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 H 2 O 2 with oxide semiconductor as photocatalyst, revealed a new strategy for improving H 2 O 2 utilization and photocatalytic conversion efficiency from methane to oxygenates, and studied the photocatalytic activity and selectivity by tuning TiO 2 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.
H 2 O 2 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, H 2 O 2 is subjected to side reaction with photogenerated holes and tends to converts itself to O 2 , reducing its utilization.
In this study, the researchers aerated O 2 into the semiconductor photocatalytic reaction system containing methane and H 2 O 2 , and found that H 2 O 2 utilization was enhanced. They discovered that the adsorption of O 2 onto the surface of TiO 2 inhibited the adsorption of H 2 O 2 , which suppressed side reactions.
In addition, the researchers observed that photocatalytic activity and selectivity was determined by TiO 2 facets. In virtue of theoretical calculation, they discovered that it was the desorption energy of different products on different TiO 2 facets that accounted for the different catalytic selectivity. For example, CH 3 OOH had low desorption energy on TiO 2 {101}, thus it was the only liquid-phase product of TiO 2 {101}-C 3 N 4 composite.
This work offered a new strategy for improving H 2 O 2 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.
Nature Communications
Molecular oxygen enhances H2O2 utilization for the photocatalytic conversion of methane to liquid-phase oxygenates
5-Nov-2022