Elucidating structure and function of Ni/La-doped-ceria catalysts for CO2 reduction by the reverse water gas shift reaction
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Reducing and/or utilizing CO2 in the atmosphere is mandatory to decrease its negative effects as greenhouse gas. The reverse water gas shift reaction (rWGS) is one of the most promising routes for CO2 valorization. Here, we show that Ni/La-doped ceria catalysts, prepared by the solution combustion synthesis method, has an excellent catalytic performance per unit mass of catalyst. Structure-activity correlations obtained using a combination of different techniques such as X-ray and neutron diffraction, Raman spectroscopy, in-situ NAP-XPS, Electron Microscopy, and catalytic testing, point out to optimum values for the Ni loading and the La proportion. Density functional theory calculations of the elementary steps of the reaction on model Ni/ceria catalysts aid toward the microscopic understanding of the active sites nature. Metallic Ni activates H2 dissociation and a certain La doping maximizes Ce3+ sites, which supplies greater available oxygen to form H2O. These findings are essential for the rational design of highly efficient and selective rWGS catalysts.
作为温室气体，大气中二氧化碳(CO₂)的减排与资源化利用是缓解其负面影响的必要手段。逆水煤气变换反应(reverse water gas shift reaction, rWGS)是CO₂资源化利用的极具潜力的技术路径之一。本研究表明，采用溶液燃烧合成法(solution combustion synthesis)制备的镍掺杂镧氧化铈(Ni/La-doped ceria)催化剂，具备优异的单位质量催化性能。通过联用X射线与中子衍射(X-ray and neutron diffraction)、拉曼光谱(Raman spectroscopy)、原位近常压X射线光电子能谱(in-situ NAP-XPS)、电子显微镜(Electron Microscopy)以及催化性能测试等多种表征手段获得的构效关系，揭示了镍负载量与镧掺杂比例的最优取值。针对模型Ni/氧化铈催化剂上反应基元步骤的密度泛函理论(density functional theory, DFT)计算，有助于从微观层面阐明活性位点的本质。金属态镍可活化氢气的解离过程，而适量的镧掺杂可最大化三价铈(Ce³+)位点数量，进而提供更多可利用的氧物种以生成水分子(H₂O)。上述研究发现对于合理设计高效且高选择性的rWGS催化剂具有至关重要的指导意义。
