Toward expanding the realm of high entropy materials to platinum group metals: A review

High entropy materials (HEMs) have emerged as a new class of materials with exceptional scientific and technological potential. Since discovery of high entropy alloys (HEAs) in 2004, the concept of high entropy has been enlarged to ceramic, sulfide, fluoride, and phosphide materials. Correspondingly, their nearly infinite compositional space has been expanded to refractories, lanthanides, and recently platinum group metals (PGMs). Among these types of alloys, PGM-based HEM nanoparticles (HEM-NPs) are of great scientific interest because of the ability to continuously tailor their properties by tuning the ratio of noble to non-noble metal species. Besides, the functional properties of bulk HEAs such as shape memory effect, magnetocaloric, and superconductivity are attracting more and more attentions. In this review, we discuss the progress in the PGM-based HEMs focusing on catalytic performance of nano-particles and functional properties of bulk materials. We begin with the synthesis of HEM-NPs emphasizing on the ability of alloying immiscible elements into single phase NPs. Then, we summarize the reported catalytic/electrocatalytic applications of HEM-NPs for different types of reactions, including CO2/CO reduction reactions, CO oxidation, methanol oxidation, oxygen reduction reaction and electrochemical water splitting. We present a case-by-case discussion to clarify how various metal species can play distinct role in chemically complex structure of HEM-NPs under different reaction conditions. We further try to give a picture of the current state of shape memory, magnetocaloric, and superconductivity effects in the bulk PGM-based HEAs. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

High entropy materials (HEMs), including high entropy alloys (HEAs) and other types of high entropy materials, have exceptional scientific and technological potential. PGM-based HEM nanoparticles have advantages in continuously adjusting properties, while functional properties like shape memory effect, magnetocaloric, and superconductivity in bulk materials also attract attention.