Identifying the active site of Cu/Cu2O for electrocatalytic nitrate reduction reaction to ammonia

Author(s):Show less -

Costa, Gabriel F. ; Winkler, Manuel ; Mariano, Thiago ; Pinto, Maria R. ; Messias, Igor ; Souza, Joao B. ; Neckel, Itamar T. ; Santos, Maria F. C. ; Tormena, Claudio F. ; Singh, Nirala ; Nagao, Raphael

• Document type: Journal article
• Source: CHEM CATALYSIS; v. 4, n. 1, p. 19-pg., 2024-01-18.

Abstract

Copper oxide -derived electrocatalysts are reported to have high activity and selectivity for nitrate electrochemical reduction reaction (NO3RR) to ammonia. However, the cause underlying their enhanced NH3 formation remains unclear. We measure the NO3RR activity of differently pre -reduced Cu/Cu2O catalysts and compare them to metallic Cu to identify the active site for NO3RR to ammonia in sodium sulfate electrolyte. Using unbuffered electrolyte, catalyst kinetic performance is similar to the alkaline one (pH 12) due to pH increases during NO3RR. Higher pH values improve catalyst performance for NO3RR to NH3 compared to electrolyte buffered at pH 5.8. Using in situ spectroscopies, we detect that Cu2O reduces at - 0.6 V vs. standard hydrogen electrode (SHE) and detect hydroxylamine, a NO3RR intermediate, from -0.7 V to -1.0 V vs. SHE. We propose that oxygen vacancies promote NO3RR to ammonia from - 0.6 to -0.77 V vs. SHE, while copper is the active site at -1.1 V vs. SHE. (AU)

• FAPESP's process: 19/18847-6 - Ammonia electrochemical synthesis from nitrate reduction at metal oxides: an in operando investigation
• Grantee: Gabriel Floriano Costa
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• FAPESP's process: 21/08868-6 - Tandem dissipative electrodes applied in the reduction of carbon dioxide to the formation of C2+ products
• Grantee: Raphael Nagao de Sousa
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Regular Program Grants
• FAPESP's process: 19/08244-2 - Synthesis of nanowires for application in the reduction reaction of carbon dioxide
• Grantee: Maria Rodrigues Pinto
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 23/02841-4 - Co3O4/CuO/Cu electrodes for nitrate electroreduction
• Grantee: Raphael Nagao de Sousa
• Support Opportunities: Regular Research Grants
• FAPESP's process: 22/14169-6 - Electrocatalytic synthesis of ammonia from nitrate reduction: the role of copper and its oxides as efficient catalysts
• Grantee: Raphael Nagao de Sousa
• Support Opportunities: Regular Research Grants
• FAPESP's process: 22/01799-1 - Ammonia electrosynthesis from nitrate reduction: flow cell and in-situ Raman spectroscopic studies
• Grantee: Gabriel Floriano Costa
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate (Direct)
• FAPESP's process: 17/11986-5 - Generation and storage of New Energy: bringing technological development for the country
• Grantee: Ana Flávia Nogueira
• Support Opportunities: Research Grants - Research Centers in Engineering Program