Anode Photovoltage Compensation-Enabled Synergistic CO₂ Photoelectrocatalytic Reduction on a Flower-Like Graphene-Decorated Cu Foam Cathode

An interconnected and hierarchically structured electrode composed of a Cu nanoparticle-modified flower-like reduced graphene oxide-decorated copper foam (Cu NP/f-RGO/CF) is crafted and exploited for photoelectrocatalytic (PEC) reduction of CO₂ in a TiO₂ nanotube photoanode-driven PEC cell. Anode photovoltage compensation confers a more negative cathode potential for CO₂ reduction, thus leading to a synergistic effect between photocatalysis (PC) and electrocatalysis (EC). CO₂ reduction rate under PEC condition is 5.4× higher than that of the simple sum under PC and EC processes. The well-defined flower structure of RGO in the CF scaffold effectively prevents its self-agglomeration, which increases its adsorption towards CO₂ with improved electron-transfer kinetics due to the 3D interconnected structure with abundant electron transfer pathways. DFT calculations further reveal the absorption and activation of CO₂ on Cu NP/f-RGO capitalize on the C-C bond with RGO and O-Cu bond with Cu NPs, thereby leading to a bended and stretched structure. The enhanced CO₂ adsorptivity and activation on the hierarchical Cu NP/f-RGO/CF electrode significantly improve CO₂ reduction and facilitate the conversion of C1 products to high-order products. This research highlights the great prospect of anode photovoltage compensation enables synergistic photoelectrocatalysis and 3D hierarchical electrode for CO₂ drastic reduction into high-order products.