Synergistic Ru/B modulation of carbon nitride electronic structure for efficient photothermal CO2 catalysis

The rising levels of atmospheric CO 2 caused by industrial activities have led to escalating global climate challenges, calling for efficient and sustainable carbon mitigation strategies. However, conventional graphitic carbon nitride (g-C 3 N 4 )-based systems are hindered by low charge separation efficiency, limited visible-light absorption, and poor CH 4 selectivity, significantly restricting their catalytic performance. In this study, a novel photothermal catalyst‑ruthenium nanoparticle-loaded and boron-doped multilayered C 3 N 4 nanosheets (4Ru-3B-C 3 N 4 )-was synthesized via supramolecular self-assembly, NaBH 4 -assisted impregnation, and thermal calcination. The structure, composition, and optoelectronic characteristics were systematically characterized through XRD, FTIR, SEM/TEM, XPS, UV–vis DRS, PL, EIS, and in situ DRIFTS, while the reaction mechanism and electronic structure were confirmed using density functional theory (DFT) calculations and work function simulations. Compared to pristine C 3 N 4 , the multilayered nanosheet architecture, B-doping, and anchoring of Ru nanoparticles synergistically facilitate the provision of active sites and promote the separation of photogenerated charge carriers. Furthermore, combined with density functional theory (DFT) calculations, we demonstrate that the Ru nanoparticles serve as active centers, endowing the catalyst with enhanced CO 2 adsorption and activation capabilities, while lowering the overall reaction energy barrier for the conversion of CO 2 to CH 4 . Under photothermal CO 2 reduction conditions, 4Ru-3B-C 3 N 4 delivers a high CH 4 production rate of 266.6 μmol·g −1 ·h −1 , which is approximately 24 times that of pristine C 3 N 4 . The anchored Ru nanoparticles also contribute to the excellent cycling stability exhibited by the designed photocatalyst. This active surface engineering strategy provides a new perspective for developing high-performance catalysts for CO 2 photothermal reduction.