Design of tin polyphosphate for hydrogen evolution reaction and supercapacitor applications

With the ever-growing demand for clean and viable energy sources, the possibility and need to use a multifunctional energy system having integrated energy storage and conversion capacity has been intensified in current times. To fulfill this requirement, a search for an active material having an efficient bifunctional capacity of both hydrogen evolution reaction (HER) and supercapacitor is an essential requirement. The metal polyphosphate with the advantage of abundance, environmental friendliness, low cost, and reliable activity make it an emerging class of novel material for the present research. Herein, for the first time, the comparison of the amorphous and crystalline form of tin polyphosphate-based electrode was assessed toward hydrogen evolution reaction and supercapacitor. Considering the synergistic influence of abundant tin polyphosphate and the three-dimension structure of nickel substrate, we unswervingly deposited well-defined hierarchical in-situ amorphous SnPxOy and ex-situ crystalline SnPxOy over Ni foam using the one-step hydrothermal route. Impressively, amorphous SnPxOy/NF electrode required less over the potential of the only 100 mV with Tafel slope of 50 mV dec−1 to attain a current density of 10 mA cm−2 in comparison to crystalline SnPxOy/NF electrode showing over the potential of the only 170 mV with Tafel slope of 80 mV dec−1 to attain the same current density in 1 M KOH. Additionally, we investigated this electrode in a supercapacitor and found that amorphous SnPxOy/NF delivers a good specific capacitance of 580 F g−1 at a current density of 1 A g−1, greater rate capability, and cyclic stability. Hopefully, this study may demonstrate a promising technique for the preparation of ample, low-cost electrodes for future applications in both HER and supercapacitors applications.