Nitrogen-doped biochar assists rapid electron transfer at the ZnCdS/CoMoO interface to enhance photocatalytic hydrogen production.

The interphase charge carrier transport rate in the photocatalytic H evolution reaction represents one of the parameters influencing the photocatalytic hydrogen generation performance. Sunflower straw, which is considered as farm waste and urea to prepare N-doped biochar (NC) co-catalysts, and construction of a composite catalyst ZnCdS/CoMoO-8/5 %NC for photocatalytic hydrogen production by in situ growth of CoMoO and biochar loaded on ZnCdS. Using 10 vol% lactic acid as the sacrificial reagent, the composite catalyst produced 701 μmol of hydrogen over 5 h of photocatalysis. This yield represents 8.09-fold and 64.03-fold enhancements compared to pure ZnCdS and CoMoO, respectively. Raman spectroscopy analysis revealed that the periphery of the carbon framework in the biochar after N-doping was perturbed, thereby generating additional active sites for the photocatalytic H evolution reaction. Through density-functional theory simulations and photoelectrochemical analyses, the introduction of NC was found to enhance photogenerated carrier migration. The ZnCdS/CoMoO-8/5 %NC composite system forms a Z-scheme heterojunction, wherein heterojunction construction and biochar mediation synergistically promote directional migration of photogenerated charge carriers and enhance interfacial charge separation efficiency in the composite catalyst. The strategy of converting agricultural waste into efficient co-catalysts for resource recycling provides a new approach for the application of biochar in photocatalysis.