Hollow nanostructures with controlled internal voids: Beyond simple surface area maximization of the electrocatalyst

Hollow nanostructured catalysts have traditionally been exploited to maximize surface area and intrinsic catalytic activity through structural and compositional engineering. Recent studies, however, reveal that hollow architectures play a more active role in shaping local reaction environments by regulating the transport and concentration of reactants, products, and reaction intermediates within confined spaces. This review summarizes recent advances in hollow electrocatalysts from the perspective of local concentration regulation at catalytic interfaces, highlighting how cavity-induced confinement effects influence reaction kinetics, selectivity, and stability. In this review, emerging design principles for tuning cavity size, shell thickness, and pore geometry to control mass transport and intermediate populations are discussed. Moreover, future opportunities and challenges, including confinement-driven catalyst design, operando characterization, and data-driven structural optimization, are outlined.