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

- A core-shell CdS/Cu2S with high activity and superb stability was synthesized.
- This catalyst features self-optimization and bifunction during photocatalytic process.
- Self-optimization of Cu@CdS/Cu2S attributes to migration of charge carriers.
- Cu@Cu2S acting as bifunctional cocatalyst facilitates photocatalytic HER.

A self-optimizing bifunctional core-shell CdS/Cu2S 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/Cu2S-30 has shown a maximum H2 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 Cu2S, 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 Cu2S is reduced to Cu0 by irradiation on the surface between CdS core and Cu2S shell, while the rest of Cu2S offers plenty of active sites for hydrogen evolution reaction (HER). These generated Cu0 retard the charge carrier recombination process by forming multi-heterojunction. Meanwhile, the self-optimizing of this photocatalyst is realized by Cu/Cu2S 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.

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