Ni(II)/Ni(III) redox couple endows Ni foam-supported Ni2P with excellent capability for direct ammonia oxidation

Wang, Renyu; Liu, Huijuan; Zhang, Kai; Zhang, Gong; Lan, Huachun; Qu, Jiuhui

doi:10.1016/j.cej.2020.126795

Cited by 90 publications

(39 citation statements)

References 59 publications

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“…Nitrate (NO 3 – ) is the major byproduct at lower pH, and only a small amount of nitrite (NO 2 – ) is produced due to the strong oxidative capacity of the electro-oxidation system. The NO 2 – and NO 3 – might be formed during the oxygen-transfer reaction which pass oxygen atoms to the ammonia molecule. , NO 3 – at pH = 12 is relatively higher than pH = 11 and pH = 13. When pH = 13, as shown in Figure S4d, the reduction of NO 3 – was enhanced compared to pH = 12 (Figure S4a).…”

Section: Resultsmentioning

confidence: 98%

“…The selective conversion of ammonia to nitrogen at high-valence metal sites without formation of intermediates would be a green and energy-efficient strategy. Previous reports based on electrocatalytic ammonia oxidation via three-electron transfer showed relatively high byproduct yield at medium-concentration ammonia (∼50%). , Achieving the direct transformation from NH 3 to N 2 is of paramount importance for electrode and reactor design.…”

Section: Introductionmentioning

confidence: 99%

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Optimization of a Hierarchical Porous-Structured Reactor to Mitigate Mass Transport Limitations for Efficient Electrocatalytic Ammonia Oxidation through a Three-Electron-Transfer Pathway

Liu

Zhang

Lan

et al. 2021

Environ. Sci. Technol.

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Regulation of fast three-electron-transfer processes for electrocatalytic oxidation of ammonia to nitrogen by achieving efficient generation and utilization of active sites is the optimal strategy in ammonia-containing wastewater treatment. However, the limited number of accessible active sites and sluggish interfacial mass transfer are two main bottlenecks restricting conventional ammonia oxidation configurations. Herein, we develop a macroporous Ni foam electrode integrated with vertically aligned two-dimensional mesoporous Ni2P nanosheets to create sufficient exposure of active centers. A novel ammonia oxidation reactor with the developed hierarchical porous-structured electrodes was assembled to construct an intensified microfluidic process with flow-through operation to mitigate macroscopic mass transport limitations. The confined microreaction space in the hierarchical porous reactor further promotes spontaneous nanoscale diffusion/convection of the target contaminant to high-valence Ni sites and enhances the microscopic mass transfer. The combined results of electrochemical measurements and in situ Raman spectra showed that the ammonia degradation mechanism results from direct oxidation by the high-valence Ni, significantly different from the conventional indirect active-chlorine-species-mediated oxidation. The optimized reactor achieves high-efficiency three-electron-transfer ammonia conversion with an ammonia removal efficiency of ∼70% from an initial concentration of ∼1400 mg/L and byproduct production of ∼4%, significantly superior to a conversion unit comprising a featureless Ni-based electrode in the immersed configuration, which had >50% byproduct yield. 20 days of continuous operation under variable conditions achieved >90% ammonia degradation performance and an energy consumption of 25.42 kW h kg–1 N (1 order of magnitude lower than the active-chlorine-mediated process), showing the potential of the reactor in medium-concentration ammonia-containing wastewater treatment.

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Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Optimization of a Hierarchical Porous-Structured Reactor to Mitigate Mass Transport Limitations for Efficient Electrocatalytic Ammonia Oxidation through a Three-Electron-Transfer Pathway

Liu

Zhang

Lan

et al. 2021

Environ. Sci. Technol.

