| Cd1-xZnxS is one of the most extensively studied sulfides solid solution due to itscontrollable band structure and excellent performance under visible light irradiation. However,the efficiency of photocatalytic H2evolution for these solid solutions is far from satisfyinglevel owing to the rapid recombination of photo-generated electrons and holes inphotocatalysts. POMs exhibit remarkably rich redox and photochemical properties. Ourrecent researches found that POMs could act as electron acceptors to promote the powerconversion efficiency of semiconductor thin-film solar cells.Composite photocatalysts K7HNb6O19(Nb6)-NiS/Cd0.65Zn0.35S were synthesized using afacile coprecipitation-surface loading strategy. It is shown that the activity of Cd0.65Zn0.35S isenhanced by the presence of the polyoxoniobate K7HNb6O19(Linqvist structure, denoted asNb6) and NiS as cocatalysts. The H2evolution rate is increased to3.4times that ofCd0.65Zn0.35S and2.6times that of NiS/Cd0.65Zn0.35S. The excellent photocatalytic activity ofNb6-NiS/Cd0.65Zn0.35S is even higher than that on Nb6-Pt/Cd0.65Zn0.35S.The as-prepared Nb6-NiS/Cd0.65Zn0.35S sample reached a high H2evolution rate of7.59mmol h-1g-1with2wt%Nb6and1%NiS loaded and the QY of42%at420nm. This workrepresents a significant advance in preparation of Cd1-xZnxS based composite catalysts forphotocatalytic H2evolution by using POMs and transition-metal sulfide as cocatalysts. Tooptimize the photocatalytic conditions for the highest hydrogen yield, the amount of Nb6andNiS loaded on NiS/Cd0.65Zn0.35S have been investigated.Among POMs, polyoxoniobates are of particular interest for photocatalysis becausesome dense niobates have been used for overall water-splitting photocatalysts. Recently,several molecular photocatalytic systems based on polyoxoniobates and polytantalotungstateshave been studied for water splitting into H2. K8Ta6O19-NiS/Cd0.65Zn0.35S sample reached ahigh H2evolution rate of6.29mmol h-1g-1,which is also higher than that of Cd0.65Zn0.35S.The above experimental results show that the combination of semiconductors(Cd1-xZnxS)with the appropriate POMs can be greatly improve the activity of the photolysis of waterhydrogen production. POMs will be used widely in semiconductor-based photocatalytic H2production systems. |
