Magnetic field induced synthesis of (Ni,Zn)Fe2O4 spinel nanorod for enhanced alkaline hydrogen evolution reaction

Recently, the introduction of external fields (light, thermal, magnetism, etc.) during electrocatalysis reactions gradually becomes a new strategy to modulate the catalytic activities. In this work, an external magnetic field was innovatively employed for the synthesis progress of (Ni, Zn)Fe₂O₄ spinel oxide (M-(Ni, Zn)Fe₂O₄). Results indicated the magnetic field (≤250 ​mT) would affect the morphology of catalyst due to the existing Fe ions, inducing the M-(Ni, Zn)Fe₂O₄ nanosphere particles to be uniform and coral-like nanorods. In addition, the electronic structure of the catalyst was regulated by the valence state of Fe, changing the bonding of metal to oxygen atoms in different spinel sites. The results manifested that the M-(Ni, Zn)Fe₂O₄ requires a lower overpotential of only 67 ​mV to deliver 10 ​mA ​cm⁻² for hydrogen evolution reaction (HER) in alkaline electrolyte. Moreover, M-(Ni, Zn)Fe₂O₄ respectively as the anode and cathode electrode for the overall water splitting, the catalysis system requires a cell voltage of only 1.76 ​V to gain a current density of 50 ​mA ​cm⁻², combining with an excellent discharging stability after 10 ​h. This work provides a facile synthesis strategy toward the design of efficient non-noble metal catalysts for alkaline HER and overall water splitting.