Self-optimizing bifunctional CdS/Cu2S with coexistence of light-reduced Cu0 for highly efficient photocatalytic H2 generation under visible-light irradiation

Abstract A self-optimizing bifunctional core-shell CdS/Cu 2 S heterojunction with high activity and superb stability for the photocatalytic hydrogen evolution under visible light irradiation was synthesized by a simple two-step solvothermal method. Compared with pure CdS, the photocatalytic activity of the hybrid is significantly enhanced by almost 25 times. The sample CdS/Cu 2 S-30 has shown a maximum H 2 evolution rate of 14.4 mmol h −1  g −1 with an apparent quantum yield of 19.5% at 420 nm. The surface of single-crystalline CdS nanorod is fully covered by Cu 2 S, observed via SEM and TEM, which benefits the activity of catalyst by shorting radial transfer path of charge carriers and increasing the surface area for reaction. This photocatalyst features both bifunction and self-optimizing. During photo reaction, part of Cu 2 S is reduced to Cu 0 by irradiation on the surface between CdS core and Cu 2 S shell, while the rest of Cu 2 S offers plenty of active sites for hydrogen evolution reaction (HER). These generated Cu 0 retard the charge carrier recombination process by forming multi-heterojunction. Meanwhile, the self-optimizing of this photocatalyst is realized by Cu/Cu 2 S ratio on the surface of catalyst varying automatically to the optimal value to adapt to the corresponding reaction condition. Based on all these benefits, hydrogen evolution reaction is facilitated.