Synergism of interfacial Ti-O-Co bonds and surface Co2+/Co3+ redox couples on TiO2 for highly selective photocatalytic CO2 methanation

Co₃O₄/TiO₂ achieves a CH₄ yield of 34.8 μmol g −1  h −1 with 82.4% selectivity. • Ti–O–Co bonds serve as charge transfer channels in Co₃O₄/TiO₂. • Co 2+ /Co 3+ redox couples stabilize *CO intermediates and facilitate PCET. • Electron transfer promotes Co electron enrichment for *CO stabilization. • Synergistic electron transfer and proton supply promote selective CO₂ methanation. Value-added conversion of CO 2 using solar energy is a sustainable strategy to address the energy crisis and environmental issues simultaneously. In this work, Co 3 O 4 /TiO 2 composite photocatalysts were successfully prepared by a hydrothermal method. The optimized Co 3 O 4 /TiO 2 achieves a CH 4 yield of 34.8 μmol·g −1 ·h −1 with 82.4% selectivity. The enhanced catalytic activity is ascribed to interfacial Ti-O-Co bonds that facilitate electron transfer toward Co sites, thereby modulating the Co 2+ /Co 3+ electronic environment and creating relatively electron-rich Co sites for *CO stabilization, while the Co 3 O 4 component facilitates the proton-coupled electron transfer (PCET) process toward CH 4 formation. This study provides a practical strategy for promoting the value-added photocatalytic conversion of CO 2 using multivalent transition metal oxide composite photocatalysts. Co 3 O 4 /TiO 2 enables highly selective photoreduction of CO 2 into CH 4 . Ti-O-Co bonds serve as pathways transferring photogenerated electrons from TiO 2 to Co sites. The electron-rich Co centers act as active sites to stabilize *CO intermediates. Meanwhile, Co 3 O 4 promotes water oxidation and maintains sufficient proton supply, synergistically facilitating CH 4 production. Download: Download high-res image (200KB) Download: Download full-size image