Designing AgBi3S5 as an efficient electrocatalyst for hydrogen evolution reaction†

A facile fast synthetic route is designed to prepare a versatile nano-electrocatalyst AgBi₃S₅ (ABS) for the generation of green fuel, H₂, via water electrolysis. The XRD pattern confirms the major formation of monoclinic phase AgBi₃S₅ (ABS) along with binary phase Ag₂S (AS) and Bi₂S₃ (BS). Another variant CuBiS₂(CBS) nanoparticle is synthesized to compare the electrochemical result with the unique sustainable as-synthesized nanoparticles of the ABS compound. Microscopy (HR-TEM) and spectroscopy (FTIR) studies provide confirmational evidence of the syntheses of ABS, AS, BS, and CBS, respectively, while an XPS study confirms the presence of Ag, Bi, and S in ABS. From the electrochemical analysis, it is evident that ABS shows a lower overpotential value of 47 mV compared to those of other variants (AS – 93 mV, BS – 191 mV, CBS – 603 mV) and lower Tafel slope values (mV dec⁻¹) (75.99) than the others (AS – 101.54, BS – 120.29, CBS – 265.2), which are key aspects in analyzing the catalytic activity performance of the catalyst. It is also proved that the rate-determining step of the reaction proceeds through the Volmer–Heyrovsky step. A lower EIS value of 9.84 Ω with a higher active surface area value of 0.092 cm² for ABS indicate superior and effective electron charge transfer kinetics on the electrode–electrolyte interface and elevated activity compared to the other electrocatalysts (AS – 15.24 Ω and 0.035 cm², BS – 16.01 Ω and 0.014 cm², and CBS – 19 Ω and 0.005 cm²). On top of that, an acceleration degradation (AD) study before and after analysis performed at 100 mVs⁻¹ for 500 cycles in acidic solution discloses the fact when comparing the two LSV curves there is a small hike (8 mV at 10 mA cm⁻²), suggesting higher stability and low catalyst degradation for ABS. Chronoamperometric studies with a fixed applied potential of −0.065 V vs. RHE also reveal that the catalyst (ABS) shows retention of activity after a 72 hour long-term process in a cathodic environment.