Enhanced electrocatalytic overall alkaline water splitting induced by interfacial electron coupling of Mn3O4 nano-cube@CeO2/γ-FeOOH nanosheet hetero-structure

Abstract

The development of efficient and durable transition metal-based bifunctional electrocatalysts for overall water splitting and cost-effective production of green hydrogen is highly necessary to overcome the adverse environmental effect of non-renewable energy sources. Herein we have developed an aqueous solution-based simple, scalable and one-pot strategy for the synthesis of arrayed γ-FeOOH nanosheets and CeO₂ nanoparticle loaded Mn₃O₄ nano-cubes (Mn₃O₄@CeO₂/γ-FeOOH) at room temperature. The synthesized Mn₃O₄@CeO₂/γ-FeOOH showed superior HER and OER activities at both lower and higher current density (η₁₀: 190 mV and η₁₀₀₀: 300 mV for OER, and η₁₀: 180 mV and η₁₀₀₀: 420 mV for HER) and excellent stability of 50 hours at a current density of 1 A cm⁻². The respective two-electrode electrolyser with the developed catalyst in both anode and cathode demanded a potential of 1.55 V and 2.06 V to drive 10 mA cm⁻² and 1 A cm⁻² current density, respectively. Most importantly, it also showed outstanding water splitting performance in a 2 cm × 2 cm prototype anion exchange membrane (AEM) electrolyser and reached a current density of 366 mA cm⁻² at an applied potential of 2 V. The developed catalyst showed outstanding stable performance for 100 hours at a current density of 1 A cm⁻² in both the two electrode electrolyser as well as the prototype AEM electrolyser. Characterization results revealed that the origin of enhanced electrocatalytic activity is not only from the microstructure and high surface area (313 m² g⁻¹) but also due to the interfacial partial electron transfer between the constituent components Mn₃O₄, CeO₂ and γ-FeOOH. Thus, the simple and scalable synthesis strategy of the catalyst and its superior and stable electrocatalytic activity, particularly in AEM electrolyser, suggest that the developed catalyst Mn₃O₄@CeO₂/γ-FeOOH might be an alternative to the PGM-based catalyst for large-scale hydrogen production through AEM electrolyser.