Splicing the active phases of copper/cobalt-based catalysts achieves high-rate tandem electroreduction of nitrate to ammonia

Wenhui He, Jian Zhang, Stefan Dieckhöfer, Swapnil Varhade, Ann Cathrin Brix, Anna Lielpetere, Sabine Seisel, João R.C. Junqueira, Wolfgang Schuhmann

Research output: Contribution to journalArticlepeer-review

Abstract

Electrocatalytic recycling of waste nitrate (NO3) to valuable ammonia (NH3) at ambient conditions is a green and appealing alternative to the Haber−Bosch process. However, the reaction requires multi-step electron and proton transfer, making it a grand challenge to drive high-rate NH3 synthesis in an energy-efficient way. Herein, we present a design concept of tandem catalysts, which involves coupling intermediate phases of different transition metals, existing at low applied overpotentials, as cooperative active sites that enable cascade NO3-to-NH3 conversion, in turn avoiding the generally encountered scaling relations. We implement the concept by electrochemical transformation of Cu−Co binary sulfides into potential-dependent core−shell Cu/CuOx and Co/CoO phases. Electrochemical evaluation, kinetic studies, and in−situ Raman spectra reveal that the inner Cu/CuOx phases preferentially catalyze NO3 reduction to NO2, which is rapidly reduced to NH3 at the nearby Co/CoO shell. This unique tandem catalyst system leads to a NO3-to-NH3 Faradaic efficiency of 93.3 ± 2.1% in a wide range of NO3 concentrations at pH 13, a high NH3 yield rate of 1.17 mmol cm−2 h−1 in 0.1 M NO3 at −0.175 V vs. RHE, and a half-cell energy efficiency of ~36%, surpassing most previous reports.

Original languageEnglish
Article number1129
JournalNature Communications
Volume13
Issue number1
DOIs
StatePublished - 1 Dec 2022
Externally publishedYes

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