Sato Hiromasa, Ishikawa Atsushi, Saito Hikaru, Higashi Taisuke, Takeyasu Kotaro, Sugimoto Toshiki
Department of Materials Molecular Science, Institute for Molecular Science, Okazaki, Aichi, 444-8585, Japan.
The Graduate University for Advanced Studies, SOKENDAI, Hayama, Kanagawa, 240-0193, Japan.
Commun Chem. 2023 Jan 20;6(1):8. doi: 10.1038/s42004-022-00803-3.
On-site and on-demand photocatalytic methane conversion under ambient conditions is one of the urgent global challenges for the sustainable use of ubiquitous methane resources. However, the lack of microscopic knowledge on its reaction mechanism prevents the development of engineering strategies for methane photocatalysis. Combining real-time mass spectrometry and operando infrared absorption spectroscopy with ab initio molecular dynamics simulations, here we report key molecular-level insights into photocatalytic green utilization of methane. Activation of the robust C-H bond of methane is hardly induced by the direct interaction with photogenerated holes trapped at the surface of photocatalyst; instead, the C-H activation is significantly promoted by the photoactivated interfacial water species. The interfacial water hydrates and properly stabilizes hydrocarbon radical intermediates, thereby suppressing their overstabilization. Owing to these water-assisted effects, the photocatalytic conversion rates of methane under wet conditions are dramatically improved by typically more than 30 times at ambient temperatures (300 K) and pressures (1 atm) in comparison to those under dry conditions. This study sheds new light on the role of interfacial water and provides a firm basis for design strategies for non-thermal heterogeneous catalysis of methane under ambient conditions.
在环境条件下实现现场和按需光催化甲烷转化是全球可持续利用无处不在的甲烷资源面临的紧迫挑战之一。然而，对其反应机理缺乏微观认识阻碍了甲烷光催化工程策略的发展。结合实时质谱、原位红外吸收光谱和从头算分子动力学模拟，我们在此报告了对甲烷光催化绿色利用的关键分子水平见解。甲烷中强健的C-H键很难通过与捕获在光催化剂表面的光生空穴直接相互作用而被激活；相反，光活化的界面水物种能显著促进C-H键的活化。界面水使烃基自由基中间体水合并适当稳定，从而抑制它们过度稳定。由于这些水辅助效应，与干燥条件相比，在环境温度（约300K）和压力（约1个大气压）下，潮湿条件下甲烷的光催化转化率显著提高，通常提高30倍以上。这项研究为界面水的作用提供了新的认识，并为环境条件下甲烷非热多相催化的设计策略提供了坚实基础。
