Self-supported NiTe@NiMo electrodes enabling efficient sulfion oxidation reaction toward energy-saving and chlorine-free hybrid seawater electrolysis at high current densities†

Abstract

The sulfion oxidation reaction (SOR) assisted seawater electrolysis has been proposed to be a potentially cost-effective approach to hydrogen production because SOR happens at an anodic potential significantly lower than that of the energy-demanding oxygen evolution reaction (OER). However, the key to unleash full potential of SOR for practical seawater electrolysis is to develop highly efficient and stable electrocatalysts able to sustain in harsh seawater environment at high current densities. Herein, we report the fabrication of nickel foam supported nickel telluride nanorod arrays covered conformally with an electrodeposited amorphous nickel molybdenum layer (NiTe@NiMo/NF), which exhibit outstanding SOR performance, capable of delivering 500 mA cm⁻² at only 0.55 V vs. reversible hydrogen electrode (RHE) and operating at 500 mA cm⁻² for 100 hours without degradation, in both simulated and natural seawater. Our comprehensive experimental and theoretical studies reveal that the NiTe@NiMo/NF electrode undergoes a dynamic reconstruction process, and the in situ generated [MoO₄]²⁻ moieties can modulate and stabilize the catalytically active NiTe/NiOOH, improving the SOR activity and stability. Consequently, the asymmetric membrane electrode assembly comprising NiTe@NiMo/NF as the anode can deliver a current density as large as 5.0 A cm⁻² at 1.33 V in alkaline natural seawater at 70 °C and operate at 1.0 A cm⁻² below 1.0 V for 334 hours, holding great potential for energy-saving and cost-competitive hydrogen production from seawater.