Exploring the role of different morphologies of β–Ni(OH)2 for electrocatalytic urea oxidation and the effects of electrochemically active surface area

Abstract

Ni(OH)2, as a multifunctional material, has found its applications in a great number of research areas. In particular, it is an efficient catalyst for urea oxidation reaction (UOR), which is an important alternative to oxygen evolution reaction in electrocatalytic water splitting. This work investigates the effect of materials morphology on the electrocatalytic UOR performance of β–Ni(OH)2, as well as the importance of characterising the catalysts’ surface by electrochemical active surface area. Three different morphologies (nanoflowers, nanocubes, and nanosheets) were prepared via a simple hydrothermal approach. The morphology and structure of the as-prepared samples were carefully examined by scanning electron microscopy, transmission electron microscopy, and powder X-ray diffraction. The UOR performance of β–Ni(OH)2 was evaluated by means of cyclic voltammetry, linear sweep voltammetry, Tafel analysis, and electrochemical surface area. Nanosheet Ni(OH)2 electrocatalyst exhibits higher current density responses (28.3 mA cm−2 ECSA at 1.6 V vs. RHE) and a lower slope in the Tafel plot (72.6 mV dec-1). Consequently, due to the exposure of more active sites to the reactants, the Ni(OH)2 electrode with nanosheet morphology displayed higher electrocatalytic performance during UOR compared to the nanoflower and nanocube samples.

Keywords

• Urea Oxidation Reaction
• Ni(OH)2
• Electrocatalysis
• Morphology
• Active site