One dimensional nickel phosphide polymorphic heterostructure as carbon-free functional support loading single-atom iridium for promoted electrocatalytic water oxidation

Abstract

Although conducting materials such as carbon nanotube and carbon fiber paper (CFP) have been extensively employed as support of electrocatalytic active sites, most of them are of poor catalytic functionality by themselves and undesirable stability during strong acid/alkaline environments or oxidation process. Here we report a novel one-dimensional (1D) nickel phosphide polymorphic heterostructure (denoted as NPPH) to work as one effective carbon-free functional support for loading of single-atom Ir water oxidation electrocatalyst. Specifically, the NPPH composed of both Ni12P5 and Ni2P phases is not only active for robust alkaline water oxidation but also is of good stability and hydrophilicity for favorable loading of single-atom dispersed iridium. The NPPH supported single-atom Ir electrocatalyst (Ir/NPPH) is found to exhibit remarkably superior water oxidation activity with respect to the NPPH itself or CFP supported single-atom Ir catalyst (Ir/CFP), demonstrating the synergetic promotion effect between NPPH and single-atom Ir catalyst. Furthermore, the NPPH supported single-atom Ir catalyst can bear alkaline water oxidation for over 120 h at current density of 50 mA cm−2. The NPPH developed here is expected as functional support to composite with other water oxidation catalysts, as may be an alternative strategy of developing highly efficient carbon-free electrocatalysts.