Exploring high efficiency S-scheme heterojunction photocatalysts with strong redox ability for removing volatile organic compounds from the air is of great interest and importance. However, how to predict and regulate the transport of photogenerated carriers in heterojunctions is a great challenge. Here, density functional theory calculations were first used to successfully predict the formation of a CdS quantum dots/InVO₄ atomic-layer (110)/(110) facet S-scheme heterojunction. Subsequently, a CdS quantum dots/InVO₄ atomic-layer was synthesized by in-situ loading of CdS quantum dots with (110) facets onto the (110) facets of InVO₄ atomic-layer. As a result of the deliberately constructed built-in electric field between the adjoining facets, we obtain a remarkably enhanced photocatalytic degradation rate for ethylene. This rate is 13.8 times that of pure CdS and 13.2 times that of pure InVO₄. In-situ irradiated X-ray photoelectron spectroscopy, photoluminescence and time-resolved photoluminescence measurements were carried out. These experiments validate that the built-in electric field enhanced the dissociation of photoexcited excitons and the separation of free charge carriers, and results in the formation of S-scheme charge transfer pathways. The reaction mechanism of the photocatalytic C₂H₄ oxidation is investigated by in-situ electron paramagnetic resonance. This work provides a mechanistic insight into the construction and optimization of semiconductor heterojunction photocatalysts for application to environmental remediation.

Development of metal oxide semiconductors-based methane sensors with good response and low power consumption is one of the major challenges to realize the real-time monitoring of methane leakage. In this work, a self-assembled mulberry-like ZnO/SnO₂ hierarchical structure is constructed by a two-step hydrothermal method. The resultant sensor works at room temperature with excellent response of ~56.1% to 2000 ppm CH₄ at 55% relative humidity. It is found that the strain induced at the ZnO/SnO₂ interface greatly enhances the piezoelectric polarization on the ZnO surface and that the band bending results in the accumulation of chemically adsorbed O₂^- ions close to the interface, leading to significant improvement in the sensing performance of the methane gas sensor at room temperature.

The use of heterojunctions is a promising solution to the problem of cross-sensitivity in gas sensors. In this work, a carbon monoxide sensor based on the CuO/TiO₂ heterojunction was designed and fabricated. Due to the good adsorption properties of CuO materials to CO, and the heterojunction interface charge transfer, the CuO/TiO₂ thin film sensor exhibits high sensitivity to CO at room temperature. The response is as high as 10.8–200 ppm CO, about 10 times its response to H₂. Interference from H₂ is greatly reduced by optimizing the structure of the CuO/TiO₂ heterojunction. This reliable detection of carbon monoxide with excellent discrimination against H₂ is of great significance for the development of CO gas sensors.

Low electronic conductivity and large volume changes during the (de) lithiation process are the two main challenges for ZnO anode materials used for lithium-ion batteries (LIB). Here, a free-standing, flexible, and binder-free LIB electrode composed of ZnO nanorods and carbon cloth (CC) is fabricated. This is then decorated with Ag nanoparticles and finally coated by an amorphous carbon layer to form the hybrid electrode: (C@(Ag&ZnO)). The voids among the nanorods are sufficient to accommodate the volume expansion of the ZnO while the flexible CC, which acts as the current collector, relieves the volume change-induced stress. The Ag nanoparticles are effective in improving the conductivity. This composite electrode shows excellent LIB performance with a stable long cycling life over 500 cycles with a reversible capacity of 1093 mAh g⁻¹ at a current density of 200 mA g⁻¹. It also shows good rate performance with reversible capacity of 517 mAh g⁻¹ under a high-current density of 5000 mA g⁻¹. In situ Raman spectroscopy is conducted to investigate the contributions of the amorphous carbon layer to the capacity of the whole electrode and the synergy between the CC and ZnO nanorods.