Confined synthesis of highly dispersed Ni anchored on mesoporous carbon as efficient catalyst for water splitting

Developing an efficient and low-cost bifunctional electrocatalysts with superior activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is highly required but still challenging. Herein, highly dispersed Ni species containing both Ni nanoparticles (NPs) and atomically dispersed Ni-NX on mesoporous nitrogen-doped carbon (Ni-N-C) were prepared by a facile one-pot pyrolysis strategy using dicyandiamide, citric acid and nickel acetylacetonate as raw materials. The confinement agent citric acid is quite requisite for dispersing Ni NPs and forming mesoporous graphene-like carbon substrate. Due to the uniform size of Ni NPs (3 nm) and the synergistic effect between Ni NPs and Ni-NX, and the unique mesoporous carbon structure, such Ni-N-C catalyst exhibits favorable activities for both HER and OER. The overpotentials for HER and OER are only 218 and 330 mV vs. RHE on glassy carbon to deliver a current density of 10 mA & BULL;cm  2, respectively. Moreover, this catalyst also showed good operation durability with no obvious deactivation after long-term (18 h) potentiostatic electrolysis or continuous CV tests. This work could offer a new avenue for the design of bifunctional electrocatalysts in efficient water splitting.