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Explora: Environment
and Resource Electrocatalyst for ammonia oxidation reaction

fuel cells produces only water as a byproduct, making it an using scanning electron microscopy (SEM; ZEISS 300,
extremely clean fuel. HITACHI, Japan) and X-ray photoelectron spectroscopy
Considerable research efforts have focused on (XPS; ESCALAB 250XI, Thermofisher, USA).
electrocatalysts for the ammonia oxidation reaction 2. Methodology
(AOR). Among noble metals, platinum (Pt) showed the
best electrocatalytic activity compared to others. Various 2.1. The synthesis of nickel–cobalt layered double
morphologies of pure Pt, including cubic Pt, sheet-like Pt, hydroxide/platinum composite
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and flower-like Pt, have been reported as catalysts for the 2.1.1. Pre-treatment of nickel foam
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electrochemical AOR. These different morphologies can
be achieved by controlling the electrodeposition potentials The NF was first cut into thin sheets measuring 10 mm ×
and using surfactants. In addition, to further improve AOR 25 mm × 1 mm. The sheets were then placed into a 50 mL
activity, research has extended to certain Pt-based binary beaker and immersed in 3 mol/L hydrochloric acid for
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and ternary electrocatalysts. Vooys et al. established the 10 min. Next, the NF was transferred to ethanol (analytical
nitrogen adsorption strength trend as follows: Ruthenium reagent grade; Tianli Chemical Reagent Company, China)
> rhodium > palladium > iridium > Pt >> gold, silver, and and sonicated for 10 min. Finally, the NF was washed
copper. Therefore, Pt-based alloys, including Pt-nickel with deionized water and dried in an oven (Shangcheng
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(Ni), Pt-iridium, and Pt-gold, have been synthesized, Instrument Manufacturing Company, China) at 50°C for
showing superior electrocatalyst performance compared to later use. The resulting sample is referred to as NF.
pure Pt. In addition, certain oxides, such as yttrium oxide, 2.1.2. Preparation of nickel–cobalt layered double
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stannic oxide, and cerium oxide, have also been used to hydroxide
modify Pt. For example, cerium oxide-modified Pt showed
better AOR performance, including lower onset potential First, 0.571 g of Ni(II) chloride hexahydrate (analytical
and higher oxidation peak current, compared to pure Pt. reagent grade; Shanghai Macklin Biochemical Co.,
Ltd. China) and 0.195 g of Co(II)chloride hexahydrate
In regard to transition metals and their oxides/ (analytical reagent grade: Shanghai Macklin Biochemical
oxyhydroxides, Ni has been regarded as a promising Co., Ltd. China) were added into 50 mL of deionized water
candidate for AOR electrocatalysts. However, challenges and stirred to form a homogeneous solution. Subsequently,
remain, such as the compromised long-term stability 0.30 g of urea (analytical reagent grade; Shanghai
of Ni due to corrosion during ammonia electrolysis. To Macklin Biochemical Co., Ltd. China) was added to the
overcome these issues, various Ni-based materials have aforementioned mixed solution, followed by magnetic
been developed, including Ni–copper alloys, copper stirring for an hour to ensure complete homogenization.
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oxide/Ni hydroxide, Ni–copper oxyhydroxide, Ni– The resultant mixture and a cleaned NF substrate were
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copper–iron oxyhydroxide, and Ni–cobalt (Co) layered transferred into a 100 mL teflon-lined stainless-steel
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double hydroxides. These materials aim to control the autoclave (Wanruigude Company, China), which was then
electron structure and the adsorption of ammonia. For sealed and maintained at 120°C for 12 h in an electric
example, Ren et al. synthesized copper oxide/Ni through oven (Shangcheng Instrument Manufacturing Company,
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a one-step replacement reaction and used charge density China). After naturally cooling to room temperature, the
difference and Mulliken charge analyses to explain the obtained sample was collected, rinsed, and denoted as
enhanced electrocatalytic performance. Wang et al. NiCo-LDH.
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developed a boron-modified Ni–iron layered double
hydroxide (NiFe-LDH) supported on Ni foam (NF), where 2.1.3. Preparation of platinum–(nickel–cobalt layered
boron nanoclusters served as charge bridges to regulate double hydroxide)
electron redistribution in NiFe-LDH and expose more Nickel–cobalt layered double hydroxide was placed into
active metal sites. 21 4 mL centrifuge tubes. Then, 150 μL, 300 μL, 450 μL,
In this work, to fabricate a high-performance and 600 μL of H PtCl ·6H O (0.1 mol/L) (analytical
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electrocatalyst for AOR, NiCo-LDH nanowires were reagent grade; Shanghai Macklin Biochemical Co., Ltd.
first electrodeposited onto NF, followed by the growth China) were added into the centrifuge tubes along with
of Pt nanoparticles through a galvanic replacement 1,350 μL, 1,200 μL, 1,050 μL, and 900 μL of deionized
reaction. The ratio of chloroplatinic acid hexahydrate water, respectively, to obtain a solution with a volume of
(H PtCl ∙6H O), reaction time, and reaction temperature 1,500 μL. The mixtures were placed in a water bath at 20°C
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were systematically controlled, and the resulting samples for 8 h. The obtained Pt-(NiCo-LDH) samples were labeled
were characterized. In addition, the samples were analyzed as Pt-(NiCo-LDH)-X (X = 1, 2, 3, 4). Under the optimal
Volume 2 Issue 3 (2025) 2 doi: 10.36922/EER025170033