Zn1−xCdxS nanowall photoanode prepared via seed layer epitaxial growth method and modified by dual co-catalyst for photoelectrochemical water splitting

Abstract

Exploring novel preparation methods and controlling the morphology as well as the ratio of metal ions are important for the ternary sulfide photoelectrode in photoelectrochemical (PEC) water splitting. In this paper, the novel Zn1−xCdxS nanowall film photoanodes were firstly prepared by seed layer epitaxial growth method, and its x can be adjusted to 0.2, 0.5, 0.8. The effects of different growth solution on seed layer and epitaxial growth layer were studied. The reaction mechanism of synthesis route was investigated. The Zn0.2Cd0.8S nanowall has the best PEC performances than that of other ratios of Zn: Cd, and its photocurrent density is 0.20 mA∙cm−2 at 0.9 V vs. RHE under simulated sunlight. Subsequently, in order to increase the photo-excited carrier separation efficiency of Zn0.2Cd0.8S to promote the oxidation reaction, the hole storage layer (NiOOH) and the hole transfer layer (Co-Pi) were loaded. The photo-excited holes are captured, collected and directed to the Helmholtz layer to react with the electrolyte by the hole storage layer and hole transfer layer, respectively. The photocurrent density of Zn0.2Cd0.8S/NiOOH/Co-Pi photoelectrode is 1.9 times of that of Zn0.2Cd0.8S, which is 0.39 mA∙cm−2 at 0.9 V vs. RHE under simulated sunlight. Zn0.2Cd0.8S/NiOOH/Co-Pi shows excellent stability relative to Zn0.2Cd0.8S, they corrode to 93% and 78% respectively. This photoelectrode construction method and dual layer co-catalyst mechanism provide a new way for PEC water splitting of sulfide.