Oxygen vacancy-rich nickel-iron hydroxides-derived phosphide with superaerophobic nanoarray morphology for robust overall water splitting

Multiscale engineering of efficient catalysts to optimize the adsorption energy of intermediates (atomic level) and achieve rapid mass transfer (three-dimensional (3D) bulk level) is crucial for boosting overall water splitting. In this work, we first create oxygen vacancies in nickel-iron hydroxide and then transform the hydroxide into NiFe-Vo-P having a nanoarray morphology via phosphorization. During the oxygen evolution reaction, Ni(Fe)OOH and phosphate anions can be in situ formed on the NiFe-Vo-P surface and optimize the adsorption strength of the intermediates. Consequently, NiFe-Vo-P could achieve a high current density of 1.5 A cm−2 at an overpotential of 289 mV. Moreover, the superhydrophilic/superaerophobic nanoarray morphology of NiFe phosphide effectively facilitates the mass transfer, and NiFe-Vo-P achieves current densities of 580 mA cm−2 and 1.0 A cm−2 at a cell voltage of ∼2.0 V at 25 and 70°C, respectively, over twice those of its counterpart without the superaerophobic morphology.