Industrial application of overall water splitting requires developing readily available, highly efficient, and stable oxygen evolution electrocatalysts that can efficiently drive large current density. This study reports a facile and practical method to fabricate a non-noble metal catalyst by directly growing a Co-Fe Prussian blue analogue on a 3D porous conductive substrate, which is further phosphorized into a bifunctional Fe-doped CoP (Fe-CoP) electrocatalyst. The Fe-CoP/NF (nickel foam) catalyst shows efficient electrocatalytic activity for oxygen evolution reaction, requiring low overpotentials of 190, 295, and 428 mV to achieve 10, 500, and 1000 mA cm-2 current densities in 1.0 m KOH solution. In addition, the Fe-CoP/NF can also function as a highly active electrocatalyst for hydrogen evolution reaction with a low overpotential of 78 mV at 10 mA cm-2 current density in alkaline solution. Thus, the Fe-CoP/NF electrode with meso/macropores can act as both an anode and a cathode to fabricate an electrolyzer for overall water splitting, only requiring a cell voltage of 1.49 V to afford a 10 mA cm-2 current density with remarkable stability. This performance appears to be among the best reported values and is much better than that of the IrO2-Pt/C-based electrolyzer.
Keywords: Prussian blue analogues; bifunctional electrocatalysts; large current density; oxygen evolution.