A Survey of Catalytic Materials for Ammonia Electrooxidation to Nitrite and Nitrate

Johnston, Sam; Cohen, Sam; Nguyen, Cuc; Dinh, Khang Ngoc; Nguyen, Tam D.; Giddey, Sarbjit; Munnings, Christopher; Simonov, Alexandr N.; MacFarlane, Douglas R.

doi:10.1002/cssc.202200614

Cited by 19 publications

(24 citation statements)

References 54 publications

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“…The variation of hydrogen adsorption charge versus N ads surface coverage over time was then quantified because the N ads species would also hinder the hydrogen adsorption on the electrode surface (Figure 5c). The similar trends of the decrease in hydrogen adsorption over the catalyst [55] Copyright 2022, Wiley-VCH. c) CV profiles of activated NiCuFe (a-NiCuFe) electrode and activated NiCu (a-NiCu) electrode.…”

Section: Rotating Disc Electrode Systemmentioning

confidence: 59%

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Green Chemistry: Advanced Electrocatalysts and System Design for Ammonia Oxidation

et al. 2023

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Fossil fuels, including coal, petroleum, and natural gas, are still the main sources of energy supply in the world at present. [1,2] Their nonrenewable nature, however, determines that the total amount of these fossil fuels is limited, thus leading to the potential energy crisis. [3,4] This issue has given a strong impetus to the development of green, safe, and renewable energy supplies, such as wind, solar, and tide energy. [5][6][7][8] Although these novel energy sources are generally sustainable, their direct utilization is extremely difficult. For example, these green energy types, especially solar energy, commonly suffer high fluctuation, thus leading to the misalignment of electricity generation of these energies with the actual demand. [9] Therefore, it is very important to explore and exploit the optimal secondary energy carriers. Among the secondary energy carriers, hydrogen is one of the most economical and eco-friendly carriers due to its zero-carbon emission, abundance, high energy density (120 MJ kg À1 ), etc. [10][11][12] Due to the potential safety hazards in the storage and transportation of hydrogen gas, nevertheless, its practical utilization has great limitations. [13,14] To address these issues, it has been suggested to use methane or ammonia gas as the hydrogen carriers. [15][16][17][18] Methane has a wide range of resources and mature industrial processing technologies. Thermal catalytic decomposition of methane and steam reforming is the most mature technology of hydrogen generation in the industry currently. [19,20] However, the transportation and storage of methane remain problematic owing to its physical characteristics, which are similar to those of hydrogen. As a cost-effective hydrogen carrier, ammonia can turn into a liquid state at room temperature under moderate pressure (%8 bar), much milder than that hydrogen gas (690 bar and 15 °C). [10,21,22] Besides, the utilization of ammonia does not associate with greenhouse gas emissions. Moreover, the energy density of liquid ammonia (11.5 MJ kg À1 ) is also higher than that of liquid hydrogen (8.5 MJ kg À1 ). Moreover, the presence of ammonia can be easily detected even at a very low concentration of 1 ppm, allowing ammonia leaks to be assessed and dealt with in a timely manner. In addition, unlike hydrogen, ammonia is widely used and vastly produced (global production is 176 million tons a year) around the world in the pharmaceutical, fertilizer, and chemical industries. Consequently, the well-established and mature ammonia production-related infrastructure makes ammonia a viable energy source. [23][24][25][26] To utilize ammonia for energy applications, electrochemical ammonia oxidation reaction (AOR) is essential, either for hydrogen production via ammonia splitting or electricity generation via direct ammonia fuel cells (DAFCs), which are highly commercially promising. During operation, DAFCs just produce water and nitrogen gas. [22,[27][28][29] In addition, ammonia fuel cells are also theoretically superior to their hydrogen-based c...

