New strategy to improve H2O2 utilization in photocatalytic reaction

Recently, a research team led by Prof. HUANG Weixin from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS) realized the production of oxygenated chemicals from methane and H₂O₂ with oxide semiconductor as photocatalyst, revealed a new strategy for improving H₂O₂ utilization and photocatalytic conversion efficiency from methane to oxygenates, and studied the photocatalytic activity and selectivity by tuning TiO₂ facets. This work was published in Nature Communications.

Methane has been increasingly considered as a possible carbon resource, but it is a major challenge to convert methane to value-added chemicals with both high activity and selectivity.

H₂O₂ is a common oxidant that could photocatalytically convert liquid-phase methane to value-added chemicals. It reacts with photogenerated electrons and produce ·OH radicals or ·OOH radicals, which is an effective activation method. Unfortunately, H₂O₂ is subjected to side reaction with photogenerated holes and tends to converts itself to O₂, reducing its utilization.

In this study, the researchers aerated O₂ into the semiconductor photocatalytic reaction system containing methane and H₂O₂, and found that H₂O₂ utilization was enhanced. They discovered that the adsorption of O₂ onto the surface of TiO₂ inhibited the adsorption of H₂O₂, which suppressed side reactions.

In addition, the researchers observed that photocatalytic activity and selectivity was determined by TiO₂ facets. In virtue of theoretical calculation, they discovered that it was the desorption energy of different products on different TiO₂ facets that accounted for the different catalytic selectivity. For example, CH₃OOH had low desorption energy on TiO₂{101}, thus it was the only liquid-phase product of TiO₂{101}-C₃N₄composite.

This work offered a new strategy for improving H₂O₂ utilization and conversion efficiency in the photocatalytic conversion from methane to oxygenates. It also manifested the role that the catalyst facets played during photocatalytic reactions.