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‐C 3 N 4 hybrids, have been synthesized successfully through a facile in situ co‐precipitation method at room temperature. The CoMn‐LDH@g‐C 3 N 4 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‐C 3 N 4 ( η 50 =−448 mV) requires a potential close to Pt/C ( η 50 =−416 mV) to reach a current density of 50 mA cm 2 . Furthermore, under visible‐light irradiation, the photocurrent density of the CoMn‐LDH@g‐C 3 N 4 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‐C 3 N 4 (0.061 mA cm −2 ), respectively. The CoMn‐LDH@g‐C 3 N 4 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‐C 3 N 4 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‐C 3 N 4 nanosheets as efficient catalysts for renewable energy applications.