Hierarchical 3D Oxygenated Cobalt Molybdenum Selenide Nanosheets as Robust Trifunctional Catalyst for Water Splitting and Zinc–Air Batteries

The development of hierarchical nanostructures with highly active and durable multifunctional catalysts has a new significance in the context of new energy technologies of water splitting and metal–air batteries. Herein, a strategy is demonstrated to construct a 3D hierarchical oxygenated cobalt molybdenum selenide (O-Co_{1− x}Mo_xSe₂) series with attractive nanoarchitectures, which are fabricated by a simple and cost-effective hydrothermal process followed by an exclusive ion-exchange process. Owing to its highly electroactive sites with numerous nanoporous networks and plentiful oxygen vacancies, the optimal O-Co_0.5Mo_0.5Se₂ could catalyze the hydrogen evolution reaction and oxygen evolution reaction effectively with a low overpotential of ≈102 and 189 mV, at a current density of 10 mA cm⁻², respectively, and exceptional durability. Most importantly, the O-Co_0.5Mo_0.5Se₂||O-Co_0.5Mo_0.5Se₂ water splitting device only entails a voltage of ≈1.53 V at a current density of 10 mA cm⁻², which is much better than benchmark Pt/C||RuO₂ (≈1.56 V). Furthermore, O-Co_0.5Mo_0.5Se₂ air cathode-based zinc–air batteries exhibit an excellent power density of 120.28 mW cm⁻² and exceptional cycling stability for 60 h, superior to those of state-of-art Pt/C+RuO₂ pair-based zinc–air batteries. The present study provides a strategy to design hierarchical 3D oxygenated bimetallic selenide-based multifunctional catalysts for energy conversion and storage systems.