Gold Nanoparticles for CO₂ Electroreduction: An Optimum Defined by Size and Shape

Understanding the size-dependent behavior of nanoparticles is crucial for optimizing catalytic performance. We investigate the differences in selectivity of size-selected gold nanoparticles for CO₂ electroreduction with sizes ranging from 1.5 to 6.5 nm. Our findings reveal an optimal size of approximately 3 nm that maximizes selectivity toward CO, exhibiting up to 60% Faradaic efficiency at low potentials. High-resolution transmission electron microscopy reveals different shapes for the particles and suggests that multiply twinned nanoparticles are favorable for CO₂ reduction to CO. Our analysis shows that twin boundaries pin 8-fold coordinated surface sites and in turn suggests that a variation of size and shape to optimize the abundance of 8-fold coordinated sites is a viable path for optimizing the CO₂ electrocatalytic reduction to CO. This work contributes to the advancement of nanocatalyst design for achieving tunable selectivity for CO₂ conversion into valuable products.