Synthesis And Hydrogen-evolution Performance Of Highly Efficient And Stable Cd S Photocatalysts

CdS semiconductor has drawn extensive attentions in the field of photocatalysis owing to its suitable bandgap for visible-light absorption and strong reduction potential for hydrogen evolution.However,the bare CdS usually shows a decreased hydrogen evolution activity because of its photocorrosion.In this study,to develop highly stable and efficient CdS photocatalytic materials for hydrogen production,the interfacial modulation and surface modification of CdS are explored:?1?facile synthesis and hydrogen-evolution performance of highly efficient cubic-phase CdS nanocrystals;?2?the synergistic effect of Ti???-hole cocatalyst and Ni???-electron cocatalyst for the enhanced photoinduced-stability and photocatalytic activity of CdS.First,cubic-phase CdS nanocrystal photocatalysts were prepared by a facile precipitation method in a sulfur-enriched ambient.It was found that the synthetic environment has a great influence on the surface structure of cubic-phase CdS nanocrystals.When the Na2S and Na2SO3 were used as the precursors,a large amount of S^2-/SO₃^2-ions were adsorbed on the CdS nanocrystal surface.The photocatalytic results indicated that the cubic-phase CdS nanocrystals displayed an efficient photocatalytic H₂-evolution activity,which was remarkably higher than that of the hexagonal-phase CdS by a factor of 5.7.On the basis of the experimental results,a possible mechanism was proposed to account for the improved photocatalytic activity of cubic-phase CdS nanocrystals,namely,the absorbed S^2-/SO₃^2-on CdS surface not only can easily capture the H⁺from water to promote the interfacial H₂-evolution reaction,but also rapidly capture the photogenerated holes of CdS surface to enhance its photoinduced stability,resulting in the improved photocatalytic performance.Second,amorphous Ti??? as an effective hole cocatalyst was successfully loaded on the CdS surface to prepare Ti???/CdS photocatalyst by a facile impregnation method.The photocatalytic results indicated that compared with the naked CdS,the resultant Ti???/CdS photocatalysts exhibited an obviously enhanced photocatalytic stability?a decreased deactivation rate from 37.9%to 13.5%?in addition to its limited improvement?37.4%?of photocatalytic activity.To further improve its photocatalytic performance,the amorphous Ni???as an electron cocatalyst was modified on the surface of Ti???/CdS to prepare the dual amorphous-cocatalyst modified Ti???-Ni???/CdS photocatalyst.As a consequence,the photocatalytic activity and stability of CdS can be greatly improved by simultaneous modification of amorphous Ti???and Ni???due to their synergistic effect,namely,the Ti???hole-cocatalyst can effectively reduce the photocorrosion effect of CdS by rapidly transferring the interfacial photogenerated holes,while the Ni???electron-cocatalyst first can rapidly capture the photogenerated electrons and then function as the reduction active site to promote the interfacial H₂-evolution reaction.