Tri-metallic (Mn)CoP2/NiCoP ultrafine nanoparticles constructed by Mn doping as high performance bifunctional electrocatalysts

The most crucial part of electrolyzing water lies in the design and preparation of the catalyst. Manganese-doped metal phosphides are often studied as catalysts for water electrolysis due to their outstanding dual-function properties. In this paper, a two-step method of in-situ hydrolysis and low-temperature phosphating is provided to prepare manganese-doped tri-metallic nickel-cobalt-based phosphides ((Mn)CoP 2 /NiCoPs) ultrafine nanoparticles. It is found that the addition of manganese led to a reduction in the unit cell size of NiCoP and CoP 2 in the catalyst. As the amount of manganese element in the raw materials increases, the doping amount of manganese in the catalyst shows an upward trend. In 1 M KOH, (Mn)CoP 2 /NiCoP-2 with the manganese doping content of 0.35 wt% shows the overpotentials of 52 mV for hydrogen evolution reaction (HER) and 141 mV for oxygen evolution reaction (OER) to achieve 10 mA cm −2 . For total hydrolysis reaction, it requires an overpotential of only 1.50 V in 1 M KOH and 1.48 V in simulated seawater environment. Compared with pure Co 2 P/NiCoP, the catalytic activity of (Mn)CoP 2 /NiCoP-2 is higher. This can be attributed to the doping of manganese, which reduces the oxygen content and particle size of the catalyst, and also optimizes its electronic structure.