Eletrodeposição de liga à base de Ni, Co e P para aplicação na eletrólise da água

Abstract

This work investigates a NiCoP catalyst obtained by electrodeposition for alkaline water electrolysis. Since the electrodeposition conditions directly influence the morphology, composition, and electrocatalytic activity of the film, a central composite design was employed to optimize the catalyst electrodeposition conditions. The studied variables were the concentrations of [NiSO4], [CoSO4], and [NaH2PO2], as well as the applied current density (jd), while the responses of the experimental design were the overpotentials at 10 and 100 mA cm⁻2 (η10 and η100, respectively) for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The obtained films exhibited limited activity toward the OER, with a maximum overpotential reduction lower than 50 mV compared to the stainless steel substrate. In contrast, promising results were observed for the HER, with a coefficient of determination (R2) of 80.2 % for η10, where the NiSO4 concentration and current density were identified as significant effects at a 95 % confidence level. Although [CoSO4] and [NaH2PO2] were not statistically significant, the complete removal of these salts severely compromised the catalytic performance. However, the desirability study indicated that their concentrations can be reduced by up to 50 % and 80 %, respectively, without significant loss in HER activity or catalyst composition. In the second stage, the optimized electrodeposition condition for the NiCoP catalyst was evaluated in an anion exchange membrane water electrolyzer (AEMWE), using Ni3Fe-LDH as the anode in 1.0 mol L⁻1 KOH solution at Forschungszentrum Jülich, Germany. The polarization curves recorded for this system before and after 240h of operation at 1.0 A cm⁻2 showed similar profiles, reaching 1.0 A cm⁻2 at 2.00 V. Overall, this work demonstrates the potential of electrodeposited NiCoP, a simple and low-cost synthesis method, as a catalyst with competitive electrochemical performance for the HER in AEMWE systems.