基于金属氧化物的光催化甲烷转化:原理、进展与挑战

Photocatalytic methane conversion over metal oxides:Fundamentals,achievements,and challenges

随着可燃冰和页岩气开采技术的迅速发展,甲烷的储量逐年增加.因此,甲烷不仅被视为一种清洁能源,同时也被认为是一种可用于生产高附加值化工产品的碳原料.然而,由于甲烷分子具有十分稳定的成键结构,所以传统的甲烷转化技术(尤其是甲烷水汽重整反应)通常需要大量的能量输入.针对这一问题,光催化技术可以利用具有高能量的光生载流子来打破甲烷转化的热力学势垒,被认为是在温和条件下实现甲烷转化的一种非常具有前景的途径.在光催化甲烷转化领域,金属氧化物基光催化剂已经得到了广泛的研究,这主要归因于它们的强氧化能力.在本文中,我们首先基于光催化甲烷转化反应的基本原理对金属氧化物在该反应中所具备的优势进行了讨论.随后,我们回顾了近年来金属氧化物基光催化剂在目前各类甲烷转化反应中的研究进展,包括甲烷完全氧化(TOM)、甲烷部分氧化(POM)、甲烷干重整(DRM)、甲烷无氧偶联(NOCM)以及晶格氧辅助的甲烷偶联(LOCM)等几类反应.最后,我们对基于金属氧化物的光催化甲烷转化技术所面临的挑战与机遇进行了展望.

With the rapid development of combustible ice and shale gas mining technology,the reserve of methane(CH4)has been growing abundant.Therefore,there is a paradigm shift,where CH4 is not seen only as a hydrocarbon fuel,but also as carbon feedstocks for synthesizing various value-added chemicals.However,the conventional CH4 conversion technology,especially steam reforming of methane,normally requires extensive energy input due to the extremely stable bonding of CH4.To this end,photocatalysis,which can break the thermodynamic barrier of CH4 conversion,has been known as a promising candidate for reaching large-scale CH4 conversion under ambient condition.In the photocatalytic CH4 conversion researches,metal oxides have been extensively investigated mainly due to their high oxidation capability.In this review,a discussion is first given on the fundamentals of CH4 conversion and the advantages of metal oxides in such a reaction.Then the development of metal oxides-based photocatalysts in various CH4 conversion reactions is reviewed,including total oxidation of methane(TOM),partial oxidation of methane(POM),dry-reforming of methane(DRM),non-oxidative coupling of methane(NOCM),lattice oxygen mediated oxidative coupling of methane(LOCM)and so on.Finally,the opportunities of metal oxides-based photocatalytic CH4 conversion along with the challenges are summarized.