Metal-Organic Precursors for Transition-Metal-Doped Ni₂P via Pyrolysis for Efficient Overall Water Splitting and Supercapacitance

The synthesis of solvent-less bare-surface nickel phosphides is desired, considering their superior electrocatalytic properties and straightforward synthetic protocols compared to their analogues prepared from colloidal routes. Herein, we report the synthesis of [Ni{S2P(OH)(4-CH3OC6H4)}(2)] (1), [Fe{S2P(OH)(4-CH3OC6H4)}(3)] (2) and [Co{S2P(OC4H9)(4-CH3OC6H4)}(3)] (3) and their utilization to form Ni2P, Fe-Ni2P and Co-Ni2P in a solvent-less pyrolysis method. This solvent-free protocol involved the decomposition of complex (1) and the composites of complex (1) with (2) or (3) in the presence of triphenylphosphine (TPP) at 400 degrees C for one hour. The solvent-less decomposition of complex (1) without TPP formed nickel sulfide. A plausible explanation for this rare fabrication of pristine and doped Ni2P in the absence of any solvent is suggested. All the transition metal doped phosphides improved the HER performance of pristine Ni2P, with the 5 % Fe doped Ni2P having the best performance, requiring 137 mV to reach a current density of 10 mA/cm(2). Similarly, the OER performance of un-doped Ni2P was improved by all the doped Ni2P catalysts, where 10 % Fe-doped Ni2P showed the best performance requiring 326 mV to reach a current density of 10 mA/cm(2). Transition metal doping was also shown to improve the reaction kinetics, stability and durability of the solvent-free prepared Ni2P.