Engineering Ni/Ni3N/MoN interface with strain modulation toward sustainable high-current-density alkaline seawater hydrogen production via in situ ammonium formation

Abstract

In recent years, it has been proven that seawater electrolysis is a viable route to hydrogen production. Nevertheless, scaling up is hindered by the sluggish reaction kinetics and inferior durability in the complex ionic environment of seawater. In this work, the hybrid Ni/Ni₃N/MoN on nickel foam (NN/MN/NF) was designed for the hydrogen evolution reaction (HER) in alkaline seawater. For this catalyst, abundant heterogeneous interfaces with tensile strain markedly facilitated electron transport, thereby substantially boosting the reaction kinetics. In an alkaline seawater electrolyte, the catalyst demonstrated exceptional activity, with the HER overpotential as low as 71 mV at a current density of 300 mA cm⁻². Furthermore, the electrocatalyst operated for more than 100 h without severe decay as durability measurements were conducted at 500 mA cm⁻², whereas considerable precipitates coated the NF counterpart after 108 h of long-term testing. The in situ surface-enhanced infrared absorption spectroscopy experimental results demonstrated that NH₄⁺ groups are in situ-generated on the catalyst's surface during seawater electrolysis. These NH₄⁺ groups effectively repel alkaline earth cations in proximity to the electrode surface, thus inhibiting the generation of hydroxide precipitates in the electric double layer. This work provides a novel strategy and inspiration for designing efficient and robust electrocatalysts for hydrogen production from seawater, significantly advancing the research in clean energy systems.