Constructing g-c3 n4 /cd1−x znx s-based heterostructures for efficient hydrogen production under visible light

Abstract

Two types of photocatalysts, 1%Pt/Cd1−x Znx S/g-C3 N4 (x = 0.2–0.3) and Cd1−x Znx S/1% Pt/g-C3 N4 (x = 0.2–0.3), were synthesized by varying the deposition order of platinum, and a solid solution of cadmium and zinc sulfides onto the surface of g-C3 N4. The characterization of photo-catalysts showed that, for 1%Pt/Cd1−x Znx S/g-C3 N4, small platinum particles were deposited onto a solid solution of cadmium and zinc sulfides; in the case of Cd1−x Znx S/1%Pt/g-C3 N4, enlarged platinum clusters were located on the surface of graphitic carbon nitride. Based on the structure of the photocatalysts, we assumed that, in the first case, type II heterojunctions and, in the latter case, S-scheme heterojunctions were realized. The activity of the synthesized samples was tested in hydrogen evolution from triethanolamine (TEOA) basic solution under visible light (λ = 450 nm). A remarkable increase in hydrogen evolution rate compared to single-phase platinized 1%Pt/Cd1−x Znx S photocat-alysts was observed only in the case of ternary photocatalysts with platinum located on the g-C3 N4 surface, Cd1−x Znx S/1%Pt/g-C3 N4. Thus, we proved using kinetic experiments and characterization techniques that, for composite photocatalysts based on Cd1−x Znx S and g-C3 N4, the formation of the S-scheme mechanism is more favorable than that for type II heterojunction. The highest activity, 2.5 mmol H2 g−1 h−1, with an apparent quantum efficiency equal to 6.0% at a wavelength of 450 nm was achieved by sample 20% Cd0.8 Zn0.2 S/1% Pt/g-C3 N4.