Controlled Synthesis And Photoelectrochemical Properties Of Tungsten-based Nanosheet Photoelectrode

The increasing exhaustion of fossil energy forces people to seek new ways to get renewable energy. W-based electrode material can be used for photoelectrocatalytic water splitting due to its appropriate band gap structure. However, the photoelectrochermical (PEC) activity of single W-based photoelectrode is still not ideal. Considering the above facts, this dissertation focuses on the enhancement of PEC activity of W-based photoelectrodes through new strategies, namely, modification of non-noble metal co-catalysts and construction of ternary heterojunctions. The main contents are as follows:(1) We found that the molecular complex of bipyridine-cobalt could significantly improve the PEC activity of WO3 nanosheet photoelectrode.The WO3 nanosheet photoelectrode with three-dimension structure was synthesized by a facile hydrothermal oxidation and subsequent post-calcination treatment process. Co-dipy/WO3 nanosheet composite photoelectrode was prepared by a direct hydrothermal precipitation route,using the as-synthesized WO3 nanosheet photoelectrode as the substrate.Compared with WO3 nanosheet photoelectrode, the PEC performance of the composite electrode was improved by 1.89 times in the 0.5 M Na2SO4 electrolyte at an applied voltage of 1.2 V (vs RHE). In addition, PEC performance of Co-dipy/WO3 composite photoelectrode was further enhanced by the adsorption of phosphate ions because of the role of phosphate ion as a proton acceptor in the process of PEC water splitting.The co-modification of molecular co-catalyst and phosphate ion provides a new strategy for designing new highly efficient photoelectrode.(2) We have constructed Pt/In2S3/CdS/WSe2 ternary heterojunction,which could obviously improve the PEC activity of WSe2 nanosheet photoelectrode. The p-type WSe2 nanosheet array electrode was prepared by a chemical vapor deposition method. CdS/WSe2 heterojunction was prepared by a simple water bath deposition, using the WSe2 nanosheet photoelectrode as the substrate. In order to avoid the photocorrosion of CdS and enhance the surface catalytic activity of the electrode, we further prepared Pt/In2S3/CdS/WSe2 by a water bath deposition and subsequent photoelectric deposition. The photocatalytic activity of WSe2 was improved by 4.2 times at an applied voltage of 0.1 V (vs RHE) in 0.5 M Na2SO4 electrolyte.(3) We developed an effective non-noble metal co-catalyst CoSe2,which could significantly enhance PEC activity of WSe2. CoSe2/WSe2 was prepared by a hydrothermal deposition route by using the as-synthesized WSe2 nanosheet photoelectrode as the substrate. PEC activity of WSe2 was improved by 4.72 times at an applied voltage of 0.1 V (vs RHE) in 0.5 M Na2SO4 electrolyte, which was comparable to that of Pt/WSe2.