Photoreforming lignocellulose to hydrogen over noble-metal-free Ni(OH)2/Cd0.5Zn0.5S nanotwins

Abstract

We report a photocatalytic system that utilizes Cd0.5Zn0.5S nanotwins decorated with various Ni-based co-catalysts for solar-driven hydrogen production through lignocellulose reformation. In this noble-metal-free system, Ni(OH)2 emerges as the most effective Ni form in enhancing the photocatalytic evolution of H2. By optimizing the composition with 3 wt% Ni(OH)2 loading, we achieved the highest activity, with the hydrogen production rates of 7.00 mmol g−1 h−1 and 1.97 mmol g−1 h−1 from α-cellulose and waste straw photoreforming, respectively. This optimized composition exhibited the highest quantum efficiency of 7.68%. In principle, the lower potential of Ni2+/Ni compared to the conduction band of Cd0.5Zn0.5S facilitates the transfer of electrons from the conduction band of Cd0.5Zn0.5S to Ni(OH)2. Specifically, during the photocatalytic reaction, a fraction of surface Ni(OH)2 is reduced to Ni. The in-situ formed Ni clusters, along with the Ni(OH)2, enhance the separation photogenerated electrons and facilitate their transfer to H+, leading to significantly improved photocatalytic activity. This work not only provides an effective strategy for developing more efficient photocatalysts, but also offers a direct means of harnessing clean energy from abundant waste biomass on Earth.