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Section: Rotating Disc Electrode Systemmentioning

confidence: 59%

Section: An Overview Of Aormentioning

confidence: 99%

Green Chemistry: Advanced Electrocatalysts and System Design for Ammonia Oxidation

et al. 2023

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“…This provides strong evidence that nitrite and nitrate are formed from gaseous products (NO and NO 2 ) in the presence of Pt surface oxides. To evaluate nitrite and nitrate production, Johnston et al 32 studied the AOR in Pt/carbon fiber paper (0.1 μmol Pt cm −2 ) using CA and IC and found that nitrate production was 11 times higher than that of nitrite. This is opposite to the trend found in our results.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…OLEMS measurements were performed using an OmniStar Pfeiffer Vacuum mass spectrometer (GSD 301 O1), with simultaneous signal collection of ion fragments (m/z 17, 18,28,30,32,33,43,44,46). Figure S3 IC was used to measure the solution concentrations of AOR products.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Challenges in Electrocatalysis of Ammonia Oxidation on Platinum Surfaces: Discovering Reaction Pathways

2023

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A deep understanding of the ammonia oxidation reaction (AOR) over platinum surfaces may facilitate the use of ammonia as a carbon-free source for energy storage and conversion. Herein, using an unprecedented experimental approach of combining online electrochemical mass spectrometry (OLEMS) and ion chromatography (IC) with high-area Pt/C surfaces, many AOR products were simultaneously detected and the variation in AOR selectivity depending on the surface conditions was demonstrated. In the low-potential region of 0.40−0.82 V, the adsorbed OH − was the dominant oxygenated surface species. The AOR onset potential was 0.40 V, and the surface intermediates were NH x,ads and N 2 H y,ads , which were the main precursors of N 2 , considered a major product. N 2 H 4 , NO, and NH 2 OH were considered minor products in this potential region. In the high-potential region, from 0.82 V, adsorbed O 2− was the main oxygenated surface species, owing to the strong interactions between OH − and oxidized Pt. We found that NO and N 2 O play a key role as reaction intermediates. Another remarkable result is the detection of HN 3 as a gaseous product. NO 2 , N 2 H 4 , and NH 2 OH were considered the minor products. The nitrite and nitrate detected by IC were solution-phase products of the AOR at high potentials. The real-time identification of seven gaseous products, viz., N 2 , NO, N 2 H 4 , NH 2 OH, HN 3 , N 2 O, and NO 2 , and two solution-phase products, NO 2 − and NO 3 − , enabled us to propose AOR mechanistic pathways, opening more possibilities for the electrochemical generation of high-value-added nitrogenated products depending on Pt surface conditions.

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“…Over the past 100 years, it was believed that only precious metals and their alloys can effectively catalyze AO . It was not until the 2000s that non-noble-metal heterogeneous AO catalysts were developed, featuring alloys, hydroxides, and nitrides of Fe, Co, Ni, and Cu. These catalysts have good durability, but their activity is far less than that of noble metal catalysts …”

Section: Artificial Ammonia Oxidationmentioning

confidence: 99%

Electrochemical Ammonia Oxidation with Molecular Catalysts

et al. 2023

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Electrocatalytic ammonia oxidation (AO) provides an attractive route to a carbonneutral fuel economy and the energy-efficient production of value-added feedstocks. The design and study of molecular catalysts can give a deeper mechanistic understanding of AO, which will aid in optimizing catalysts for overpotential, efficiency, and chemoselectivity. This Perspective introduces the topic with biological AO chemistry and then surveys the recent developments of molecular AO electrocatalysts, followed by a discussion of design strategies for new catalysts.

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A Survey of Catalytic Materials for Ammonia Electrooxidation to Nitrite and Nitrate

Cited by 19 publications

References 54 publications

Green Chemistry: Advanced Electrocatalysts and System Design for Ammonia Oxidation

Green Chemistry: Advanced Electrocatalysts and System Design for Ammonia Oxidation

Challenges in Electrocatalysis of Ammonia Oxidation on Platinum Surfaces: Discovering Reaction Pathways

Electrochemical Ammonia Oxidation with Molecular Catalysts

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