Identifying the Key Factors for Boosting NiFe-LDH with Optimized Bifunctional HER/OER Activities

Although nickel–iron layered double hydroxide (NiFe-LDH) demonstrates promising oxygen evolution reaction (OER) performance, its inherently limited hydrogen evolution reaction (HER) activity restricts its application as a bifunctional electrocatalyst for alkaline water splitting. This study describes the development of an ultrafast self-heating coprecipitation method for synthesizing low-crystallinity NiFe-LDH as a model catalyst, with precise control over the Ni/Fe atomic ratio, vacancy concentration, and crystallinity. Multivariate trend analysis was performed to systematically decouple the individual and synergistic effects of these parameters on the intrinsic OER and HER activities of NiFe-LDH. The findings of the study highlight the critical role of iron vacancies in boosting the bifunctional activities of NiFe-LDH by electronically modulating Ni sites, with a Ni/Fe atomic ratio of approximately 1:1 and sufficiently low crystallinity achieving optimized OER and HER activities. This study helps to establish mechanistic design rules for NiFe-LDH–based bifunctional electrocatalysts and demonstrates a broadly applicable synthesis–analysis framework for advancing cost-effective water splitting.