Carbon dot embedded CoNi bimetallic phosphide nanorods as an efficient electrocatalyst for overall water splitting

Efficient bifunctional catalysts for hydrogen/oxygen evolution reactions (HER/OER) are critical for industrial application of overall water splitting. Herein, a self-supported nanostructure consisting of CoNi-P and embedded carbon dots (denoted as CoNi-P/CDs/NF) with large specific surface area has been designed and fabricated, through a phosphorization process on precursors grown on 3D porous Ni foam. The resultant electrocatalyst exhibited excellent electrocatalytic performance for both the HER (45.2 mV@10 mA cm-2) and OER (184.8 mV@20 mA cm-2) under alkaline conditions. The cell voltage of the full water splitting device assembled was only 1.50 V to achieve 20 mA cm-2 and exhibited great durability benefiting from the self-supported nanostructure. The density functional theory (DFT) calculations and XPS analysis suggest that the synergistic coupling effect between CDs and substrate CoNi-P could tune the electronic structure. Moreover, the embedded CDs increase electrical conductivity and active sites of the catalyst. Both of these and the high specific surface benefited from the 1D/3D hierarchical structure could explain the excellent electrocatalytic performance. The rational materials design of 1D/3D hierarchical structured non-noble bimetallic phosphide catalysts in this work may suggest a new strategy for designing bifunctional electrocatalysts.