Interfacial Engineering of CN-B/Ti3C2 MXene Heterojunction for Synergistic Solar-Driven CO2 Reduction

Photocatalytic CO2 reduction holds great potential for sustainable solar fuel production, yet its practical application is often limited by inefficient charge separation and poor product selectivity. The photothermal effect presents a viable strategy to address these challenges by reducing activation energies and accelerating reaction kinetics. In this work, we report a rationally designed CN-B/Ti3C2 heterojunction that effectively leverages photothermal promotion for enhanced CO2 reduction. The black carbon nitride (CN-B) framework, synthesized via a one-step calcination of urea and Phloxine B, exhibits outstanding photothermal conversion, reaching 131.4 °C under 300 mW cm−2 illumination, which facilitates CO2 adsorption and charge separation. Coupled with Ti3C2 MXene, the optimized composite (3:1) achieves remarkable CO and CH4 production rates of 80.21 and 35.13 μmol g−1 h−1, respectively, without any cocatalyst—representing a 2.9-fold and 8.8-fold enhancement over CN-B and g-C3N4 in CO yield. Mechanistic studies reveal that the improved performance stems from synergistic effects: a built-in electric field prolongs charge carrier lifetime (3.15 ns) and reduces interfacial resistance, while localized heating under full-spectrum light further promotes CO2 activation. In situ Fourier transform infrared (FTIR) spectroscopy confirms the accelerated formation of key intermediates (*COOH and *CO). The catalyst also maintains excellent stability over 24 h. This study demonstrates the promise of combining photothermal effects with heterojunction engineering for efficient and durable CO2 photoreduction.