Bifunctional FeCoP/C electrocatalyst toward overall water splitting by application of various dimensional carbon materials

Water electrolysis is a green, safe, and practical route for hydrogen refueling station, but now it confronts a big challenge of extremely high electrical energy consumption. Thus, lower the voltage of an electrolyzer is one of the critical routes to solve this issue. Here we apply carbon black Vulcan XC-72, carbon nanotubes, and graphene oxide (named as 3C) to construct an effective bifunctional iron cobalt phosphide (FeCoP/3C) electrocatalyst, the electrocatalytic activity toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) was respectively investigated. The FeCoP/3C electrocatalyst shows overpotential of 220 mV and 120 mV at current density of 10 mA cm−2, Tafel slope of 73 mV dec−1 and 129 mV dec−1 for OER and HER in 1 M KOH electrolyte, respectively. When the electrocatalyst is used to construct an overall water electrolyzer, a cell voltage of 1.597 V can be achieved at current density of 10 mA cm−2. Moreover, the FeCoP/3C displays excellent durability toward overall water splitting, because the current density retains 92% after working for 10 h continuously. This outstanding performance is mainly attributed to the electrocatalyst possessing excellent electrical conductivity, exposing sufficient active sites, facilitating fast ions transportation and electron transfer, as well as speeding up O2 and H2 release. Therefore, this FeCoP/3C electrocatalyst can be a promising bifunctional electrocatalyst for practical overall water splitting.