Experimental and theoretical investigation of reconstruction and active phases on honeycombed Ni3N-Co3N/C in water splitting

Abstract Honeycombed Ni3N-Co3N decorated with carbon speckles (Ni3N-Co3N/C) is prepared on nickel foam as a potent, economical, and durable water-splitting catalyst. The Ni3N-Co3N/C system has excellent properties in the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), such as low overpotentials of 320/175 mV at 100 mA cm−2, small Tafel slopes of 55.2/70.2 mV dec−1, as well as excellent stability for over 7 days. To demonstrate the commercial practicality, an overall water splitting cell composed of the bifunctional Ni3N-Co3N/C catalyst as both the anode and cathode is assembled and can be driven by a standard 1.5 V battery. Based on experimental and theoretical results obtained by in situ Raman scattering, ex situ XPS, and density-functional theory, the precise effects of the active sites and conductivity, roles of Ni3N, Co3N, and C, and reaction mechanism in HER and OER, are investigated and described.