Alternating Potential Pulse Electrodeposition for Nanoparticles with Narrow Size Distribution and Improved Spatial Dispersion

Electrochemical methods for metal nanoparticle (MNP) electrodeposition offer precise control over particle formation without the need for harsh chemicals, extreme reaction conditions, high energy input, or the prolonged synthesis times associated with conventional approaches. Among electrochemical electrodeposition techniques, constant-potential amperometry is widely utilized, employing a single-step potential to reduce metal ions to solid metal at electrode surfaces, thereby producing MNPs. Although single-pulse electrodeposition provides improved control of MNP formation relative to bulk chemical synthesis, it often results in broad particle size distributions and poor spatial dispersion, particularly at longer deposition times. To address these limitations, herein we introduce an alternating potential pulse (APP) method as an approach to enhance particle size distribution, electrode surface coverage, and metal loading on carbon-based electrodes. The APP method was evaluated on two distinct carbon electrode platforms, namely, our nano-sized carbon ultramicroelectrode arrays (CUAs) and planar carbon macroelectrodes, using both gold (AuNPs) and silver nanoparticles (AgNPs). Overall, the APP method yielded higher counts of smaller, more narrowly distributed nanoparticles compared to the single-pulse approach. On CUAs, AuNP coverage increased from 70 ± 20% with the single 300 s pulse to 100% for 300 pulses of 1 s each. Macroelectrodes showed a similar improvement, with particle coverage increasing from 77 ± 7 to 186 ± 3 particles cm–2 under analogous conditions. Gold loading on CUAs likewise increased, rising from 90 ± 10 nmol with the single-pulse method to 310 ± 90 nmol using APP deposition. AgNP electrodeposition exhibited similar trends where Ag amounts on CUAs increased from 90 ± 20 nmol (one 60 s pulse) to 160 ± 10 nmol (six 10 s pulses), while macroelectrode Ag loading increased from 280 ± 30 to 400 ± 50 nmol over the same deposition period. We attribute these improvements to differences in diffusion-layer behavior at the electrode–solution interface induced by the unique APP potential-time waveform, wherein each deposition pulse renews metal-ion availability at the electrode surface and promotes more uniform nucleation. In summary, the APP method produced consistent enhancements across two distinct carbon-based electrode platforms and two different metals, demonstrating improved particle size distributions, surface coverage, and metal loading, and underscoring the versatility of the APP approach for MNP electrodeposition.