NiP/Fe3P/MoP@NF nanoblocks as a bifunctional electrocatalyst for water splitting in alkaline seawater and urea solution

Abstract

Compared with conventional electrolytic fresh water for hydrogen generation, electrolytic seawater for hydrogen production is more cost-effective, because seawater resources are rich, and fresh water resources are short. However, there are many impurity ions in seawater, especially chloride ions, which have great corrosion on the catalyst, so it is a major factor restricting the development of electrolytic seawater. In this study, a novel NiP/Fe3P/MoP@NF catalyst was made via conventional hydrothermal and phosphating method. Experimental results show that the overpotential of NiP/Fe3P/MoP@NF catalyst in the current density of 10mAcm−2 is just 40mV for hydrogen evolution reaction (HER) and the overpotential of NiP/Fe3P/MoP@NF catalyst in the same condition is 135mV for oxygen evolution reaction (OER) in 1M KOH and seawater solution. In electrolyte solution of 0.5M urea and 1M KOH, the overpotential of NiP/Fe3P/MoP@NF catalyst in the same current density of 10mAcm−2 is 51mV for HER. Furthermore, the whole alkaline seawater splitting requires an applied voltage of 1.66V at current density of 10mAcm−2. Experimental results show that the increased catalytic activity is assigned to the rapid electron transport rate, the exposure of more activity sites, and their synergistic catalysis. The density functional theory (DFT) can show that MoP has the best Gibbs free energy for hydrogen and electrical conductivity compared with NiP and Fe3P, thus enhancing the catalytic performance of NiP/Fe3P/MoP@NF. The paper proposes novel ideas concerning the exploration of catalysts in alkaline seawater and urea solution.