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

Abstract

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 (Au1/BP) nanosheets under light irradiation. The mass activity of Au1/BP nanosheets reached 113.5 μmol gcatal−1 in water pressured with 33 bar of mixed gas (CH4:O2 = 10:1) at 90 °C under light irradiation (1.2 W), while the activation energy was 43.4 kJ mol−1. Mechanistic studies revealed that water assisted the activation of O2 to generate reactive hydroxyl groups and •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 •OH radicals into methanol. Considering the recycling of water during the whole process, we can also regard water as a catalyst.

Understanding the water molecule effect in metal-free B-based electrocatalysts for electrochemical CO2 reduction

“…53,54 The mechanism of the photocatalytic conversion of CH 4 to CH 3 OH was explored in the presence of water, and the results showed that water can be used as a catalyst to assist in O 2 activation. 55 Zhou et al 56 introduced 36 water molecules and a constant potential correction to construct a real electrochemical environment, which emphasized the importance of hydrogen bond networks for stabilizing reaction intermediates. Wang et al 57 reported the basic mechanism of the interaction between liquid water as a hydrogen source on a metal-free carbon nitride catalyst and oxygen, as well as the reaction mechanism of H 2 O 2 synthesis.…”

Single metal atoms catalysts—Promising candidates for next generation energy storage and conversion devices

“…One of the main challenges for the preparation of SMACs is the high tendency to agglomerate into clusters or nanoparticles with the increment of mass loading. In order to solve this issue, the introduction of uniformly distributed coordination sites, such as N, 46,149,[213][214][215][216][217][218][219] O, [220][221][222][223][224][225] S, 47,[226][227][228][229][230] P, 48,231 or their combinations, [232][233][234][235][236] is a widely-recognized strategy to attract and fix metal SAs by intensifying the metalsupport interaction. Differing from defect anchoring, coordination attraction does not necessarily need defects.…”

Atomically Surficial Modulation in Two-Dimensional Semiconductor Nanocrystals for Selective Photocatalytic Reactions

“…Hence, the single-atom modifications could be applied to regulate the dynamics of photogenerated charge transfer by shortening the charge migration distances and endowing strong interactions between metals and carriers ( Gao et al, 2020 ). For example, the Zeng and Li group designed the single-atom Au-modified black phosphorus (Au 1 /BP) nanosheet catalyst for the selective oxidation process of methane to methanol ( Luo et al, 2021 ). Under light irradiation, 1 O 2 generated by Au 1 /BP could react with water, forming adsorbed P-OH and P-OOH.…”