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 RuNPs/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.