Water enables mild oxidation of methane to methanol on gold single-atom catalysts

As a 100% atom-economy process, direct oxidation of methane into methanol remains as a grand challenge due to the dilemma between activation of methane and over-oxidation of methanol. Here, we report that water enabled mild oxidation of methane into methanol with >99% selectivity over Au single atoms on black phosphorus (Au-1/BP) nanosheets under light irradiation. The mass activity of Au-1/BP nanosheets reached 113.5 mu mol g(catal)(-1) in water pressured with 33bar of mixed gas (CH4:O-2=10:1) at 90 degrees C under light irradiation (1.2W), while the activation energy was 43.4kJmol(-1). Mechanistic studies revealed that water assisted the activation of O-2 to generate reactive hydroxyl groups and center dot OH radicals under light irradiation. Hydroxyl groups reacted with methane at Au single atoms to form water and CH3* species, followed by oxidation of CH3* via center dot OH radicals into methanol. Considering the recycling of water during the whole process, we can also regard water as a catalyst.

Automated summary

This study demonstrates that water under light irradiation facilitates high-selective oxidation of methane to methanol by Au single atom catalysts, while also proving that water can be regarded as a catalyst due to its recycling during the entire process.