To combat the global problem of CO2 emissions, H2 is the desired energy vector for the transition to environmentally benign fuel cell power. Water electrolysis (WE) is the major technology for sustainable H2 production. Despite the use of renewable solar and wind power as sources of electricity, one of the main barriers for the widespread implementation of WE is the scarcity and high cost of platinum-group metals (PGMs) that are used to catalyze the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER). Hence, the critical PGM-based catalysts must be replaced with more sustainable alternatives for WE technologies to become commercially viable. This critical review describes the state-of-the-art PGM-free materials used in the WE application. Several emerging classes of HER and OER catalysts are reviewed and detailed structureproperty correlations are comprehensively summarized. The influence of the crystallographic and electronic structures, morphology, and bulk and surface chemistry of the catalysts on the activity towards OER and HER is discussed.
Soft Materials used in heart valve research: A critical review
