(Invited) Experimental and Theoretical Approaches to High Performance, Robust HER and Oxygen Evolution Reaction (OER) Electrocatalysts for Proton Exchange Membrane Based Water Electrolysis

Abstract

Water electrolysis is a well-known approach for the generation of clean and sustainable hydrogen via acid, alkaline and neutral mediated systems. Proton exchange membrane (PEM) based acid mediated water electrolysis is considered highly advantageous and one of the most reliable technologies for hydrogen generation and oxygen evolution among all other conventional hydrogen production approaches. However, the systems have yet to reach commercialization levels due to the use of highly expensive precious metal or platinum group metal (PGM) based electro-catalysts such as Pt, RuO2, and IrO2, all well-known for their excellent electrocatalytic activity and stability for both hydrogen and oxygen evolution reactions. There is a considerable need for the identification of non-noble metal based electrocatalysts for acid mediated water electrolysis. Over the years, we have focused our efforts at generation of novel transition metal based oxide solid solutions containing reduced amounts of noble metal oxide species. First principles density functional theoretical (DFT) based calculations largely aided by the use of the Vienna ab-initio simulation package (VASP) have been utilized to identify these novel solid solutions largely mimicking the electronic structure of the noble metal electrocatalyst systems. These theoretical calculations formed the basis for the identification of various reduced noble metal oxide containing solid solutions. These initial studies and theoretical understanding of the reaction mechanisms formed the basis for eventually identifying completely non-noble metal containing compositions. All of these systems display electrochemical activity comparable or even superior to the noble metal counterparts. Chronoamperometry studies in fact, indicate the systems to show even more robust electrocatalytic performance under primarily acid mediated conditions while being equally effective under basic and neutral pH conditions as well. This presentation will outline and summarize the collective efforts undertaken by my group over the years to identify low noble metal containing electrocatalysts as well as our recent findings of a completely non-noble metal based ternary transition metal oxide solid solution containing electronegative anion such as fluorine and its promising electrocatalytic response for water electrolysis and oxygen evolution reactions. Results of the studies conducted over the years will be presented while outlining future plans and strategies for the identification of such non-noble metal and non PGM based electrocatalysts for acid mediated water electrolysis.