Self Cite

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“…Previous work reported that the Ni 2+ /Ni 3+ redox couple acts as the active sites in the ammonia oxidation process. [ 24 ] Therefore, modification of the electronic structure of Ni by annealing in Ar promotes the AOR activity.…”

Section: Resultsmentioning

confidence: 99%

“…As a typical non‐noble catalyst, Ni‐based alloys and hydroxides have been extensively studied due to their highly electrochemical activity, outstanding electrical properties, and good chemical compatibility with other components. [ 24 , 25 , 26 ] In our previous work, we prepared NiCu bimetallic catalyst by direct electrochemical co‐deposition. [ 12 ] Compared with Ni or Cu metal alone, the NiCu bimetal showed excellent electrocatalytic activity and stability toward AOR.…”

Section: Introductionmentioning

confidence: 99%

An Efficient Symmetric Electrolyzer Based On Bifunctional Perovskite Catalyst for Ammonia Electrolysis

Zhang

Duan

et al. 2021

Advanced Science

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Ammonia is a natural pollutant in wastewater and removal technique such as ammonia electro-oxidation is of paramount importance. The development of highly efficient and low-costing electrocatalysts for the ammonia oxidation reaction (AOR) and hydrogen evolution reaction (HER) associated with ammonia removal is subsequently crucial. In this study, for the first time, the authors demonstrate that a perovskite oxide LaNi 0.5 Cu 0.5 O 3-𝜹 after being annealed in Ar (LNCO55-Ar), is an excellent non-noble bifunctional catalyst towards both AOR and HER, making it suitable as a symmetric ammonia electrolyser (SAE) in alkaline medium. In contrast, the LNCO55 sample fired in air (LNCO55-Air) is inactive towards AOR and shows very poor HER activity. Through combined experimental results and theoretical calculations, it is found that the superior AOR and HER activities are attributed to the increased active sites, the introduction of oxygen vacancies, the synergistic effect of B-site cations and the different active sites in LNCO55-Ar. At 1.23 V, the assembled SAE demonstrates ≈100% removal efficiency in 2210 ppm ammonia solution and >70% in real landfill leachate. This work opens the door for developments towards bifunctional catalysts, and also takes a profound step towards the development of low-costing and simple device configuration for ammonia electrolysers.

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“…This unique three-dimensional structure benefits significantly from the use of noble metals. As a result, Ni foams with a particular architecture and excellent conductivity have been successively used as supports for the preparation of catalysts for various electrochemical reactions, such as hydrogen evolution [45], water splitting in alkaline media [46], direct ammonia oxidation [47], methanol oxidation [48], ethanol oxidation [49], sodium borohydride hydrolysis [50], borohydride oxidation [51], hydrazine oxidation [52], and urea oxidation [53]. However, there are no reports of Ni foam as a support for FA oxidation.…”

Section: Introductionmentioning

confidence: 99%

An Enhanced Oxidation of Formate on PtNi/Ni Foam Catalyst in an Alkaline Medium

et al. 2022

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In this study, a platinum-coated Ni foam catalyst (denoted PtNi/Ni foam) was investigated for the oxidation of the formate reaction (FOR) in an alkaline medium. The catalyst was fabricated via a two-step procedure, which involved an electroless deposition of the Ni layer using sodium hypophosphite as a reducing agent and the subsequent electrodeposition of the platinum layer. The PtNi/Ni foam catalyst demonstrated enhanced electrocatalytic activity for the FOR in an alkaline medium compared to the Ni/Ni foam catalyst and pure Pt electrode. Moreover, the PtNi/Ni foam catalyst promoted the FOR at more negative potentials than the Pt electrode. This contributed to a significant negative shift in the onset potential, indicating the high activity of the catalyst. Notably, in alkaline media with the PtNi/Ni foam catalyst, the FOR proceeds via a direct pathway mechanism without significant accumulation of poisonous carbonaceous species on the PtNi/Ni foam catalyst.

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Ni(II)/Ni(III) redox couple endows Ni foam-supported Ni2P with excellent capability for direct ammonia oxidation

Cited by 90 publications

References 59 publications

Optimization of a Hierarchical Porous-Structured Reactor to Mitigate Mass Transport Limitations for Efficient Electrocatalytic Ammonia Oxidation through a Three-Electron-Transfer Pathway

Optimization of a Hierarchical Porous-Structured Reactor to Mitigate Mass Transport Limitations for Efficient Electrocatalytic Ammonia Oxidation through a Three-Electron-Transfer Pathway

An Efficient Symmetric Electrolyzer Based On Bifunctional Perovskite Catalyst for Ammonia Electrolysis

An Enhanced Oxidation of Formate on PtNi/Ni Foam Catalyst in an Alkaline Medium

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