What is it about?

Here we report that utilizing sequential proton–electron transfer (SPET) pathways is a viable strategy to enhance the selectivity of electrochemical reactions. The selectivity of an oxo-molybdenum sulfide electrocatalyst toward nitrite reduction to dinitrogen exhibited a volcano-type pH dependence with a maximum at pH 5. The pH-dependent formation of the intermediate species (distorted Mo(V) oxo species) identified using operando electron paramagnetic resonance (EPR) and Raman spectroscopy was in accord with a mathematical prediction that the pKa of the reaction intermediates determines the pH-dependence of the SPET-derived product. By utilizing this acute pH dependence, we achieved a Faradaic efficiency of 13.5% for nitrite reduction to dinitrogen, which is the highest value reported to date under neutral conditions.

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Why is it important?

The development of denitrification catalysts which can reduce nitrate and nitrite to dinitrogen is critical for sustaining the nitrogen cycle. However, regulating the selectivity has proven to be a challenge, due to the difficulty of controlling complex multielectron/proton reactions.

Perspectives

We anticipate that utilization of SPET pathways will become an important concept for electrocatalyst design, particularly for systems with many competing reaction pathways such as CO2 reduction.

Dr. Daoping He
Shanghai Jiao Tong University

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This page is a summary of: Selective Electrocatalytic Reduction of Nitrite to Dinitrogen Based on Decoupled Proton–Electron Transfer, Journal of the American Chemical Society, February 2018, American Chemical Society (ACS), DOI: 10.1021/jacs.7b12774.
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