Surface‐Plasmon‐Assisted Photoelectrochemical Reduction of CO₂ and NO₃⁻ on Nanostructured Silver Electrodes

Abstract Electrochemical reduction of carbon dioxide (CO₂) typically suffers from low selectivity and poor reaction rates that necessitate high overpotentials, which impede its possible application for CO₂ capture, sequestration, or carbon‐based fuel production. New strategies to address these issues include the utilization of photoexcited charge carriers to overcome activation barriers for reactions that produce desirable products. This study demonstrates surface‐plasmon‐enhanced photoelectrochemical reduction of CO₂ and nitrate (NO₃⁻) on silver nanostructured electrodes. The observed photocurrent likely originates from a resonant charge transfer between the photogenerated plasmonic hot electrons and the lowest unoccupied molecular orbital (MO) acceptor energy levels of adsorbed CO₂, NO₃⁻, or their reductive intermediates. The observed differences in the resonant effects at the Ag electrode with respect to electrode potential and photon energy for CO₂ versus NO₃⁻ reduction suggest that plasmonic hot‐carriers interact selectively with specific MO acceptor energy levels of adsorbed surface species such as CO₂, NO₃⁻, or their reductive intermediates. This unique plasmon‐assisted charge generation and transfer mechanism can be used to increase yield, efficiency, and selectivity of various photoelectrochemical processes.