Gradient Hydrogen Migration Modulated with Self-Adapting S Vacancy in Copper-Doped ZnIn₂S₄ Nanosheet for Photocatalytic Hydrogen Evolution

Abstract

It is a challenge to regulate charge flow synergistically at the atomic level to modulate gradient hydrogen migration (H migration) for boosting photocatalytic hydrogen evolution. Herein, a self-adapting S vacancy (Vs) induced with atomic Cu introduction into ZnIn 2 S 4 nanosheets was fabricated elaborately, which can tune charge separation and construct a gradient channel for H migration. Detailed experimental results and theoretical simulations uncover the behavior mechanism of Vs generation with Cu introduction after substituting a Zn atom tendentiously. Cu−S bond shrinkage and Zn−S bond distortion are presented around Vs areas. Besides, Vs induced by Cu introduction lowers the internal electric field to restrain electron transmission between layers, which are enriched on the Vs area because of the lower surface electrostatic potential. Atomic Cu and Vs show a synergistic effect for regulating regional charge separation due to the Cu dopant being a hole trap and Vs being an electron trap. The channels for H migration with gradient ΔG H 0 are constructed by different S atom sites, which are modulated by Vs. Gradient H migration driven by a photothermal effect occurs on an identical surface without striding across a heterogeneous interface, which is a valid pathway with lower resistance for boosting H 2 release. Ultimately, 5 mol % Cu confined in ZnIn 2 S 4 nanosheets achieves an optimum photocatalytic hydrogen evolution activity of 9.8647 mmol g −1 h −1 , which is 14.8 times higher than 0.6640 mmol g −1 h −1 for ZnIn 2 S 4 , and apparent quantum efficiency reaches 37.11% at 420 nm. This work demonstrates the behavior mechanism of atomic substitution and provides cognition for hydrogen evolution mechanism deeply.

Flower-Like Dual-Defective Z-Scheme Heterojunction g-C3N4/ZnIn2S4 High-Efficiency Photocatalytic Hydrogen Evolution and Degradation of Mixed Pollutants

“…Thus, it is further proved that there is an electronic interaction between pCN-N and ZIS-Z in the nanocomposite, which promotes the separation and transfer of photogenerated electron-hole pairs. According to the XPS analysis, it can be concluded that there is a strong interfacial coupling effect between the nitrogen-rich and oxygen-doped pCN-N and the zinc vacancy ZIS-Z (see Supplementary Materials Figure S3b for EPR analysis of zinc vacancies) to form a heterojunction structure [59,60], which further confirms the conclusions of XRD and FTIR. The formation of the heterojunction is beneficial to promote the separation and transfer of photogenerated electron and hole pairs, which is beneficial to improving the photocatalytic performance of pCN-N/ZIS-Z.…”

“…However, ZIS-Z has a flower-like structure with a large surface area that can fully contact degraded pollutants in the water. In addition, the Zn vacancies in ZIS-Z can be used as electron traps to enrich electrons to reduce the surface electrostatic potential [60]. Therefore, the electron-donating groups on the surface of methyl orange and metronidazole can be combined with the electron traps on the surface of ZIS-Z to enhance the ability of the catalyst in order to adsorb and contact pollutants, and further improve the catalytic degradation performance.…”

Defective Ultrathin ZnIn2S4 for Photoreductive Deuteration of Carbonyls Using D2O as the Deuterium Source

“…Thus, the S vacancy may act as an electron vortex to trap photoexcited electrons for charge balance. [ 21 , 36 , 42 ] Charge distributions are also clearly changed around the nearby In and Zn atoms, as can be seen from the blue and red colors appearing and vanishing, as we move farther away from the defect center. We then picked several In and S atoms around the S vacancy center and plotted their DOS as a function of energy in Figure 5F .…”

“…This shows that S vacancy will modify the ZIS electronic structure drastically by creating shallow trap states around the Fermi energy, which could promote interfacial electron transfer. [ 21 , 42 ]…”

Mechanical, optical, and thermoelectric properties of semiconducting ZnIn2X4 (X= S, Se, Te) monolayers

“…In the continued effort of the prediction and experimental fabrication of 2D semiconductors, most recently, Zhang et al [34] succeeded in fabricating the layered structure of ZnIn 2 S 4 using a hydrothermal method. They found that the ZnIn 2 S 4 2D system can be employed for photocatalytic hydrogen evolution.…”