Realizing tailored catalytic performance on ternary FeP-Ni5P4-CoP in-situ confined Prussian blue analogue framework for anion exchange membrane water electrolysis

Abstract

The development of highly efficient electrocatalysts to enhance the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in overall water splitting (OWS) has become a central focus to produce clean fuel for achieving a net-zero emission society. In this work, we introduce a novel bifunctional catalyst comprising ternary FeP-Ni₅P₄-CoP clusters uniformly incorporated within a Prussian blue analogue (PBA) framework (FeP-Ni₅P₄-CoP/PBA), with robust structural integrity, enhanced porosity, and an enlarged active surface area, thus enabling outstanding catalytic performances. The FeP-Ni₅P₄-CoP/PBA requires a low overpotential of 99 ± 4 mV towards HER at 10 mA·cm⁻² and 300 ± 7 mV towards OER at 50 mA·cm⁻² in 1.0 M KOH, surpassing its analogues. The experimental and theoretical studies indicate that the formation of ternary metal phosphide heterostructures within a porous coordination polymer framework facilitates rapid charge conductivity and desirable mass transfer and generates multiple active sites with optimum electronic properties to boost activity and stability towards HER and OER kinetics. The practicality of FeP-Ni₅P₄-CoP/PBA material is validated by deploying it in an anion exchange membrane water electrolyzer (AEMWE) stack, which delivers a high current density of 500 mA cm⁻² at a required voltage of 2.20 ± 0.02 V at 70 °C in alkaline electrolyte and remarkable stability exceeding 500 h accompanied by insignificant voltage loss.