Vectorial carriers interfacial migration of Cd1-xZnxS heterophase junctions for visible-light water splitting

Abstract

Abstract Twin structure in Cd1-xZnxS solid solution based on sphalerite/wurtzite (ZB/WZ) heterophase junction is considered as a quite promising approach to enhance the charge separation efficiency and inhibit the charge recombination during the photocatalytic process. Herein, Cd1-xZnxS nanocrystals based on ZB/WZ heterophase junction with different molar ratios of Cd/Zn were synthesized by one-step solvothermal process. XRD analysis and HRTEM images verified the formation of nano-twin structures in the Cd0·6Zn0·4S solid solution. Photoluminescence (PL) spectra, time-resolved photoluminescence (TRPL) spectra, Electrochemical impedance spectroscopy (EIS) test and Photocurrent response revealed that the recombination of photogenerated charge carriers has been reduced due to the presence of ZB/WZ heterophase junction. The experimental results showed that the photocatalytic activity of Cd0·6Zn0·4S without noble metal load was the best under visible light irradiation, and the hydrogen production efficiency was up to 472\xa0μmol\xa0h−1 and an apparent quantum efficiency of 9.8% at 420\xa0nm. The periodic type-Ⅱ staggered energy band arrangement formed between ZB and WZ phases can orientate the photoinduced electrons and holes to ZB and WZ regions, respectively, and redox reactions can occur on the surface. Meanwhile, Cd0·6Zn0·4S exhibited good stability for hydrogen production. The result provides an available progress for the development of photocatalytic mechanism in heterophase junction between ZB and WZ phases, leading to the vectorial interfacial transfer of photogenerated e−/h+ pairs and prolonged carrier lifetime which can effectively enhance the photocatalytic reactivity.