Photo-deposition of Ni(OH)2/Ni onto twinned Cd0.5Zn0.5S for superior photocatalytic H2 evolution

Solar photocatalytic hydrogen evolution (PHE) from water is broadly considered as one of perfect paths to obtain green hydrogen. Ni(OH)2 and Ni dual cocatalysts were simultaneously anchored on twinned Cd0.5Zn0.5S (CZS) by one-step photo-deposition to obtain Ni(OH)2/Ni/CZS. The Ni(OH)2/Ni/CZS catalyst exhibits superior PHE activity with 104.5 mmol g−1 h−1 in Na2S/Na2SO3 system under visible light. The quantum yield is 50.1 % at 420 nm. Furthermore, the Ni(OH)2/Ni/CZS displays conspicuous PHE with 80.0 mmol g−1 h−1 in the sacrificial reagent system and 21.7 μmol·g−1 h−1 in pure water under sunlight, indicating its great practical application potential. Theoretical DFT calculations and experimental measurements demonstrate that Ni(OH)2 and Ni have a synergism on improving PHE properties of CZS, Ni serves as a water reduction co-catalyst for H2 evolution while Ni(OH)2 mainly does as hole (h+) traps (oxidation co-catalyst) to catalyze the reaction between h+ and sacrificial agent. The twinned CZS could establish electric fields to facilitate the separation of photo electrons (e−) and h+. Here, we emphasize two synergisms for highly-effective solar hydrogen-evolution from water: (I) Surface and bulk photo-charge separations of CZS are simultaneously enhanced via anchored Ni(OH)2/Ni cocatalysts and twin-crystals homojunction. (II) Surface oxidation and reduction half-reactions are catalyzed by loaded Ni(OH)2 and metal Ni, respectively.