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将温室气体CO_2催化加氢转化为CH_4,有利于碳资源化利用和减轻环境污染,是具有一定现实意义的模型化反应.实验发现,氧化物负载型催化剂对CO_2甲烷化过程展现出较高的催化活性和稳定性,但其催化机理和界面作用机制并未得到清楚认识.基于DFT+U计算方法,本文系统研究了复合氧化物Ce_(0.75)Zr_(0.25)O_2负载Ni体系催化CO_2甲烷化复杂基元过程.结果表明,在Ni/Ce_(0.75)Zr_(0.25)O_2(110)体系中,CO_2甲烷化反应涉及CO_2分解和甲酸盐两条途径,且CO_2的分解途径占主导地位,整个反应的控制步骤为CO_2吸附过程.产物甲烷是由界面上CO_2解离加氢产生的CH基团进一步在金属Ni活性位上加氢生成,揭示了该催化体系中载体与负载物之间存在协同催化作用,即载体界面主要发生碳氧化物的脱氧加氢,碳氢中间物种的加氢反应在Ni上发生.
The catalytic hydrogenation of CO_2 to CH_4 is beneficial to the utilization of carbon resources and the reduction of environmental pollution, which is of practical significance. It was found that the CO_2 methanation process exhibited a higher Catalytic activity and stability, but its catalytic mechanism and interface mechanism have not been clearly understood.Based on the DFT + U calculation method, the catalytic activity of CO 2 methanation on Ce_ (0.75) Zr_ (0.25) O_2 composite Ni Complex elementary process.The results show that CO 2 methanation involves CO 2 decomposition and formate in Ni / Ce 0.75 Zr 0.25 O 2 (110) system, and the decomposition pathway of CO 2 is the dominant one, The control step of the whole reaction is CO 2 adsorption process, and the product methane is further hydrogenated on the active site of metal Ni by CH group produced by CO 2 dissociation hydrogenation at the interface, revealing that there exists between the support and the support in the catalytic system The synergistic catalysis, that is, the deoxidation and hydrogenation of carbon oxides mainly occurs at the interface of the carrier, and the hydrogenation reaction of hydrocarbon intermediate species occurs on Ni.