Ni-phosphates, novel electrode materials due to their high redox features, could be utilized as multi-functional materials for hydrogen and oxygen evolution processes and charge storage applications, however, their performance can be further improved by regulating their morphology and electrical structure which is still challenging. Herein, a novel solvent-assisted approach to modify the Ni- phosphates' phase, growing Ni₂P, Ni₁₂P₅, and Ni(PO₃)₂ crosslinked ultrathin nanosheets on Ni-foam, using the same precursor under different solvents was developed. Compared to Ni₂P and Ni₁₂P₅, Ni(PO₃)₂ sample showed outstanding activity and endurance towards hydrogen evolution reaction (134 mV overpotential @10 mV/cm² and 112 mV/dec Tafel slope) and oxygen evolution reaction (354 mV overpotential @10 mV/cm² and 60 mV/dec Tafel slope). Theoretical calculations showed that the density of states and their distribution across the Fermi level increased in the order of Ni₂P<Ni₁₂P₅<Ni(PO₃)₂, which improved their conductivity and electronic properties, benefiting electrocatalytic activities. Moreover, the synergistic effect between Ni and P corroborates significant improvement in the electrochemical charge-storing ability. The synthesized materials were further examined under the prelims of the supercapacitor and found that the Ni(PO₃)₂ outcast the highest specific capacitance of 4366 mF/cm² at 10 mV/s and 7582 mF/cm² at 1 mA/cm². It can maintain 97% capacitance retention and 100% coulombic efficiency during 5000 cycles of charge-discharge studies. Such a strategy for fabricating nanostructured materials which efficiently produce and store energy is much required for advancement in green energy production and storage.

Tim Dawsey

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