Synergistic Ru Species on Poly(heptazine imide) Enabling Efficient Photocatalytic CO₂ Reduction with H₂O beyond 800 nm

Abstract

Photocatalytic CO₂ conversion with H₂O to carbonaceous fuels is a desirable strategy for CO₂ management and solar utilization, yet its efficiency remains suboptimal. Herein, efficient and durable CO₂ photoreduction is realized over a Ru_NPs/Ru-PHI catalyst assembled by anchoring Ru single atoms (SAs) and nanoparticles (NPs) onto poly(heptazine imide) (PHI) via the in-plane Ru-N₄ coordination and interfacial Ru-N bonds, respectively. This catalyst shows an unsurpassed CO production (32.8 µmol h^-1), a record-high apparent quantum efficiency (0.26%) beyond 800 nm, and the formation of the valuable H₂O₂. Ru SAs tune PHI's electronic structure to promote in-plane charge transfer to Ru NPs, forming a built-in electron field at the interface, which directs electron-hole separation and rushes excited electron movement from Ru-PHI to Ru NPs. Simultaneously, Ru SAs introduce an impurity level in PHI to endow long-wavelength photoabsorption, while Ru NPs strengthen CO₂ adsorption/activation and expedite CO desorption. These effects of Ru species together effectively ensure CO₂-to-CO conversion. The CO₂ reduction on the catalyst is revealed to follow the pathway CO₂→ *CO₂→ *COOH→ *CO→ CO, based on the intermediates identified by in situ diffuse reflectance infrared Fourier transform spectroscopy and further supported by density functional theory calculations.