Key roles of surface Cr in the NiFe layered double hydroxides for an efficient oxygen evolution reaction via adaptive reconfiguration

Abstract

Cr doping is a new strategy to enhance the OER (Oxygen Evolution Reaction) performance of NiFe-LDH (NiFe-Layered Double Hydroxides) by optimizing surface states and offering a scalable production process. However, as an additive element, Cr itself has weak OER performance, so its promotion on the Ni- and Fe-active site by electron perturbation and structural stabilization in NiFeCr-LDH has been the focus. Herein, a one-step hydrothermal method is used to incorporate Cr into NiFe-LDH, systematically investigating the relationship between Cr content and the material's microstructure. The results of physical characterization show that Cr ion plays a leading role in the electron perturbation Ni/Fe-active center, which causes the increasing of Fe3+ and Ni3+ content. Furthermore, variations in Cr content resulted in the lattice stretching and morphology evolving synchronously. The optimized NiFeCr-LDH exhibited significantly enhanced OER activity and durability compared to undoped NiFe-LDH and outperformed commercial RuO2 catalysts. Additionally, a microstructure comparison was made between the initial- and long-term used-NiFeCr-LDH. The findings reveal that the material's distinctive structural evolution behavior confers it with exceptional self-adaptability to the OER reaction, which results in a consistent enhancement of activity lasting up to 12 h during long-term I-t test showing a new idea for the design of high performance NiFeCr-LDH.