Recent progress in ultrafine 3D Pd-based nanocubes with multiple structures for advanced fuel cells electrocatalysis

Recently, the noble metal-based, especially Pd-based, nanocatalysts have attracted great attention owing to their unique structural merits and high intrinsic activity resulting in enhancing the electrocatalytical efficiency for direct alcohol fuel cells (DAFC). Specially, among various Pd-based nanocatalysts, the 3D Pd-based nanocubes, endowed with large specific surface area, high structural stability, and favorable electric transmission capability have shown superb electrocatalytic performance for DAFC. So far, numerous researches, concerning the efficient synthesis, physicochemical characterization and electrocatalytic performance study about Pd-based nanocubes, have been widely reported. However, there is still lack of a comprehensive summary with regard to the universal synthesis strategies of Pd-based nanocubes and systematic analysis of the electrocatalytic ability enhancement. In this review, we firstly made an in-depth introduction of DAFC, mainly involving the two crucial half-reactions, namely, anodic alcohol oxidation reaction (AOR) and cathodic oxygen reduction reaction (ORR). Then, from the perspective of different physical morphologies of Pd-based nanocubes, the current synthesis pathways were generalized as the co-reduction approach, seed-mediated method, galvanic replacement and chemical etching, and meanwhile, the Pd-based nanocubes could also be classified as homogeneous, mesoporous, core–shell, hollow and concave nanocubes. In addition, some advanced strategies for electrocatalytic performance enhancement were further highlighted, which mainly included rich active sites, rational composition regulation, key facet control and efficient strain effect. Furthermore, the opportunities and challenges were also overviewed to provide guidance for the efficient synthesis and application of 3D Pd-based nanocubes in electrocatalytic field.