Grain boundary enriched anisotropic gold nanoparticles (GNP-50, GNP-75, and GNP-150) show remarkable heterogeneous catalytic activity with a greater TON (2.86 × 10⁷min⁻¹) and TOF (∼8000 h⁻¹) for the chemical reduction of 4-nitrophenol and enhanced electrochemical reduction of H₂O₂ with a remarkably high peak current (i_P) and heterogeneous rate constant (k₀) along with a substantially low charge transfer resistance (R_CT).

Abstract

This study reports the catalytic activity of our synthesized differentially-branched gold nanoparticles (GNPs), namely spherical (GNP-50), branched (GNP-75), and quasi-branched (GNP-150) GNPs. By looking toward the dominating role of stacking fault (SF) and grain boundary (GB) defects in catalysis compared to other 2D crystal defects, out of three differentially-branched and negatively charged GNPs, GNP-75 with the highest GB density shows the best catalytic activity. We have compared their chemical catalysis efficiency by studying the reduction of 4-nitrophenol in terms of turnover number (TON) and turnover frequency (TOF). The obtained result shows an enhancement in catalytic activity, in terms of both TON and TOF, by sixteen-fold and four-fold for GNP-75 compared to GNP-50 and GNP-150, respectively. On the other hand, the superior catalytic activity of GNP-75 is further established by studying the electrocatalytic reduction of H₂O₂ and comparing it with GNP-50 and GNP-150 in terms of current density and charge transfer resistance. This study uniquely highlights the specific role of GB defect-induced strain in controlling the heterogeneous catalytic reaction rate.