Water Vapor‐Enhanced Selective Production of Methane During Photothermal CO ₂ Reduction: Mechanistic Insights Into Boron‐Doped Nickel Catalysts

The development of efficient CO 2 reduction technologies is crucial for mitigating climate change and advancing sustainable energy systems. In this study, the photothermal catalytic reduction of CO 2 to methane (CH 4 ) using boron‐doped Ni as a catalyst, focuses on enhancing product selectivity through reaction parameter optimization. Notably, addition of water vapor substantially improves both CH 4 yield (195.85 mmol g·h −1 ) and selectivity (80.21%), representing a significant advancement over traditional approaches. Through integrated experimental characterization and density functional theory (DFT) calculations, the underlying mechanism involving competitive adsorption dynamics is elucidated between CO 2 and H 2 O molecules on the boron‐doped Ni surface, along with their parallel dissociation pathways. DFT calculations also confirm that boron doping upshifts the Ni d‐band center, strengthening CO adsorption for subsequent hydrogenation. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements indicated that the reverse water‐gas shift (RWGS) reaction on boron‐doped Ni proceeded primarily via a dissociation pathway. Furthermore, the introduction of H 2 O enables alternative CO 2 reduction mechanisms through the carboxylate and bicarbonate pathways. This study demonstrates the significant potential of boron‐doped Ni catalysts for enhanced CO 2 methanation and provides valuable mechanistic insights into how reaction parameters influence the photothermal CO 2 reduction process.