Bismuth-based compounds platforms: From fundamentals to chemiresistive gas sensor applications

With the rapid evolution of Internet of Things (IoT) technology, digital transformation is deeply driving the innovation of rapid detection systems in environmental monitoring, medical diagnosis, and food safety. Gas-sensitive materials are the core units of gas sensors, and metal oxide-based gas sensors with high sensitivity, low cost, and easy integration have been used in these scenarios. Among them, bismuth-based compound materials are potential candidates for gas sensors because their unique layered structure (providing abundant active sites to accelerate gas diffusion and surface reactions), tunable electronic properties (multivalent properties, such as Bi₂O₃ (Bi³⁺) and BiVO₄ (Bi⁵⁺), which can be doped or compounded to regulate their redox activities, and flexibly adapt to the adsorption and reaction needs of different gases), and non-toxicity. However, the current research still faces challenges such as insufficient performance, unclear sensing mechanism, and practical application bottleneck, and it is urgent to fully understand the intrinsic correlation of preparation-structure-performance-mechanism. In this review, we summarize the crystal structures and electronic characteristics of various bismuth-based compounds and clarify their relationship with gas-sensing properties. The preparation, performance, enhancement strategies, gas sensing mechanism, and practical applications of Bi₂O₃, Bi₂S₃, Bi₂WO₆, BiFeO₃, Bi₂MoO₆, and Bi₂O₂CO₃-based gas sensors are reviewed in detail. On the basis, the challenges faced by the chemical gas sensors based on bismuth compounds are provided, as well as the insights into future focus. This review will provide a new idea for the development and research direction of bismuth-based compound gas sensors, and further promote their practical application in emerging scenarios.