Hydrothermal construction of flower-like CuS microsphere electrocatalysts for hydrogen evolution reactions in alkaline fresh water, alkaline seawater, and seawater

Green hydrogen energy production from electrocatalysts produced via low-temperature hydrothermal method with easy preparation and cost effectiveness has attracted attention as an alternative to high-temperature nitration, phosphide, and sulfonation processes. Hence, in this work with consideration of previous works, we have prepared low temperatures (60 degrees C-80 degrees C) surfactant assisted copper sulfide (CuS) spherical flower-like microsphere morphologies with the help of the hydrothermal technique. The product exhibited a single CuS covellite phase at 60 degrees C, whereas the increase in hydrate phase was also observed along with the CuS phase at 70 degrees C and 80 degrees C. SEM and TEM analyses revealed that increase in the size of flower-like microsphere morphology with the covellite phase was observed with an increase in reaction temperatures. The vibrational mode at 616 and 472 cm(-1) confirmed the formation of CuS in FTIR and Raman spectra respectively. The CuS catalyst obtained at 80 degrees C achieved low 176, 199, and 458 mV overpotentials to get 10 mA/cm(2) in 1 M KOH of distilled water, 1 M KOH of seawater, and natural seawater compared to other CuS catalysts on account of the higher surface area of 16.19 m(2)/g. The CuS catalyst prepared at 80 degrees C showed low charge transfer resistance (R-ct) at catalyst/seawater interface compared to other catalysts with the retention of 74.1% in natural seawater after 10 h stability examination. Structural and compositional studies of the CuS catalyst prepared at 80 degrees C after 10 h stability examination confirmed white Mg(OH)(2) and Ca(OH)(2) precipitate formation on CuS surface.

Automated summary

This study prepared surfactant-assisted copper sulfide (CuS) spherical flower-like microspheres through a low-temperature hydrothermal method. The size of the flower-like microspheres increased with the reaction temperature. The CuS catalyst prepared at 80℃ showed low overpotentials and charge transfer resistance in seawater, indicating good stability.