Facile synthesis of Ni-Cu phosphorous as an efficient water oxidation electrocatalyst via electrodeposition

Abstract

Electrochemical water splitting has attracted great attention since it is the most promising strategy for large-scale hydrogen production. Efficient electrolysis is limited due to sluggish kinetics of oxygen evolution reaction (OER), however, as well as high cost of state-of-art precious metals. Hence, numerous researchers endeavored to develop highly active electrocatalyst with low cost. Indebted to this, this study was focused on synthesis of nickel-copper phosphorous electrocatalyst with high OER activity via facile electrodeposition. Optimization of preparation condition confirmed that nickel-copper phosphorous prepared with electrolyte containing 199:1 of Ni2+/Cu2+ ratio exhibited best performance, which even surpasses the OER activity that of NiP, which is already reported as efficient OER catalyst. Suitable Cu addition resulted in lowered Tafel slope and charge transfer resistance compared to NiP. XPS study revealed that Cu addition enhances the role of Ni-P supporting layer, which lies right underneath the OER active, but thermodynamically unstable Ni hydroxide species. Ni spectra showed higher high-valence-state Ni species when Cu was added in the catalyst. The catalyst was electrodeposited with nano-crystalline phase, explained by XRD patterns. According to SEM image, nickel-copper phosphorous has film-like morphology, with uniform element distribution throughout the surface. The catalyst showed excellent robustness up to 18 hrs of OER operation, as well as high Faradaic efficiency over 99%.