Crystalline MoS2-enhanced conductive black titania for efficient solar to chemical energy conversion: photocatalytic CO2 reduction and CH4 oxidation

Abstract

Here we report a facile direct solid-state reaction strategy employing crystalline MoS₂-coupled conductive black titania (BT) to synthesize nanocomposites with substantial BT–MoS₂ synergy. BT–MoS₂ shows a typical surface V_o-rich crystalline-core@amorphous-shell structure, wide-spectrum solar light response, remarkable solar to thermal conversion efficiency, and electron modification for solar energy conversion towards photocatalytic CO₂ reduction and CH₄ oxidation. Notably, the optimized BT–MoS₂ exhibits a superior CH₄ space-time yield of 18.1 μmol g⁻¹ h⁻¹ and selectivity of 80.6% for solar-driven CO₂ reduction. Furthermore, an alcohol (methanol and ethanol) yield of 121.1 μmol g⁻¹ h⁻¹ and overall selectivity of 96% for CH₄ oxidation and excellent photostability are achieved. In situ infrared analysis reveals the significant role of the activated surface-adsorbed species of ·CH₃ and ·OH radicals for downstream generation of alcohols and proves the indispensable effect of MoS₂ for constraining CH₄ overoxidation. The five-step H₂O₂-assisted photocatalytic CH₄ oxidation mechanism is demonstrated by the free radical reaction and carbon chain growth over BT–MoS₂.