High-throughput electrochemical strategy for synthesis of iron-based nanostructures for electrocatalytic water splitting

Electrochemical water splitting has drawn significant attention for hydrogen generation as a carbon-free energy carrier for the construction of a net-zero society. To scale up water electrolyzers, enormous efforts have been made to the development of high-throughput synthesis of the electrocatalysts based on abundance and non-toxic elements for both oxygen and hydrogen evolution reactions. In this work, Fe-based nanostructures with a high Fe electrooxidation rate (up to 1 g cm⁻² h⁻¹) were prepared through a controlled and feasible electrosynthesis using pulse alternating current. The effect of electrolyte solution and post-annealing on composition/structural characteristics and electrochemical activity of the Fe-based nanostructures was depicted. The bi-phase sheet-like γ-Fe₂O₃/δ-FeOOH and cube-like γ-Fe₂O₃/α-FeOOH structures are formed in aqueous NaOH and NaCl solutions, respectively. The electrocatalytic activity of the synthesized structures was tailored by annealing up to 500 °C in air. The α-Fe₂O₃ catalyst synthesized in NaOH and NaCl demonstrated the overpotentials of 441 and 390 mV at 10 mA cm⁻² in hydrogen and oxygen evolution reactions, respectively. This work provides new and deep insights into the high-throughput electrosynthesis of low-cost catalysts for hydrogen and oxygen production from water splitting. Therefore, this work focuses on the rational design and research of Fe-based catalysts for electrochemical water splitting.