“双碳”目标下，利用清洁可再生的太阳能驱动CO₂资源化利用成为重要的研究课题，但已有报道多以高纯CO₂为研究对象，而实际燃煤电厂排放的烟气中CO₂体积分数仅为3%～15%，为规避高能耗的CO₂提浓过程，直接实现低浓度CO₂光催化定向转化对节能减排及其资源化利用具有重要科学意义。采用共沉淀−水热法首先制得钴铝层状双氢氧化物(CoAl-LDH)，通过表面浸渍耦合氢气热处理将钌纳米颗粒负载至CoAl-LDH表面，构筑出可见光催化剂Ru/CoAl-LDH，其独特的表面组成与结构特性有助于实现以水为氢源的低浓度CO₂深度光还原。利用X射线衍射、透射电镜、X射线光电子能谱与紫外可见漫反射光谱等测试技术对复合催化剂的结构组成和微观形貌进行测定分析，结果表明：负载的钌物种为零价金属态Ru，其负载未改变 CoAl-LDH的纳米片状形貌，但可显著提升复合催化剂的光响应性能。以Ru/CoAl-LDH为光催化剂、水为电子给体和氢源、10% CO₂/N₂混合气体为模拟烟道气，在可见光照射下考察Ru负载量对还原产物生成量及深度还原产物甲烷选择性的影响，其中1.6% Ru/CoAl-LDH具有最优的CO₂光还原性能，可见光照射3 h后的甲烷产生量及选择性高达452.4 μmol/g和86.3%，分别是单一CoAl-LDH的10.4倍和3.3倍。同时，借助CO₂吸附等温线、原位XPS、瞬态光电流与阻抗谱等测试结果探究了Ru/CoAl-LDH对低浓度CO₂深度光还原的性能增强机理。CoAl-LDH表面的—OH基团利于复合催化剂对低浓度CO₂的选择性吸附；CoAl-LDH优异的水氧化性能可为CO₂深度光还原提供充足的原位氢源，无需使用具有爆炸危险性的氢气；负载的Ru作为光电子受体，在增强光生电荷分离与迁移效率的同时，作为CO₂还原活性位能实现其多电子还原过程。因此，CoAl-LDH和助催化剂Ru的协同作用是低浓度CO₂深度光还原性能得以提升的主要原因，复合催化剂Ru/CoAl-LDH实现了可见光水氧化与低浓度CO₂深度还原的有效耦合，为本质安全且低能耗CO₂转化体系的构建提供了重要理论指导，也为燃煤烟气CO₂资源化利用提供了新思路。

Under the dual-carbon goal, the resource utilization of CO₂ driven by clean and renewable solar energy has become an important research topic. However, the previous reports have mostly used high-purity CO₂ as the research object, while the CO₂ concentration in the flue gas emitted by coal-fired power plants is only 3%～15%. To avoid the high-energy CO₂ enrichment process, photocatalytic directional conversion of low concentration CO₂ into high-valued fuels or chemicals has important scientific significance for energy saving, emission reduction and its resource utilization. Cobalt-aluminum layered double hydroxide (CoAl-LDH) was firstly prepared by coprecipitation-hydrothermal method and visible-light catalysts Ru/CoAl-LDH were constructed by loading ruthenium nanoparticles onto the surface of CoAl-LDH via surface impregnation coupled with hydrogen heat treatment. The unique surface composition and structural characteristics of Ru/CoAl-LDH composites are conductive to implement deep photoreduction of low concentration CO₂ using H₂O as the hydrogen source. Structural composition and micro-morphology of the composite catalysts Ru/CoAl-LDH were determined by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and ultraviolet-visible diffuse reflection spectroscopy. The results indicate that the loaded Ru species is zero valence state of metal Ru. Loading Ru has no effect on the nano-lamellar morphology of CoAl-LDH, but can significantly improve the photoresponse performance of composite catalysts. By using Ru/CoAl-LDH as photocatalysts, H₂O as electron donor and hydrogen source, and 10% CO₂/N₂ mixture as simulated flue gas, the effect of Ru loading amount on the productivity of CO₂ reduction products and the selectivity of deep reduction products were investigated under visible light irradiation. 1.6% Ru/CoAl-LDH exhibited the optimal CO₂ photoreduction performance. After 3h of visible light irradiation, the productivity and selectivity of deep reduction product methane reached 452.4 μmol/g and 86.3%, which were 10.4 and 3.3 times of single CoAl-LDH, respectively. Meanwhile, the performance enhancement mechanism on deep photoreduction of low concentration CO₂ was explored by using CO₂ adsorption isotherms, in-situ XPS, transient photocurrent and impedance spectroscopy. The –OH groups on the surface of CoAl-LDH facilitate selective adsorption of composite catalysts for low concentration CO₂. Excellent H₂O oxidation performance of CoAl-LDH can provide sufficient in-situ hydrogen source for deep photoreduction of CO₂, without the use of H₂ having explosive risk. As the photoelectron acceptor, the loaded Ru can not only enhance the separation and migration efficiency of photogenerated charges, but also implement multi-electron reduction as active reductive sites of CO₂. Therefore, the synergistic effect of CoAl-LDH and cocatalyst Ru is the primary reason for the improvement of low concentration CO₂ deep photoreduction performance. The composite catalysts Ru/CoAl-LDH realize the effective coupling of visible-light water oxidation and low concentration CO₂ deep reduction, providing important theoretical guidance for the construction of essentially safe and low-energy consumptive CO₂ conversion system. It also provides a new idea for the resource utilization of CO₂ from coal flue gas.