Study of direct current electrocatalytic hydrogen evolution on bismuth (111) electrode in diluted acidic solutions

Abstract

This thesis investigates the Hydrogen Evolution Reaction (HER) on Bismuth (111) single crystal electrodes in dilute acidic solutions (pH 2.0 to 3.5) to validate a robust chronopotentiometric model that characterizes the transition from proton reduction to water reduction and identifies the specific moment of near-electrode alkalization. Using cyclic voltammetry (CV) for surface characterization and chronopotentiometry to monitor potential transients under constant current, the study demonstrates that HER on Bi(111) is a diffusion-controlled process that is highly sensitive to proton availability. Experimental data analysis revealed that the unified diffusion coefficient (D) decreases with increasing bulk pH, a trend consistent with the Grotthuss mechanism, while the cathodic charge transfer coefficient (αc) increases from approximately 0.74 at pH 2.0 to 0.9 at pH 3.0, suggesting improved electron transfer kinetics in less acidic environments. Ultimately, the research confirms that while Bismuth (111) is an ineffective HER catalyst compared to noble metals due to its weak hydrogen binding and slow Volmer adsorption steps, the proposed mathematical model accurately determines critical kinetic parameters and benchmarks catalytic activity by identifying the exact point of surface pH shifts.