Polyaniline grafted mesoporous zinc sulfide nanoparticles for hydrogen evolution reaction

Numerous efforts have been directed to fabricate the cost-effective structure for hydrogen evolution reaction (HER). However, it is still a challenging task for clean energy. Herein, mesoporous zinc sulfide nanoparticles with various contents of polyaniline have been synthesized using the solvothermal process. Morphological and structural analysis has been carried out in detail for HER activity in KOH electrolyte at pH 10.20 and 13.55. The hybrid of zinc sulfide and Polyaniline (ZnS-90 mg), exhibits a lower specific surface area of 5.54 m2 g-1 and a greater mesoporous size of 10.10 nm as compared to individual polyaniline nanofibers (75.13 m2 g-1 and 6.02 nm) and zinc sulfide nanoparticles (80.90 m2 g-1 and 6.81 nm) due to interface, which creates the unique characteristics as compared to PANI-Nbs and ZnS-NPs. Hybrid ZnS-90 mg, synergistically, exhibits the greater electrical conductivity of 17.90 × 10−4 Scm−1 and reveals the lower over potential of 168 mV with an onset potential of 41 mV at pH 13.55, and an over potential of 345 mV with an onset potential of 69 mV at pH 10.20 of 1 M KOH for HER activity at the state of art current density of 10 mAcm−2. Hybrid ZnS-90 mg also shows the smaller Tafel slope of 234 mVdec−1 with the greater turnover frequency of 5.22 ms-1 at pH 13.55, recommending the better HER activity. A symmetric system consisting of Hybrid ZnS-90 mg reveals the two reduction peaks, where the over potential has been measured as 524 mV at the current density of 2.76 mAcm−2 and 947 mV at the current density of 10 mAcm−2 at pH 13.55. The symmetric system exhibits a good Tafel slope of 26 mVdec−1 and suggests it is the suitable and cost-effective electrode structure for HER to produce clean hydrogen energy.