An overview of recent advances in Pt and Pd-based materials: From design strategies to reaction mechanisms

Due to the growing demand for energy and the threat of environmental problems, advanced energy storage and conversion technologies have attracted considerable attention as alternatives to conventional technologies. Platinum group metals (PGMs), especially platinum (Pt) and palladium (Pd)-based materials, have shown remarkable potential for storage and oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) due to their high catalytic activity, electrochemically active sites, surface area, permeability, charge transfer resistance, electrical conductivity, and corrosion resistance. However, the scarcity and high price of PGMs hinder their practical application in the commercial sector. Moreover, the availability of PGM electrodes/catalysts with high activity and stable electrochemical performance is critical for developing long-term and cost-effective energy storage/conversion technologies. Therefore, this review focuses on the recent advances in the synthesis strategies for single-atom, alloy-based, and composite Pt and Pd electrocatalysts, their structure-performance relationships, and applications in various energy sectors. The challenges of material stability, cost reduction, and the engineering of highly efficient catalysts, as well as future directions for enhancing their performance in conversion and energy storage technologies such as fuel-cells, metal-air batteries, supercapacitors, hydrogen storage and dye-sensitized solar cells are discussed.