Quantifying the Contribution of Hot Electrons in Photothermal Catalysis: A Case Study of Ammonia Synthesis over Carbon-supported Ru Catalyst

Photothermal catalysis is one of the most promising green catalytic technologies, while distinguishing the effects of hot electrons and local heating remains challenging. Herein, we reported that the actual reaction temperature of photothermal ammonia synthesis over carbon-supported Ru catalyst can be measured based on Le Chatelier ' s principle, enabling the hot-electron contribution to be quantified. By excluding local heating effects, we established that the activation energy via photothermal catalysis was much lower than that of thermocatalysis (54.9 vs. 126.0 kJ mol(-1)), stemming from hot-electron injection lowering the energy barriers for both N-2 dissociation and intermediates hydrogenation. Furthermore, hot-electron injection acted to suppress carbon support methanation, giving the catalyst outstanding operational stability over 1000 h. This work provides new insights into the hot-electron effects in ammonia synthesis, guiding the design of high-performance photothermal catalysts.

Automated summary

This study measured the actual reaction temperature of photothermal ammonia synthesis over carbon-supported Ru catalyst using Le Chatelier's principle, and found that the activation energy for photothermal catalysis was much lower than thermocatalysis. This was attributed to hot-electron injection reducing the energy barriers for N2 dissociation and intermediates hydrogenation, while also suppressing carbon support methanation. The catalyst exhibited outstanding operational stability over 1000 hours. This work provides new insights into the effects of hot electrons in ammonia synthesis and guides the design of high-performance photothermal catalysts.