Ligand-Tuned Energetics for the Selective Synthesis of Ni2P and Ni12P5 Possessing Bifunctional Electrocatalytic Activity toward Hydrogen Evolution and Hydrazine Oxidation Reactions

Ni12P5 and Ni12P5-rGO for multifunctional electrocatalyst and supercapacitor application

Transition metal phosphides are crucial for various environmental and energy applications. In this study, porous Ni12P5 and Ni12P5-rGO were synthesized using a one-step solvothermal method. Red phosphorus served as the phosphorus source, while ethylene glycol acted as a capping agent to promote the formation of nanomaterials within a nitrogen-rich atmosphere. The catalytic performance of these materials was evaluated through their hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and capacitance properties. Notably, Ni12P5-rGO exhibited Tafel slopes of 66 mV/dec for OER and 33 mV/dec for HER, indicating enhanced charge transfer efficiency compared to Ni12P5, which showed slopes of 78 mV/dec and 102 mV/dec, respectively. This improvement suggests that Ni12P5-rGO facilitates faster electron transfer, resulting in superior catalytic performance. Additionally, the synergistic effect of reduced graphene oxide (rGO) contributes to improved charge storage capabilities. The Ni12P5-rGO demonstrated a specific capacitance of 192 F/g, significantly higher than the 110 F/g observed for Ni12P5 at a current density of 1 A/g. Remarkably, these materials maintained their capacity over 5000 cycles, achieving a commendable 98 % coulombic efficiency. These findings highlight the potential of Ni12P5-rGO as an effective material for energy conversion and storage applications, showcasing its promising role in advancing the efficiency of related technologies.

Facile preparation of nickel phosphide for enhancing the photoelectrochemical water splitting performance of BiVO4 photoanodes

The photoelectrochemical (PEC) water splitting performance of BiVO₄ (BVO), a promising photoanode material, is constrained by its extremely short hole diffusion length and slow water oxidation kinetics. Modification of oxygen evolution cocatalysts (OECs) by appropriate methods is a practical solution to enhance the PEC water splitting performance of BVO. In this work, two different nickel phosphides Ni₂P and Ni₁₂P₅ were prepared by a facile and mild one-step solvothermal method, and used as OECs to modify a BVO photoanode for enhancing the PEC water splitting performance. The BVO/Ni₂P and BVO/Ni₁₂P₅ photoanodes showed impressive photocurrent densities of 3.3 mA cm^-2 and 3.1 mA cm^-2, respectively. In addition, the PEC water splitting stability of the BVO/Ni₂P photoanode was greatly enhanced compared to that of the bare BVO photoanode. Further characterization and photoelectrochemical analysis revealed that the significant improvement of the BVO photoanode performance was attributed to the effective inhibition of surface charge recombination, facilitation of interfacial charge transfer, and acceleration of water oxidation kinetics after Ni₂P and Ni₁₂P₅ modification.