Zinc cadmium sulphide-based photoreforming of biomass-based monosaccharides to lactic acid and efficient hydrogen production

Approaches that add value to biomass through the use of photoreforming reactions offer great opportunities for the efficient use of renewable resources. Here, we constructed a novel zinc cadmium sulphide/molybdenum dioxide-molybdenum carbide–carbon (Zn x Cd 1-x S-y/MoO 2 -Mo 2 C-C) heterojunction which was applied to photoreforming of biomass-based monosaccharides for hydrogen and lactic acid production. Bandgap engineering effectively modulated the redox capacity of Zn x Cd 1-x S-y and exposed more (101) crystalline surfaces, which improved the lactic acid selectivity. The MoO 2 -Mo 2 C-C (MC) co-catalysts had unique microstructures that increased the light absorption range and the number of active sites of Zn x Cd 1-x S-y. These features effectively promoted the separation and migration of photogenerated carriers, which in turn enhanced the photoreforming activity. The optimised Zn 0.4 Cd 0.6 S-0/MC composites exhibited superior photocatalytic activity with a hydrogen yield of 12.2 mmol/g/h. Conversion of biomass-based monosaccharides was approximately 100 %, where xylose had the greatest lactic acid selectivity (64.1 %). Active species, including h + , ⋅O 2 − , ⋅OH, and 1 O 2 , all favoured lactic acid production, where ⋅O 2 − played a major role in the conversion. This study demonstrates that rational design of photocatalysts can achieve the selective conversion of biomass into high value-added chemicals as well as the generation of clean energy.