Growth of NiAl-LDH Nanoplates on NiFe Foam and Their Enhanced Electrochemical Properties for Oxygen Evolution Reaction

The development of sustainable energy that does not emit carbon pollutants is a major research topic toward minimizing waste generation and ecosystem degradation caused by the use of fossil fuels. Electrochemical water splitting is a semipermanent cycle that produces energy with zero carbon emissions. It is an innovative science and technology for a sustainable future for humanity and nature. However, its high operating potential due to the four-electron transfer process of the oxygen evolution reaction (OER) at the anode is the main factor hindering the overall reaction rate. Thus, given the importance of operating this cycle with high efficiency, studies have been extensively conducted to enhance the activity of transition-metal-based layered double hydroxide (LDH) catalysts. The use of metal foam as a substrate for LDH growth is considered the most effective method. However, most studies aimed at improving the performance of heterostructured catalysts have generally focused on controlling the active materials grown on the foam rather than the foam itself. Herein, we propose a new perspective on the role of foam, emphasizing that it is more than a mere supporting medium for growth. Density functional theory (DFT) calculations were performed to investigate the effects of NiFe foam (NFF) by modeling a heterostructure comprising NiAl-LDH and NFF. The calculation results demonstrated electron redistribution at the NiAl-LDH@NFF interface, which effectively influenced the OER performance and interfacial binding energy. Furthermore, we obtained insights into the role of foam by investigating changes in the OER overpotential caused by differences in the elements comprising the foam (Ni foam, 327 mV at 10 mA cm−2; NFF, 214 mV at 10 mA cm−2). This study affords flexibility in the utilization of metal foam-based heterostructured catalysts.