Atomic Arrangement Engineering of Metallic Nanocrystals for Energy-Conversion Electrocatalysis

The growing demand of human beings for energy calls for sustainable energy-conversion techniques (e.g., fuel cells and water splitting), and it is a key to developing advanced electrocatalysts, primarily composed of metallic nanocrystals (NCs), for the corresponding electrocatalytic reactions. Electrocatalytic performance of NC catalysts can often be tuned by controlling composition, size, and surface morphology. In recent reports, the activity of NCs can be greatly enhanced by precisely engineering the atomic position and arrangement within NC (atomic arrangement engineering [AAE]). In this review, we demonstrate how the microstructures, including crystal phase, atomic arrangement, and strain coupling, determine the surface electronic structures of metallic NCs and therefore the catalytic performance. Based on the introduction of structure transformation process from thermodynamic and kinetic perspectives, we discuss key factors to precisely control the structure of NCs. We then summarize two major AAE approaches including atomic ordering and planar stacking. Taking PtFe NC catalyst as an example, after transforming disordered PtFe to fully ordered PtFe NCs, it delivers much better activity and durability in fuel cell because of optimal strain effect and strong 3d and 5d electron interaction. It is vital to prepare NCs with both desired morphology and controlled phase in moderate conditions at a large scale. Further attention should be paid on bridging the gap between laboratory studies and industrial applications. AAE of NCs can be also applied to other important fields including electronics, magnetics, sensoring, and medicine.