Crystalline CoP@ Amorphous WP2 Coaxial Nanowire Arrays as Bifunctional Electrocatalyst for Water Splitting

The crystalline CoP@ amorphous WP 2 core–shell nanowire arrays are oriented grown on the Ni foam (CoP@WP 2 /NF). The amorphous WP 2 shell provides more active sites, and the interface charge coupling accelerates the kinetic of the catalytic reaction, making the CoP@WP 2 /NF catalysts excellent activity. In acidic, only 13 and 97 mV overpotentials are needed to reach 10 mA cm −2 and 100 mA cm −2 , respectively, which are the lowest overpotentials among all reported Transition metal phosphide (TMP) catalysts, of course, much lower than that of the Pt/C catalyst (31 mV at 10 mA cm −2 , 120 mV at 100 mA cm −2 ). In alkaline, the Hydrogen evolution reaction (HER) overpotentials at 10 mA cm −2 and 100 mA cm −2 are 68 and 136 mV, respectively, which are also lower than that of most reported TMPs catalysts. The CoP@WP 2 /NF catalysts also show excellent Oxygen evolution reaction (OER) performance in alkaline, and its OER overpotential at 10 mA cm −2 is only 254 mV. The voltage of the CoP@WP 2 /NF-2h‖CoP@WP 2 /NF-2 h cell is only 1.37 V at 10 mA cm −2 , which is even lower than that of Pt/C‖Ru 2 O cell (1.52 V). Specially, when the current density is greater than 150 mA cm −2 , the energy consumption advantage of the CoP@WP 2 /NF-2 h‖CoP@WP 2 /NF-2 h cell is more obvious.