Interfacial Engineering of the CoxP–Fe2P Heterostructure for Efficient and Robust Electrochemical Overall Water Splitting

Development of efficient, stable, and low-cost noble metal-free electrocatalysts for overall water splitting is of great significance for sustainable energy conversion, yet it remains highly challenging. Herein, a CoxP–Fe2P heterostructure array electrocatalyst supported on nickel foam (CoxP–Fe2P/NF) is fabricated via phosphating of the CoFe-layered double hydroxide (CoFe-LDH) nanosheets decorated with CoFe Prussian blue analogue (CoFe-PBA) nanocubes. The as-fabricated CoxP–Fe2P/NF heterostructure arrays with an abundant and strongly electronic coupled interface not only guarantee the fast charge transfer and improve the reaction kinetics but also enable the charge redistribution between CoxP and Fe2P, thus possibly optimizing the adsorption capabilities of reactants. Benefiting from the compositional and structural advantages, this as-fabricated CoxP–Fe2P/NF heterostructure can efficiently convert water to H2 and O2 with the potentials of 75 and 265 mV to achieve the current densities of 10 and 50 mA cm–1 in 1 M KOH, respectively. Especially, when CoxP–Fe2P/NF is used as both anode and cathode materials, a cell voltage of 1.61 V is required at the current density of 10 mA cm–2 with excellent stability in long-term operation over 100 h, which is comparable to Pt/C/NF||RuO2/NF. This work highlights the key roles of the interface in accelerating the electrocatalytic reaction kinetics and paves a way for the design of a high-performance electrocatalyst for overall water splitting.