Unveiling the Excellent Electrocatalytic Activity of Grain-Boundary Enriched Anisotropic Pure Gold Nanostructures toward Hydrogen Evolution Reaction: A Combined Approach of Experiment and Theory

This report quantitatively investigates the role of grain-boundary and grain size in the excellent electrocatalytic activity of our recently synthesized shape-engineered (bud-shaped AuNP50 to bloom or flower-shaped AuNP75 to over-bloomed AuNP150) and differential grain-boundary enriched anisotropic flower-like gold nanostructures for the hydrogen evolution reaction (HER). All the synthesized anisotropic gold nanoparticles (AnGNPs) and especially the AuNP75 exhibit outstanding catalytic activities (in terms of both overpotential and turnover frequency) toward HER in different pH media compared to that of normal spherical-shaped gold nanoparticles (e.g., TSC-capped 25 nm AuNPsphs) in similar physical conditions. Further, the theoretical calculation based on density functional theory (DFT) nicely corroborates with the experimental findings and discloses the effective contribution of grain-boundaries toward the free energy of hydrogen adsorption (ΔGH*) and the position of the d-band center, which play a crucial role in their HER activities.