Iron and phosphorus dual-doped NiMoO4 with nanorod structure as efficient oxygen evolution catalyst in alkaline seawater

Abstract

Hydrogen production by electrolysis of seawater is more in line with the new era of green chemistry than electrolysis of freshwater, but the high cost and the accompanying chlorine evolution hinder the development of the process. In this study, the growth of transition metal elements Fe as well as P double-doped NiMoO4 with nanorod-like nanostructures on Ni foam (Fe/P–NiMoO4@NF) is feasible. The optimized Fe/P–NiMoO4@NF material exposes more active sites, which exhibits excellent oxygen evolution reaction (OER) activity in alkaline seawater. At a current density of 10 mA cm−2, the operating potential is only 1.35 V and operating potential of 1.54 V at 100 mA cm−2 is obtained with Tafel slopes as small as 13.16 mV dec−1. The enhanced activity is attributed to the exposure of more active sites and faster charge transfer due to double doping of Fe and P. And the catalyst exhibited relatively good durability, which could be maintained at 50 mA cm−2 for 24 h at a constant voltage of 1.60 V without IR-compensation. The experiment result shows that the doped P smoothly covers on the surface the catalyst, making the surface metal compound on the nickel foam is resistant to seawater corrosion. Density Functional Theory (DFT) shows that double doping of Fe and P can increase the electron transfer rate and enhance the adsorption energy of water. This work provides a new and simple double doping strategy for the development of high-performance catalysts with controllable morphology for seawater splitting.