Efficient Alkaline Water/Seawater Electrolysis by Development of Ultra-Low IrO<sub>2</sub> Nanoparticles Decorated on Hierarchical MnO<sub>2</sub>/rGO Nanostructure
S. Karthikeyan, Ramasamy Santhosh Kumar, S. Ramakrishnan, Sampath Prabhakaran, Ae Rhan Kim, Do Hwan Kim, Dong Jin Yoo
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.