因缺乏合理有效的利用途径，大量低浓度瓦斯（${C_{{rm{C}}{{rm{H}}_{rm{4}}}}} $ < 30%）被直接排放，研究开发低浓度瓦斯高值转化利用方法和技术对保障煤矿安全生产与减缓温室效应具有重要意义，也是实现我国“双碳”战略目标必不可缺少的部分。以低浓度瓦斯为碳源制取液体燃料甲醇被认为是其理想的利用途径之一，以清洁太阳能为驱动力的光催化技术可在室温常压下活化转化甲烷，为低浓度瓦斯低碳利用提供新途径。首先采用水热法制备AgVO₃，以硫代乙酰胺为硫源，通过阴离子交换策略在AgVO₃表面原位复合Ag₂S，构筑出Ag₂S/AgVO₃异质结，改变硫代乙酰胺的用量可调控Ag₂S复合比例。利用XRD、SEM、TEM和紫外可见漫反射光谱等对复合催化剂的微观结构进行表征分析，以体积比为1∶12的甲烷/空气混合物模拟低浓度瓦斯，系统研究了Ag₂S复合比例、氧化剂用量、光照强度等对甲烷转化、甲醇产生及其选择性的影响规律，借助瞬态光电流响应谱和电子顺磁共振谱（EPR）探究了Z型异质结构Ag₂S/AgVO₃对增强模拟瓦斯转化性能的内在机理。研究结果表明：所制AgVO₃呈纤维状形貌，其晶相结构为单斜相，原位复合的Ag₂S呈纳米颗粒形态，其平均粒径为60 nm，且Ag₂S颗粒均匀分布于AgVO₃纤维表面。与单一AgVO₃和Ag₂S相比，复合材料Ag₂S/AgVO₃具有更强的光吸收性能，AgVO₃的带隙能、价带与导带电势分别为2.08 eV、2.21 V和0.13 V，Ag₂S的带隙能、价带与导带电势分别为0.91 eV、0.34 V和−0.57 V。与AgVO₃相比，复合催化剂Ag₂S/AgVO₃具有显著增强的瓦斯转化性能，可见光照射1 h最优催化剂20% Ag₂S/AgVO₃的甲烷转化和甲醇产生量为3.10 mmol/g和2.45 mmol/g，分别为单一AgVO₃的1.72倍与2.63倍，且其甲醇选择性高达78.9%；6次循环试验结果表明：Ag₂S/AgVO₃具有优异的催化稳定性。能带结构分析与EPR测试结果表明：Ag₂S/AgVO₃异质结遵循Z型电荷迁移机制，这不仅增强了光生电荷的空间分离，同时使其具有较强的氧化/还原能力，显著提升低浓度瓦斯定向转化制取甲醇的催化性能，为低浓度瓦斯低碳高效利用提供新思路。

Large number of low-concentration gas (${C_{{rm{C}}{{rm{H}}_{rm{4}}}}} $ < 30%) is discharged directly due to the lack of reasonable and effective utilization pathways. Research and development of high-value conversion and utilization methods and technologies for low-concentration gas is of great significance to ensure the safe production in coal seams and mitigate the greenhouse effect, and it is also an indispensable part of realizing China’s “double carbon” strategic goal. The production of liquid fuel methanol from low-concentration gas as a carbon source is considered to be one of the ideal utilization pathways. Photocatalytic technology driven by clean solar energy can activate and convert methane at room temperature and atmospheric pressure, providing a novel approach for low-carbon utilization of low-concentration gas. AgVO₃ was firstly prepared by hydrothermal method. Ag₂S/AgVO₃ heterojunction was constructed by in-situ decoration of Ag₂S on the surface of AgVO₃ via ion exchange strategy using thioacetamide as a sulfur source. Molar ratio of Ag₂S could be regulated by varying the amount of thioacetamide. The microstructure of composite catalysts was characterized using XRD, SEM, TEM and UV-Vis diffuse reflectance spectroscopy. A methane-air mixture with a volume ratio of 1∶12 was used as the simulated low-concentration gas, and the effects of Ag₂S compound ratio, oxidant concentration and light intensity on methane conversion, methanol productivity and selectivity were systematically investigated. The intrinsic mechanism of Z-type heterojunction Ag₂S/AgVO₃ for enhancing the conversion performance of simulated gas was explored by means of transient photocurrent response spectroscopy and electron paramagnetic resonance (EPR) spectroscopy. The results indicated that, the prepared AgVO₃ shown a fibrous morphology with monoclinic crystalline phase structure. The in-situ composite Ag₂S was in the form of nanoparticles with an average particle size of 60 nm, and the Ag₂S particles were uniformly distributed on the surface of AgVO₃ fibers. Composite Ag₂S/AgVO₃ exhibited enhanced light absorption compared to single AgVO₃ and Ag₂S. The bandgap energy, valence band and conduction band potentials of AgVO₃ were 2.08 eV, 2.21 V and 0.13 V, and those of Ag₂S were 0.91 eV, 0.34 V and −0.57 V, respectively. The composite catalyst Ag₂S/AgVO₃ shown significantly enhanced gas conversion performance compared to AgVO₃. The methane conversion and methanol production of the optimal catalyst 20% Ag₂S/AgVO₃ irradiated with visible light for 1 h was 3.10 mmol/g and 2.45 mmol/g, which was 1.72 times and 2.63 times higher than that of the single AgVO₃, respectively, and the methanol selectivity was up to 78.9%. The result of 6 cyclic tests shown the excellent catalytic stability of Ag₂S/AgVO₃. The results of energy band structure analysis and EPR test shown that, the Ag₂S/AgVO₃ heterojunction followed the Z-type charge transfer mechanism, which not only enhanced the spatial separation of photogenerated charges, but also maintained strong oxidation-reduction ability, which significantly improved the catalytic performance in the directional conversion of low concentration gas to methanol, and provided a novel idea for the high-efficiency utilization of low-concentration gas in a low-carbon way.