LAUSR

Abstract In this work, composites of Ni2P/Ni(PO3)2 inlayed in N/S self-doped ultrathin holey carbon nanosheets were facilely prepared using methyl orange (MO) as nitrogen and sulfur sources, in-situ produced Ni(OH)2 nanosheet by hydrolysis of NiCl2 as self-sacrificed template, followed by pyrolysis and phosphorization. Ni2P/Ni(PO3)2 was highly dispersed in carbon nanosheets and supplied fruitful of exposed active sites, and thus endowed the as-prepared samples highly electrocatalytic activities for water splitting. In addition, the N/S self-doped carbon protected Ni2P/Ni(PO3)2 from corrosion by the electrolyte and greatly enhanced the stabilities of the catalysts. As a result, the optimized composite 1:8-NPO/NS-C-420, derived from the precursor with 1:8  molar ratio of MO/Ni(II) and phosphorized at 420 °C, has exhibited excellent electrocatalytic activities for hydrogen evolution reaction (HER), oxygen evolution reaction (OER) and overall water splitting. As a result, 88 mV and 273 mV overpotential was obtained for HER and OER at 10 mA/cm2 in acidic and alkaline electrolyte, respectively. As for the overall water splitting, only 1.63 V of cell voltage is needed to reach 10 mA/cm2. The catalyst also exhibited high long-term stability in HER, OER and water splitting.