In-situ construct Ni2P/Ni5P4 heterostructured electrocatalyst through controllable Ni2P phase transition for enhanced HER performance

In NiP-based catalysts, although Ni 2 P and Ni 5 P 4 have relatively high catalytic activity, the catalytic performance of single-phase Ni 2 P or Ni 5 P 4 is still far from that of noble metal catalysts. The dual-phase heterojunction has better catalytic performance than single-phase materials due to its faster interface charge transfer rate and more active sites. The Ni 2 P/Ni 5 P 4 @CC heterostructural catalyst with oriented porous nanosheet arrays grown on carbon cloth (CC), was in-situ constructed through the controllable phase transition of Ni 2 P. By modulating the amount of P source (P-dependent) or the phosphating reaction time (Time-dependent), the degree of the Ni 2 P phase transition could be modulated, thus obtaining the Ni 2 P/Ni 5 P 4 @CC heterostructural catalyst with the required component ratio of Ni 2 P and Ni 5 P 4 . When the ratio of Ni 2 P and Ni 5 P 4 was 15.7:84.3, the Ni 2 P/Ni 5 P 4 @CC catalyst had the best catalytic performance. Its hydrogen evolution reaction (HER) overpotentials were only 139 and 87 mV overpotentials reaching −10 mA/cm 2 in 1 mol/L KOH and 0.5 mol/L H 2 SO 4 , respectively, which was much lower than that of the single-phase Ni 2 P@CC (base: 278 mV; acid: 123 mV) and Ni 5 P 4 @CC (base: 166 mV; acid: 106 mV) catalysts. Specially, in acidic electrolyte, HER overpotential at a higher current density of −100 mA/cm 2 of the Ni 2 P/Ni 5 P 4 @CC catalyst was 270 mV, which was even lower than that of the Pt/C catalyst (328 mV), indicating that the Ni 2 P/Ni 5 P 4 @CC heterostructural catalysts had promising prospects for commercial applications. The mechanism of catalytic performance enhancement was investigated by the density functional theory (DFT) calculations.