Preparation of a Pt-Ni2P/NF catalyst for highly efficient hydrogen evolution using a magnetic field to promote Ni-Pt galvanic replacement

The noble metal Pt is an ideal catalyst for promoting the hydrogen evolution reaction (HER) during the electrolysis of water. However, Pt is also expensive and suffers from low utilization rates. In this work, a Pt-Ni2P/NF nanorod catalyst with a low Pt loading was synthesized under different magnetic fields, and it was found that the application of a magnetic field can increase the rate of the galvanic replacement reaction. When the magnetic field strength increases from 0 to 600 mT, the chemical reaction rate increases gradually, and the utilization rate of Pt increased by 2.3 times under 600 mT. The mechanism of the magnetic field-induced magnetohydrodynamic (MHD) effect on the galvanic replacement reaction was revealed. In a 1 M KOH solution and at a current density of 10 mA cm–2, the overpotential of Pt-Ni2P/NF prepared by applying a 600 mT magnetic field was as low as 15 mV and the Tafel slope was 37 mV dec–1, compared with values of 82 mV and 70 mV dec–1 for a specimen prepared without a magnetic field. Additionally, at an overpotential of 90 mV, the mass-based Pt activity of the former material was 12 times greater while its turnover frequency was 19 times greater. This work provides theoretical and technical knowledge expected to assist in the controllable preparation of materials in magnetic fields and the efficient utilization of metallic resources.