Bifunctional PGM-free metal organic framework-based electrocatalysts for alkaline electrolyzers: trends in the activity with different metal centers

Abstract

In order to solely rely on renewable and efficient energy sources, reliable energy storage and production systems are required. Hydrogen is considered an ideal solution since it can be produced...

Recent Progress and Viability of PGM-Free Catalysts for Hydrogen Evolution Reaction and Hydrogen Oxidation Reaction

“…14 In the context of HER catalysts, the development of MOFs is at its very beginning, with only a few active catalysts synthesized so far. 14,30 Unfortunately, none of the current MOFs are getting even close to the performance of Pt yet. There are also some stability issues, especially at extreme pH.…”

“…In electrolyzers, water molecules are electrochemically broken into oxygen at the anode and into hydrogen at the cathode . Both reactions are kinetically limited, especially the oxygen evolution reaction (OER). − The hydrogen evolution reaction (HER) is much more facile but still requires a catalyst to easily reach the necessary current densities. , Similar limitations are observed in fuel cells, which convert the chemical energy in hydrogen directly to electricity and water, where the oxygen reduction reaction (ORR) is considered to be more sluggish than the hydrogen oxidation reaction (HOR). Hence, most of the effort in recent years was invested in development of catalysts for the OER and ORR, while relatively very little was done for the HER and HOR.…”

Mixed-Metal Nickel–Iron Oxide Aerogels for Oxygen Evolution Reaction

“…The best way to achieve this is to use renewable energies in combination with electrochemical water electrolyzers, in which two distinct chemical reactions take place: the cathodic hydrogen evolution reaction (HER) − and the anodic oxygen evolution reaction (OER). − While both reactions require catalysts to be executed at high rates, the HER is considered to be relatively facile and takes place at low overpotentials relative to the OER, which requires higher overpotentials and precious metal catalyst loadings, and is hence considered the bottleneck reaction …”

Enhanced Oxygen Evolution Reaction with a Ternary Hybrid of Patronite–Carbon Nanotube-Reduced Graphene Oxide: A Synergy between Experiments and Theory

“…Therefore, cheaper and better alternatives should be developed that would not only help us achieve better catalytic efficacy but also improve the durability of the water-splitting device. In this regard, efforts have been devoted and various non-noble metal-based electrocatalysts have been developed. − However, the renewed interest in layered structured materials, after the revolutionary discovery of graphene, has led to the investigation of a wide range of analogous compounds that could replace the traditional catalysts made of precious metals. , Striking examples are transition metal chalcogenides (TMCs), which have peculiar electrocatalytic properties that have enabled them to impart substantial progress in the field of energy storage, energy conversion, sensing, electronics, etc. ,− However, during electrocatalysis, on applying anodic potential in an alkaline electrolyte, these TMCs get transferred to their corresponding oxides and oxyhydroxides. , This surface transformation induces a decrease in the inherent electrocatalytic performance of the TMCs as well as poor electrocatalytic stability. Being one of the promising compounds belonging to the TMC group, vanadium chalcogenides (primarily sulfide and selenides) have shown promising energy storage activities. − VS 4 , a prominent member of this group, contains two S 2 2– dimers with an unusual linear-chain structure.…”