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

Development of economical and efficient bifunc-tional 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 (similar to 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 (eta 10 = 190 mV) and the hydrogen evolution reaction (eta 10 = 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.