Mn Doping and P Vacancy Induced Fast Phase Reconstruction of FeP for Enhanced Electrocatalytic Oxygen Evolution Reaction in Alkaline Seawater.

Due to the shortage of pure water resources, seawater electrolysis is a promising strategy to produce green hydrogen energy. To avoid chlorine oxidation reactions (ClOR) and the production of more corrosive hypochlorite, enhancing OER electrocatalyst activity is the key to solving the above problem. Considering that transition metal phosphides (TMPs) are promising OER eletrocatalysts for seawater splitting, a method to regulate the electronic structure of FeP by introducing Mn heteroatoms and phosphorus vacancy on it (Mn-FeP) is developed. As an OER electrocatalyst in seawater solution, the synthesized Mn-FeP achieves extremely low overpotentials (η = 376, η = 395 mV). In addition, the Pt/C||Mn-FeP couple only requires the voltage of 1.81 V to drive the current density of 1000 mA cm for overall seawater splitting. The density functional theory (DFT) calculation shows that Mn-FeP (0.21 e) has more charge transfer number compared with FeP (0.17 e). In-situ Raman analysis shows that phosphorus vacancy and Mn doping can synergistically regulate the electronic structure of FeP to induce rapid phase reconstruction, further improving the OER performance of Mn-FeP. The new phase species of FeOOH is confirmed to can enhance the adsorption kinetics of OER intermediates.