Ammonia electro-oxidation on nickel hydroxide: phases, pH and poisoning.

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)/γ-NiOOH β-Ni(OH)/β-NiOOH) has never been investigated. Herein, the crystalline β-Ni(OH) and the disordered α-Ni(OH) were synthesized and characterized by XRD, HRSEM, and Raman and FTIR spectroscopies.