Iron-induced charge density redistribution of medium entropy alloys for ampere-level seawater electrolysis

Abstract

Electrocatalytic seawater splitting into green hydrogen provides a promising strategy for clean and sustainable energy conversion. Designing cost-effective electrocatalyst with high activity and robust stability is pivotal for achieving industrial-scale green hydrogen generation by alkaline seawater electrolysis. Herein, a cost-effective and high-performance FeCoNi medium-entropy alloys electrocatalyst was obtained via a feasible electrodeposition strategy. Due to the synergistic interaction of multi-component, the obtained FeCoNi electrocatalysts exhibit an outstanding oxygen evolution reaction (OER) performance, requiring overpotential input of as low as 315, 353 and 402 mV to produce industrial-level current density of as high as 500, 1000 and 1500 mA cm⁻², respectively, along with Tafel slope of 32 mV/dec in 1.0 M KOH electrolyte. In addition, the as-synthesized FeCoNi electrocatalysts represent an excellent performance toward electrocatalyzing seawater oxidation. In alkaline natural seawater electrolyte, FeCoNi could even produce an industrial current density of 1000 mA cm⁻² at overpotential input of 390 mV, representing high activity and corrosion-resistant in chloride environment of seawater. Remarkably, the rationally designed anode can stably operate for over 2000 h at an industrial-relevant current density of 500 mA cm⁻² in an alkaline electrolyze. In-situ Raman spectroscopy reveal Fe species could reconfigure electronic distribution, resulting in high-valent M (M = Co or Ni active sites) active sites for water oxidation in alkaline electrolyte. Moreover, Fe, as electron acceptor, could efficiently accelerate the charge transfer kinetics and build the high-efficient spatial charge separation for optimized valence band maximum and work function. Such a novel charge density reconfiguration not only facilitates the tensile lengthening of O–H bond, but also repulses undesirable anion adsorption, achieving a high-performance and robust water oxidation in alkaline electrolyte.