The formation of porosity within nanoparticles via dealloying is notably constrained by the dimensions of the precursor particles, a limitation stemming from the surface kinetic processes occurring during dealloying. In this study, we present a straightforward methodology, specifically tailored for fabricating diminutive nanoporous alloy nanoparticles, originating from their small-sized precursor counterparts. We initiated our research with precursor PtNi alloy nanoparticles, which possess an average diameter of 9 nm. By incorporating an extrinsic metal, Ir, known for its slower surface diffusion on the nanoparticle surface, we successfully modulated the surface migration velocity of Pt during the dealloying process of the PtNi alloy nanoparticles. This precise manipulation led to the formation of an abundantly complex nanoporous structure on diminutive PtNi nanoparticles. Owing to their enhanced high surface area-to-volume ratio and the synergistic alloy effect, electrochemical tests revealed that the Ir-coated diminutive nanoporous PtNi nanoparticles exhibit superior electrocatalytic activities towards oxygen reduction and formic acid oxidation reactions. Furthermore, the presence of Ir on the surface effectively suppresses the surface diffusion rate of Pt, thereby significantly inhibiting the coarsening evolution of the porous metallic structure. This intervention ensures the long-term preservation of both structural integrity and catalytic stability.

The oxygen evolution reaction (OER) represents an anodic reaction for a variety of sustainable energy conversion and storage technologies, such as hydrogen production, CO₂ reduction, etc. To realize the large-scale implementation of these technologies, the sluggish kinetics of the OER resulting from multi-step proton/electron transfer and occurring at the gas–liquid–solid triple-phase boundary needs to be accelerated. Manganese oxide-based (MnO_x) materials, especially MnO₂, have become promising non-precious metal electrocatalysts for the OER under acidic conditions due to the good trade-off between catalytic activity and stability. This paper reviews the recent progress of MnO₂-based materials to catalyze the OER through either the traditional adsorbent formation mechanism (AEM) or the emerging lattice-oxygen-mediated mechanism (LOM). Pure manganese dioxide OER catalysts with different crystalline structures and morphologies are summarized, while MnO₂-based composite structures are also discussed, and the application of MnO₂-based catalysts in PEMWEs is summarized. Critical challenges and future research directions are presented to hopefully help future research.