Activity-selectivity trends in the electrochemical production of hydrogen peroxide over single site metal-nitrogen-carbon catalysts.

By Yanyan Sun, L. Silvioli, N. R. Sahraie, W. Ju, Jingkun Li, A. Zitolo, Shuang Li, A. Bagger, L. Arnarson, Xingli Wang and 5 more. Journal of the American Chemical Society, 2019

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Nitrogen-doped carbon materials featuring atomically dispersed metal cations (M-N-C) are an emerging family of materials with potential applications for electrocatalysis. The electrocatalytic activity of M-N-C materials toward four-electron oxygen reduction reaction (ORR) to H2O is a mainstream line of research for replacing platinum-group-metal based catalysts at the cathode of fuel cells. However, fundamental and practical aspects of their electrocatalytic activity toward two-electron ORR to H2O2, a future green "dream" process for chemical industry, remained poorly understood. Here we combined computational and experimental efforts to uncover the trends in electrochemical H2O2 production over a series of M-N-C materials (M=Mn, Fe, Co, Ni, and Cu) exclusively comprising atomically dispersed M-Nx sites from molecular first principles to bench-scale electrolyzers operating at industrial cur-rent density. We investigated the effect of the nature of 3d-metal within a series of M-N-C catalysts on electrocatalytic activi-ty/selectivity for ORR (H2O2 and H2O products) and H2O2 reduction reaction (H2O2RR). Co-N-C catalyst was uncovered with out-standing H2O2 productivity considering its high ORR activity, highest H2O2 selectivity, and lowest H2O2RR activity. The activity-selectivity trend over M-N-C materials was further analyzed by density functional theory, providing molecular-scale understandings of experimental volcano trends for four- and two-electron ORR. The predicted binding energy of HO* intermediate over Co-N-C catalysts located near the top of the volcano accounting for favourable two-electron ORR. The industrial H2O2 productivity over Co-N-C catalyst was demonstrated in a micro flow cell, exhibiting unprecedented production rate of more than 4 moles peroxide gcatalyst-1 h-1 at current density of 50 mA cm-2.

Subfields: Electrical and Electronic Engineering, Renewable Energy, Sustainability and the Environment

View Paper: https://www.semanticscholar.org/paper/d96041dba82a09a5eda6aa57fd2c1b5279e2c6b0