Coupling of Bifunctional CoMn‐Layered Double Hydroxide@Graphitic C₃N₄ Nanohybrids towards Efficient Photoelectrochemical Overall Water Splitting

Abstract

The development of durable, low-cost, and efficient photo-/electrolysis for the oxygen and hydrogen evolution reactions (OER and HER) is important to fulfill increasing energy requirements. Herein, highly efficient and active photo-/electrochemical catalysts, that is, CoMn-LDH@g-C₃ N₄ hybrids, have been synthesized successfully through a facile in situ co-precipitation method at room temperature. The CoMn-LDH@g-C₃ N₄ composite exhibits an obvious OER electrocatalytic performance with a current density of 40 mA cm^-2 at an overpotential of 350 mV for water oxidation, which is 2.5 times higher than pure CoMn-LDH nanosheets. For HER, CoMn-LDH@g-C₃ N₄ (η₅₀ =-448 mV) requires a potential close to Pt/C (η₅₀ =-416 mV) to reach a current density of 50 mA cm² . Furthermore, under visible-light irradiation, the photocurrent density of the CoMn-LDH@g-C₃ N₄ composite is 0.227 mA cm^-2 , which is 2.1 and 3.8 time higher than pristine CoMn-LDH (0.108 mA cm^-2 ) and g-C₃ N₄ (0.061 mA cm^-2 ), respectively. The CoMn-LDH@g-C₃ N₄ composite delivers a current density of 10 mA cm^-2 at 1.56 V and 100 mA cm^-2 at 1.82 V for the overall water-splitting reaction. Therefore, this work establishes the first example of pure CoMn-LDH and CoMn-LDH@g-C₃ N₄ hybrids as electrochemical and photoelectrochemical water-splitting systems for both OER and HER, which may open a pathway to develop and explore other LDH and g-C₃ N₄ nanosheets as efficient catalysts for renewable energy applications.