TY - JOUR
T1 - Ammonia electro-oxidation on nickel hydroxide
T2 - phases, pH and poisoning
AU - Offen-Polak, Inbal
AU - Ayali Aviram, Hilla
AU - Hijaze, Adan
AU - Slot, Thierry K.
AU - Eisenberg, David
N1 - Publisher Copyright: © 2025 The Royal Society of Chemistry.
PY - 2024
Y1 - 2024
N2 - Nickel hydroxide is a leading alternative to platinum group metals for electrocatalysis of the ammonia oxidation reaction (AOR), an important process for energy conversion and environmental remediation. Nevertheless, the dependence of AOR electrocatalysis on the different crystalline phases at the electrode surface (α-Ni(OH)2/γ-NiOOH vs. β-Ni(OH)2/β-NiOOH) has never been investigated. Herein, the crystalline β-Ni(OH)2 and the disordered α-Ni(OH)2 were synthesized and characterized by XRD, HRSEM, and Raman and FTIR spectroscopies. The respective electrocatalytic activity of the two phases was analysed at a broad range of ammonia concentrations (0.01-2 M) and pH values (11-13). Both phases electrocatalyze the oxidation of NH3 to N2, as proven by online mass spectrometry, but the α-Ni(OH)2/γ-NiOOH couple is more active. At high ammonia concentrations (>1 M), surface poisoning by adsorbed NH3 prevents access to OH−, leading to less NiOOH formation, lower AOR currents, and suppression of the OER side reaction. The poisoning is strong and irreversible on α-Ni(OH)2, as confirmed by soaking experiments. The difference in ammonia adsorption and electrocatalytic activity between the α-Ni(OH)2 and β-Ni(OH)2 emphasizes the importance of understanding the phase space of nickel hydroxide electrodes when designing low-cost electrocatalysts for the nitrogen cycle.
AB - Nickel hydroxide is a leading alternative to platinum group metals for electrocatalysis of the ammonia oxidation reaction (AOR), an important process for energy conversion and environmental remediation. Nevertheless, the dependence of AOR electrocatalysis on the different crystalline phases at the electrode surface (α-Ni(OH)2/γ-NiOOH vs. β-Ni(OH)2/β-NiOOH) has never been investigated. Herein, the crystalline β-Ni(OH)2 and the disordered α-Ni(OH)2 were synthesized and characterized by XRD, HRSEM, and Raman and FTIR spectroscopies. The respective electrocatalytic activity of the two phases was analysed at a broad range of ammonia concentrations (0.01-2 M) and pH values (11-13). Both phases electrocatalyze the oxidation of NH3 to N2, as proven by online mass spectrometry, but the α-Ni(OH)2/γ-NiOOH couple is more active. At high ammonia concentrations (>1 M), surface poisoning by adsorbed NH3 prevents access to OH−, leading to less NiOOH formation, lower AOR currents, and suppression of the OER side reaction. The poisoning is strong and irreversible on α-Ni(OH)2, as confirmed by soaking experiments. The difference in ammonia adsorption and electrocatalytic activity between the α-Ni(OH)2 and β-Ni(OH)2 emphasizes the importance of understanding the phase space of nickel hydroxide electrodes when designing low-cost electrocatalysts for the nitrogen cycle.
UR - http://www.scopus.com/inward/record.url?scp=85211021939&partnerID=8YFLogxK
U2 - https://doi.org/10.1039/d4cp02950j
DO - https://doi.org/10.1039/d4cp02950j
M3 - مقالة
SN - 1463-9076
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
ER -