Photothermal Regulation of Reaction Intermediates at Ru–O–Mn(II) Interfaces for Enhanced Low-Temperature CO2 Methanation

Abstract

Photothermal CO2 methanation offers a promising strategy for carbon-neutral fuel production. However, simultaneously achieving high activity, selectivity, and long-term stability at low temperatures remains challenging due to inherent trade-offs in reaction kinetics and competing pathways. Herein, we report a photothermal Ru/MnO catalyst featuring well-defined Ru–O–Mn(II) interfacial junctions, where Ru sites drive H2 dissociation, while the interface enhances CO2 adsorption, enabling efficient cleavage of HCOO* intermediates for further methanation at low temperatures. Under photothermal conditions, the optimized Ru/MnO-3 catalyst achieves a CH4 productivity of 64.79 mmol·g–1·h–1 with 31.5% CO2 conversion at 175 °C, significantly outperforming its thermally driven counterpart. In situ Fourier-transform infrared (FTIR) spectroscopy combined with density functional theory (DFT) calculations reveals temperature-dependent reaction behavior: at low temperatures, photothermal excitation lowers the kinetic barrier for formate transformation through enhanced hydrogen activation, whereas at elevated temperatures, the reaction increasingly favors CO*-involving pathways dominated by thermal effects. This photothermally induced modulation of reaction pathways, together with enhanced CO2 adsorption at Ru–O–Mn(II) interfaces and efficient H2 activation, underpins the observed low-temperature performance. Our findings provide mechanistic insights into photothermal CO2 methanation and highlight interfacial engineering as an effective strategy for designing low-temperature photothermal catalysts.