Improving nitrate-to-ammonia conversion efficiency on electrodeposited nickel phosphide via surface δ-FeOOH modification

Author(s)

Silva, Anelisse B. ; Reis, Eduardo A. ; Hu, Jiajun ; Albero, Josep ; Ribeiro, Caue ; Mascaro, Lucia H. ; Garcia, Hermenegildo

• Document type: Journal article
• Source: JOURNAL OF MATERIALS CHEMISTRY A; v. 13, n. 6, p. 11-pg., 2025-01-02.

Abstract

Electrocatalytic nitrate reduction to ammonia is an appealing and promising approach for recovering industry and agricultural wastewater. However, there is a lack of efficient electrocatalysts for NO3- conversion at low overpotentials and a range of nitrate concentrations, which could enable nitrogen recovery from various wastewater streams. Here, we report an affordable and efficient electrodeposited amorphous-Ni3P electrode modified with delta-FeOOH, forming a heterojunction catalyst that efficiently converts nitrate into ammonia. The optimum heterojunction performance achieved a high faradaic efficiency of 98% +/- 0.72 at -0.3 V vs. RHE with an NH3 production yield of 8.49 mg h-1 cm-2, ranking Ni3P/delta-FeOOH among the most active electrocatalysts so far reported for this process. Ni3P/delta-FeOOH showed good stability using ethyl cellulose as a green and fluoride-free binder without losing the superficial modification. Mechanistic studies by in situ Raman spectroscopy show that the role of delta-FeOOH is the stabilisation of the NOx intermediates. At the same time, Ni3P provides *H species available for NOx reduction, thus resulting in highly selective NO3 hydrogenation. In contrast, in the absence of delta-FeOOH, Ni3P exhibits significantly lower NH3 faradaic efficiency due to simultaneous H2 evolution. Therefore, the present results show the synergistic effect between delta-FeOOH and Ni3P in the electrocatalytic nitrate reduction, with delta-FeOOH playing a crucial role in stabilising the reaction intermediates and enhancing the ammonia selectivity. (AU)

• FAPESP's process: 18/01258-5 - Novel chemical catalytic and photocatalytic processes for the direct conversion of methane and CO2 to products
• Grantee: José Maria Correa Bueno
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 22/15742-1 - New approach for Haber-Bosch process and urea synthesis using coupled electrochemical devices
• Grantee: Anelisse Brunca da Silva
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• 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
• FAPESP's process: 20/11756-2 - Synthesis, characterization, and application of metal phosphide films for CO2 reduction
• Grantee: Anelisse Brunca da Silva
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 21/12394-0 - Sustainable synthetic methods employing catalysis, benign solvents, safer reagents, and bio-renewable feedstock
• Grantee: Arlene Gonçalves Corrêa
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 13/07296-2 - CDMF - Center for the Development of Functional Materials
• Grantee: Elson Longo da Silva
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC