Enhanced Electrocatalytic Urea Oxidation Performance of Phosphate-Assisted Bimetallic Nickel-Cobalt Oxalate

Bhandary, Nitik (2025) Enhanced Electrocatalytic Urea Oxidation Performance of Phosphate-Assisted Bimetallic Nickel-Cobalt Oxalate. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Nitik Bhandary (23MP012)) 23MP012_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (3MB)

Abstract

Ni-based materials displayed promising electrocatalytic urea oxidation performance owing to their inherent oxophilicity. Further, the oxalate ligand provides superior structural stability under wide pH conditions and exhibits no catalyst poisoning. Herein, we report phosphate-assisted bimetallic nickel-cobalt oxalate (NiCoOX(T)) via hydrothermal pathway using ammonium nickel phosphate hydrate (NH₄NiPO₄·6H₂O) as the nickel precursor and investigated the alkaline UOR competency. The detailed physical characterizations confirm that NiCoOX(T) exhibits higher geometric performance compared to directly synthesized Ni-Co oxalate (NiCoOX(S)). The NiCoOX(T) achieves a benchmark 10 mA cm² current density at a low applied potential of 1.32 V vs. RHE, and a significantly low Tafel slope of 143 mV dec¹. The morphological analyses reveal that NiCoOX(T) consists of smaller microrods than NiCoOX(s) with abundant active site density. For practical application, the NiCoOX(T)‖Pt/C electrolyzer was constructed, exhibiting a 200 mV reduction in cell potential (1.36 V) for UOR electrolysis compared to conventional water splitting (1.56 V). Further, the electrolyzer demonstrates 40 hours of cyclic stability ( 4 cycles of recyclability) with minimal performance drop, suggesting suitability for real-world application.

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