Improved OER catalytic performance of NiFe-LDH with hydrothermal carbonization microspheres

The electrochemical oxygen evolution reaction (OER) is a fundamental anodic semi-reaction used in the hydrogen energy industry. Herein, we report a novel NiFe-layered double hydroxide (NiFe-LDH)-based hybrid catalyst for the OER, which is promoted by the two-step hydrothermal loading of carbon sphere (CS) onto NiFe-LDH sheets, named as NiFe-LDH@CS. The effects of hydrothermal carbonization (HTC) parameters (such as hydrothermal time and glucose concentration) and the loading ratio of CSs on NiFe-LDH@CS were investigated. The results showed that the two-step hydrothermal synthesis significantly inhibited the interference of the carbonized substances on the lattice formation of NiFe-LDH and successfully achieved a firm combination. By adjusting the HTC process, the surface characteristics and graphitization degree of the carbonized microspheres can be effectively controlled, leading to increased OER performance of NiFe-LDH@CS. Thus, under the optimal process parameters (5 h, 0.6 M, and 5 mL), NiFe-LDH@CS exhibited an excellent overpotential of 292 mV at 50 mA cm -2 and 372 mV at 100 mA cm -2 for the OER. The outstanding OER performance of NiFe-LDH@CS is attributed to the excellent morphology control of the composite, abundant functional groups, and suitable graphitization degree of the hydrothermally carbonized CS, as well as the synergistic effect between the CSs and NiFe-LDH.