Efficient Overall Water Splitting Using NiFe-LDH NanosheetsModified with CoP-Ni₅P₄ Heterojunction NanoarrayElectrodes

Abstract

Nickel–iron layered double hydroxide (NiFe-LDH) has gained recognition as an exemplary transition-metal-based catalyst for the oxygen evolution reaction (OER). However, its performance in the hydrogen evolution reaction (HER) falls short, impeding the overall water splitting (OWS) efficiency. Here, we introduce a self-supporting hierarchical nanostructure material featuring an n–n-type heterojunction, denoted as NiFe-LDH@CoP-Ni₅P₄, strategically designed to address this limitation. This material merges NiFe-LDH with transition metal phosphides (CoP-Ni₅P₄), proving highly effective for both the HER and OER. Utilizing NiFe-LDH@CoP-Ni₅P₄ as the two electrodes for overall water splitting can provide an impressively low cell voltage of merely 1.515 V at 10 mA cm^–2 and have long-term stability (300 h) at 200 mA cm^–2. The n–n junction design represents a strategy for enhancing the electronic structure of the catalysts. Furthermore, the integration of heterojunction substrates offers a promising method for modifying LDH-based materials, ultimately advancing the field of OWS catalysis.