Sulfur-vulcanized CoFe2O4 with high-efficiency photo-to-thermal conversion for enhanced CO2 reduction and mechanistic insights into selectivity

Semiconductor photocatalysts often exhibit low CO 2 reduction activity due to inherent limitations. Photothermal (PTT) processes have emerged as crucial for enhancing this activity, yet investigations in this area remain sparse. This study introduces a novel CoFe 2 O 3.5 S 0.5 photothermal catalyst, synthesized via hydrothermal methods with particle sizes ranging from 5 to 10 nm. Comparative analysis reveals that the CO yield from the as-prepared catalyst surpasses that of CoFe 2 O 4 by 8.9 times, achieving 100% selectivity. The integration of sulfur significantly boosts near-infrared light absorption and promotes the conversion of light to thermal energy, enabling the catalyst to reach 185 °C within 300 ss. This rapid temperature escalation facilitates the swift separation of charge carriers. Additionally, the adsorption of CO 2 and the dynamics of surface intermediates were thoroughly examined using in situ FTIR spectroscopy and theoretical models, identifying COOH* as the pivotal intermediate and the bottleneck in the reaction pathway. Our findings rectify gaps in prior studies and offer a foundational reference for further exploration of product selectivity in the photocatalytic reduction of CO 2 .