基于碳化钼材料CO_(2)加氢制备高附加值化学品的热催化研究进展

Review on Using Molybdenum Carbides for the Thermal Catalysis of CO_(2) Hydrogenation to Produce High-Value-Added Chemicals and Fuels

CO_(2)加氢对于CO_(2)转化制备高附加值化学品和燃料以实现二氧化碳利用及能源储存至关重要。CO_(2)加氢包括甲烷化、逆水煤气变换、甲醇化和CO_(2)直接费托合成等。碳化钼,尤其是其二维材料,由于其低成本和良好的性能而备受关注。在CO_(2)加氢反应中,由于碳的渗入,导致晶格膨胀以及价电子增加,碳化钼基催化剂展现出了类似于贵金属催化剂的性质。碳化钼可以通过程序升温渗碳法、选择性蚀刻法、机械合金合成法、化学气相沉积法、原位热渗碳法以及溶液相合成法等来制备。到目前为止,学者已经对基于碳化钼的材料的CO_(2)转化进行大量研究,这些材料具有良好的CO_(2)转化活性和对目标产物的选择性。碳化钼材料的催化性能可以通过调节碳化钼中的C/Mo比、在碳化钼与负载金属之间建立强的金属-载体相互作用以及调整材料的界面结构来实现。然而,基于碳化钼的热催化CO_(2)转化仍处于初级阶段。本文综述基于碳化钼的热催化CO_(2)加氢制备高附加值化学品和燃料的研究进展,并分析其面临的挑战和机遇。

CO_(2)hydrogenation is critical to producing high-value-added carbon-based chemicals and fuels to achieving both hydrogen energy storage and CO_(2)utilization.Examples of CO_(2)hydrogenation include methanation(Sabatier process)to produce methane,reverse water-gas shift reaction(RWGS)to generate CO,methanol synthesis for the methanol economy,and CO_(2)direct Fischer-Tropsch(CO_(2)-FT)reaction to produce olefins.The precious metal catalysts used in these reactions are efficient but too expensive to be used on a large scale.Further,although some non-precious metal catalysts can be used for these hydrogenation reactions,they suffer from deactivation during long-term processes.Over the past few decades,molybdenum carbides,which are transition metal carbides(TMCs),have attracted significant attention owing to their low cost and similar catalytic performance to precious metal catalysts in CO_(2)hydrogenation reactions.Recently,two-dimensional molybdenum carbide MXenes have shown impressive activity in CO_(2)hydrogenation reactions.Owing to the presence of carbon,the MXene lattice is expanded;this leads to an increase in valence electrons and endows the two-dimensional molybdenum carbidebased catalyst with different properties than metallic Mo.The two-dimensional molybdenum carbide-based materials can be prepared by temperature-programmed carburization,selective etching,mechanical alloying synthesis,chemical vapor deposition,in situ thermal carburization,and solution-phase synthesis methods.Thus far,a host of studies have been performed on CO_(2)conversion with molybdenum carbide-based materials,which show promising activity during CO_(2)conversion and selectivity towards target products.Bothα-MoC1-x andβ-MoCy have shown outstanding thermocatalytic activity,product selectivity,and reaction stability during CO_(2)hydrogenation to CO at 300-600℃.In addition,molybdenum carbide-based materials were also found to be an interesting catalyst for direct CO_(2)Fischer-Tropsch synthesis.The application potential of the molybdenum carbide-based materials could be further tuned by changing the C/Mo ratio in the bulk molybdenum carbide,strengthening the interactions between molybdenum carbide and the supported metal,and tailoring the interface structure of the materials.However,the thermal catalytic CO_(2)conversion based on molybdenum carbide-based materials is still in its infancy.This paper summarizes the progress toward molybdenum carbide catalysis of CO_(2)hydrogenation process for producing high-value-added chemicals and fuels.Furthermore,the challenges and opportunities for molybdenum carbide materials as catalysts for CO_(2)hydrogenation are discussed to provide insights for future development in this emerging field.