Metallated Graphynes as Efficient Single-Atom Electrocatalysts for Nitric Oxide Reduction to Ammonia

Abstract

Direct electrochemical ammonia synthesis from nitric oxide is regarded as an attractive strategy to degrade NO contaminants into valuable NH3, but the scarcity of high-efficiency and durable electrocatalysts to facilitate such a process impedes its applications. The emerging transition metal 1,3,5-triethynylbenzene frameworks (TM-TEB), combining the superiorities of single-atom metal centers and graphynes, offer attractive possibilities in electrochemical catalysis. This work comprehensively studies the TM-TEB systems (for TM from the first three d-block series) and explores their potential applications as electrocatalysts for the NO reduction reaction (NORR) to value-added NH3. By developing rational strategies, the systems with TM = Cr, Pd, and Pt are successfully screened out as the NORR-to-NH3 electrocatalysts with superiority catalytic activity. With further consideration of the selectivity, Cr-TEB is identified as a promising candidate with high catalytic activity and outstanding selectivity. Interestingly, both the ΔG*NO and integrated crystal orbital Hamilton population (ICOHP) of TM-NO or N–O could be suitable descriptors to demonstrate the catalytic activity of the NORR to NH3. This work has fundamental scientific implications for understanding the TM-TEB systems and demonstrates their great potential as the electrocatalysts for the NORR to NH3, which will motivate further exploration of the applications of TM-TEB in catalysis.