The construction of heterojunctions has been widely applied to improve the gas sensing performance of composites composed of nanostructured metal oxides. This review summarises the recent progress on assembly methods and gas sensing behaviours of sensors based on nanostructured metal oxide heterojunctions. Various methods, including the hydrothermal method, electrospinning and chemical vapour deposition, have been successfully employed to establish metal oxide heterojunctions in the sensing materials. The sensors composed with the built nanostructured heterojunctions were found to show enhanced gas sensing performance with higher sensor responses and shorter response times to the targeted reducing or oxidising gases compare with those of the pure metal oxides. Moreover, the enhanced gas sensing mechanisms of the metal oxide-based heterojunctions to the reducing or oxidising gases are also discussed, with the main emphasis on the important role of the potential barrier on the accumulation layer.

Effective detection of toxic and hazardous gases is crucial for ensuring human safety, and high-performance metal oxide-based gas sensors play an important role in achieving this goal. In₂O₃ is a widely used n-type metal oxide in gas sensors, and various In₂O₃ nanostructures have been synthesized for detecting small gas molecules. In this review, we provide a brief summary of current research on In₂O₃-based gas sensors. We discuss methods for synthesizing In₂O₃ nanostructures with various morphologies, and mainly review the sensing behaviors of these structures in order to better understand their potential in gas sensors. Additionally, the sensing mechanism of In₂O₃ nanostructures is discussed. Our review further indicates that In₂O₃-based nanomaterials hold great promise for assembling high-performance gas sensors.

The adsorption of H₂ on the pristine and Mo-doped graphene was investigated by density functional theory (DFT) calculations. The structural and electronic properties of H₂-graphene systems were studied to understand the interaction between H₂ molecule and graphene-based material. Our calculation results showed the pristine graphene was not an ideal sensing material to detect H₂ molecule as it ran far away from the pristine graphene surface. Different with pristine graphene, the Mo-doped graphene presented much higher affinities to the H₂ molecule. It was found that the placed H₂ molecules could stably be chemisorbed on the Mo-doped graphene with high binding energy. The electronic property of Mo-doped graphene was significantly affected by the strong interaction and orbital hybridization between H₂ and Mo-doped graphene sheet. The H₂ molecule would capture more charges from the doped graphene than the pristine system, indicating the higher sensitivity for the graphene doped with Mo.

First-principles DFT calculations have been employed to examine the hydrogen storage behavior of Ca-decorated silicene. A single Ca atom binds to the hollow site of the silicene monolayer with a binding energy of −2.348 eV, the magnitude of which exceeds the cohesive energy of bulk Ca, thus preventing Ca clustering. Pristine silicene interacts weakly with H₂, with an adsorption energy of only −0.047 eV, while Ca decoration notably enhances the binding affinity to −0.561 eV. Each Ca site can accommodate up to five H₂ molecules through a Kubas-like interaction, with an average adsorption energy of −0.327 eV. With Ca atoms decorating both sides of the silicene, the system delivers a hydrogen storage capacity of 7.5 wt% and complete H₂ release at approximately 380 K as revealed by AIMD simulations. Our findings suggest that Ca-decorated silicene could serve as a viable material for reversible hydrogen storage applications.