No abstract

No abstract

Developing highly efficient semiconductor photocatalysts for H2 evolution is intriguing, but their efficiency is subjected to the following three critical issues: limited light absorption, low carrier separation efficiency, and sluggish H2 evolution kinetics. Element surface doping is a feasible strategy to synchronously break through the above limitations. In this study, we prepared a series of Co-surface-doped ZnS photocatalysts to systematically investigate the effects of Co surface doping on photocatalytic activity and electronic structure. The implantation of Co results in the emergence of the impurity level above the valence band (VB) and the upshifted conduction band (CB) and enhances its visible light absorption. Co gradient doping inhibits the combination and facilitates the migration of carriers. S atoms are proven to be reactive active sites for photocatalytic H2 evolution over both ZnS and Co-doped ZnS. Co doping alters the surface electronic structure and decreases the absolute value for the hydrogen binding free energy (ΔG H) of the adsorbed hydrogen atom on the catalyst. As a consequence, Co-surface-doped ZnS shows boosted photocatalytic H2 evolution activity relative to the undoped material. This work provides insights into the mechanistic understanding of the surface element doping modification strategy to developing efficient photocatalysts.

Photodegrading toxic organic pollutants in effluents over semiconductor photocatalysts is friendly and promising. The key is to develop a universally powerful and stable photocatalyst. In this work, highly efficient AgIO 3 @X heterojunction photocatalysts, composed of AgI and AgIO 3 two phases, are fabricated via a facile in situ reduction method. AgIO 3 is reduced and then AgI is generated on the surface of AgIO 3 , so the interfacial interaction between AgI and AgIO 3 is very intimate. Introduction of AgI on the surface of AgIO 3 extends the photoabsorption from an ultraviolet region to a visible region and also greatly improves charge transfer, giving rise to the remarkedly enhanced photocatalysis activity under visible-light excitation over AgIO 3 @X samples relative to the pristine AgIO 3 . The methyl orange (MO) photodegradation rate constant of the optimal AgIO 3 @20% photocatalyst reaches 0.175 min −1 under visible-light illumination (λ > 420 nm), about 86.5-fold enhanced compared with the pristine counterpart, outperforming most of previously reported state-of-the-art photocatalysts. Particularly, after 20 min of natural sunlight irradiation with a light intensity of 13.8 mW/cm 2 , the AgIO 3 @20% sample can rapidly decompose 81.1% of MO. The as-obtained composite photocatalysts also exhibit excellent photocatalytic activity against rhodamine B (RhB) and 2,4-dichlorophenol (2,4-DCP) under the illumination of visible light. The possible reaction pathways and the MO degradation mechanism have been systematically investigated and illustrated. The study paves a new way for designing and developing efficient visible-light-driven photocatalysts with an intimate interfacial interaction.