Boronization of Nickel Foam for Sustainable Electrochemical Reduction of Nitrate to Ammonia

Abstract

Electrochemical reduction of aqueous nitrates has emerged as a sustainable and practical approach in combining water treatment and ammonia fertilizer synthesis. However, the development of highly integrated catalytic electrodes with consistently high activity from non-noble metals remains a challenging issue despite the potential to greatly decrease costs and promote real-world applications. Here, we report a high-performance electrode with electron-abundant surfaces obtained from direct boronization of nickel foam, rendering a stable ammonia yield rate of 19.2 mg h–1 cm–2 with high Faradaic efficiency of 94% for NO3 –-to-NH3 conversion. The microprocessing lowers the work function and initiates a local electric field for the nickel foam by converting acid-stable surface nickel oxides into dyadic nanosheets composed of metallic nickel and amorphous nickel borates, thus promoting the adsorption and transformation of nitrate anions. Furthermore, the spent electrode enables a rapid and effective regeneration by undergoing another round of boronization, which ensures a long lifetime for the practical application of our electrode design.

Recent Progress and Perspectives on Transition Metal-Based Electrocatalysts for Efficient Nitrate Reduction

“…Carbon material carriers (e.g., activated carbon, carbon cloth, carbon paper, carbon nanofibers, and graphene) also have a large specific surface area, dense pore structure, and good electrical conductivity, which allow smaller sized metal particles to be adequately distributed on the surface of the carriers while enabling rapid electron transfer from the carrier shell thereby activating the catalytic effect of the metal. Nickel foam , and copper foam have excellent porous structures and large specific surface areas while carrying the metal elements themselves; thus, they can be used as self-supporting materials.…”

Cu/NiO nanorods for efficiently promoting the electrochemical nitrate reduction to ammonia

“…In particular, the pollution of nitrate in groundwater can directly or indirectly harm human health. 12,13 In recent years, there have been various methods for treating nitrate pollution in soil and water, such as bacterial denitrification, 14,15 ion reverse osmosis, 16,17 and electrodialysis. 18 However, these methods cannot effectively eliminate nitrate, let alone converting it into valuable chemical products.…”

Crystalline modulation of zirconia for efficient nitrate reduction to ammonia under ambient conditions

“…Transition metals with strong redox properties due to the unsaturated d-electron shells have been widely used for the NITRR. [15][16][17][18][19][20] Since zirconia (ZrO 2 ) is highly chemically stable in acidic or alkaline environments, it can be potentially used as a catalyst, 21 catalyst additive 22 and carrier. 23 For the NITRR, Xia et al reported that Cu-loaded ZrO 2 nanofibers significantly inhibited the competitive hydrogen evolution reaction during nitrate reduction.…”