Surface phosphorization of nickel oxalate nanosheets to stabilize ultrathin nickel cyclotetraphosphate nanosheets for efficient hydrogen generation

Abstract The generation of renewable energy through electrochemical water splitting (oxygen evolution reaction and hydrogen evolution reaction) is currently thrust research area due to the low cost and environmental friendly process. To meet our energy requirements a lot of efforts are going into designing of non-noble earth-abundant material for the production of H2. In the present study, ultrathin nickel cyclotetraphosphate (Ni2P4O12) nanosheets (thickness ∼ 1.5 nm) have been stabilized at low temperature using nickel oxalate nanosheets and di-phosphorus pentaoxide as a starting material. The synthesis of nickel oxalate nanosheets (thickness ∼5−6 nm) has been done at room temperature using a simple micellar route wherein CTAB has been used as a surfactant. Nickel cyclotetraphosphate (sample S4) shows an overpotential of 105 mV measured at 10 mV/cm2 current density, Tafel slope of ∼ 48 mV/dec and stability up to 17 h.