Highly sensitive and selective gas sensors with low energy consumption and amenable to miniaturization are required for real-time gas monitoring applications. The challenge is to produce sensing units at a sufficiently low cost to allow for broad deployment, which can only be reached with efficient materials and fabrication procedures. In this context, metal oxides are promising for next-generation gas sensors due to their high surface-area-to-volume ratio, efficient electron transfer, enhanced and tunable surface reactivity, fast response, and short recovery time. However, sensors from metal oxides are normally not sufficiently selective and have to be operated at high temperatures. These limitations have been overcome with strategies such as doping with other oxides, UV-illumination, and noble metal decoration. This review concentrates on the design and mechanisms of heterostructures for gas sensors, which are obtained with metal oxides in conjunction with other materials (e.g. other metal oxides and 2D materials). The key topics discussed include: (a) synthesis of metal oxide heterostructures (MOHs); (b) semiconducting heterostructures comprising n–n, n–p, and p–p heterojunctions, with emphasis on their sensing mechanisms; (c) sensors produced with heterostructures involving 2D materials. The challenges and prospects for gas sensors based on MOHs are also discussed.

实时气体监测应用需要具有低能耗且易于小型化的高灵敏度和选择性气体传感器。面临的挑战是以足够低的成本生产传感单元以允许广泛部署，这只能通过有效的材料和制造程序来实现。在这种情况下，金属氧化物具有高表面积与体积比、高效电子转移、增强和可调表面反应性、快速响应和短恢复时间等优点，有望用于下一代气体传感器。然而，由金属氧化物制成的传感器通常没有足够的选择性，必须在高温下运行。这些限制已经通过掺杂其他氧化物、紫外线照射和贵金属装饰等策略得到克服。本综述集中于气体传感器异质结构的设计和机制，这些异质结构是通过金属氧化物与其他材料（例如其他金属氧化物和 2D 材料）结合获得的。讨论的关键主题包括： (a) 金属氧化物异质结构 (MOH) 的合成；(b) 包含 n-n、n-p 和 p-p 异质结的半导体异质结构，重点是它们的传感机制；(c) 用涉及二维材料的异质结构生产的传感器。还讨论了基于 MOH 的气体传感器的挑战和前景。(b) 包含 n-n、n-p 和 p-p 异质结的半导体异质结构，重点是它们的传感机制；(c) 用涉及二维材料的异质结构生产的传感器。还讨论了基于 MOH 的气体传感器的挑战和前景。(b) 包含 n-n、n-p 和 p-p 异质结的半导体异质结构，重点是它们的传感机制；(c) 用涉及二维材料的异质结构生产的传感器。还讨论了基于 MOH 的气体传感器的挑战和前景。