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

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 mu mol g(-1) h(-1) and selectivity of 80.6% for solar-driven CO2 reduction. Furthermore, an alcohol (methanol and ethanol) yield of 121.1 mu mol 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 center dot CH3 and center dot 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.