficiency for CO-rich syngas, at -0.99 V vs. RHE. These findings, combined with results from in situ Diffuse reflectance infrared Fourier transform (DRIFT) Spectroscopy and extensive electrochemical characterizations, present a strategy for tailoring liquid and gaseous products in a CO₂ photo-electroreduction reaction harvesting visible light.