WS 2 /g-C 3 N 4 composite as an efficient heterojunction photocatalyst for biocatalyzed artificial photosynthesis.

A heterogeneous WS 2 /g-C 3 N 4 composite photocatalyst was prepared by a facile ultrasound-assisted hydrothermal method. The WS 2 /g-C 3 N 4 composite was used for photocatalytic regeneration of NAD + to NADH, which were coupled with dehydrogenases for sustainable bioconversion of CO 2 to methanol under visible light irradiation. Compared with pristine g-C 3 N 4 and the physical mixture of WS 2 and g-C 3 N 4 , the fabricated WS 2 /g-C 3 N 4 composite catalyst with 5 wt% of WS 2 showed the highest activity for methanol synthesis. The methanol productivity reached 372.1 μmol h -1 g cat -1 , which is approximately 7.5 times higher than that obtained using pure g-C 3 N 4 . For further application demonstration, the activity of the WS 2 /g-C 3 N 4 composite catalyst toward photodegradation of Rhodamine B (RhB) was evaluated. RhB removal ratio approaching 100% was achieved in 1 hour by using the WS 2 /g-C 3 N 4 composite catalyst with 5 wt% of WS 2 , at an apparent degradation rate approximately 2.6 times higher than that of pure g-C 3 N 4 . Based on detailed investigations on physiochemical properties of the photocatalysts, the significantly enhanced reaction efficiency of the WS 2 /g-C 3 N 4 composite was considered to be mainly benefiting from the formation of a heterojunction interface between WS 2 and g-C 3 N 4 . Upon visible-light irradiation, the photo-induced electrons can transfer from the conduction band of g-C 3 N 4 to WS 2 , thus recombination of electrons and holes was decreased and the photo-harvesting efficiency was enhanced.