Efficient Alkaline Water/Seawater Electrolysis by Development of Ultra-Low IrO2 Nanoparticles Decorated on Hierarchical MnO2/rGO Nanostructure

Abstract

Development of economical and efficient bifunctional electrocatalysts for the alkaline water/seawater electrolysis becomes essential for industrial hydrogen production. Herein, we developed a rational design for a bifunctional electrocatalyst with ultra-low (∼3.7%) loading of iridium oxide nanoparticles anchored on a hierarchical manganese oxide sheet grown in reduced graphene oxide (IrO₂@MnO₂/rGO) through a cost-effective hydrothermal and calcination route. The optimized IrO₂@MnO₂/rGO shows enhanced bifunctional activity toward the oxygen evolution reaction (η₁₀ = 190 mV) and the hydrogen evolution reaction (η₁₀ = 170 mV) in a 1.0 M KOH electrolyte due to a larger electrochemical surface area of hierarchical MnO₂/rGO with a greater number of IrO₂ active sites and a strong synergistic effect between IrO₂ and MnO₂. The fabricated IrO₂@MnO₂/rGO||IrO₂@MnO₂/rGO water-splitting device exhibits cell voltage comparable to benchmark Pt–C||IrO₂ and remarkably higher durability of about 300 h. The post-morphological studies of the optimized IrO₂@MnO₂/rGO catalyst reveal significant retention of IrO₂ nanoparticles in the IrO₂@MnO₂/rGO electrocatalyst. For practical applications, we fabricated IrO₂@MnO₂/rGO||IrO₂@MnO₂/rGO natural seawater water-splitting device and it displayed a lower cell voltage of 1.64 V at a current density of 10 mA cm^–2. This paves a potential pathway toward the design of an efficient, durable, and bifunctional electrocatalyst for clean hydrogen production and alkaline water/seawater electrolysis.