Redox

About: Redox is a research topic. Over the lifetime, 26853 publications have been published within this topic receiving 862368 citations. The topic is also known as: reduction-oxidation & reduction-oxidation reaction.

Nickel ferrocyanide as a high-performance urea oxidation electrocatalyst

Abstract: Urea is often present in waste water but can be used in powering fuel cells and as an alternative oxidation substrate to water in an electrolyser. However, an insufficient mechanistic understanding and the lack of efficient catalysts for the urea oxidation reaction have hampered the development of such applications. Here we demonstrate that a nickel ferrocyanide (Ni2Fe(CN)6) catalyst supported on Ni foam can drive the urea oxidation reaction with a higher activity and better stability than those of conventional Ni-based catalysts. Our experimental and computational data suggest a urea oxidation reaction pathway different from most other Ni-based catalysts that comprise NiOOH derivatives as the catalytically active compound. Ni2Fe(CN)6 appears to be able to directly facilitate a two-stage reaction pathway that involves an intermediate ammonia production (on the Ni site) and its decomposition to N2 (on the Fe site). Owing to the different rate-determining steps with more favourable thermal/kinetic energetics, Ni2Fe(CN)6 achieves a 100 mA cm−2 anodic current density at a potential of 1.35 V (equal to an overpotential of 0.98 V). Urea oxidation could be a lower-energy alternative to water oxidation in hydrogen-producing electrolysers, but improved catalysts are required to facilitate the reaction. Geng et al. report nickel ferrocyanide as a promising catalyst and suggest that it operates via a different pathway to that of previous materials.

Development of Double-Perovskite Compounds as Cathode Materials for Low-Temperature Solid Oxide Fuel Cells

Abstract: A class of double-perovskite compounds display fast oxygen ion diffusion and high catalytic activity toward oxygen reduction while maintaining excellent compatibility with the electrolyte. The astoundingly extended stability of NdBa1−xCaxCo2O5+δ (NBCaCO) under both air and CO2-containing atmosphere is reported along with excellent electrochemical performance by only Ca doping into the A site of NdBaCo2O5+δ (NBCO). The enhanced stability can be ascribed to both the increased electron affinity of mobile oxygen species with Ca, determined through density functional theory calculations and the increased redox stability from the coulometric titration.

High energy density vanadium electrolyte solutions, methods of preparation thereof and all-vanadium redox cells and batteries containing high energy vanadium electrolyte solutions

Abstract: Disclosed is a method for preparing a high energy density (HED) electrolyte solution for use in an all-vanadium redox cells, a high energy density electrolyte solution, in particular an all-vanadium high energy density electrolyte solution, a redox cell, in particular an all-vanadium redox cell, comprising the high energy density electrolyte solution, a redox battery, in particular an all-vanadium redox battery, comprising the HED electrolyte solution, a process for recharging a discharged or partially discharged redox battery, in particular an all-vanadium redox battery, comprising the HED electrolyte solution, a process for the production of electricity from a charged redox battery, and in particular a charged all-vanadium redox battery, comprising the HED electrolyte, a redox battery/fuel cell and a process for the production of electricity from a redox battery/fuel cell. A method for stabilising an electrolyte solution for use in a redox cell, in particular for stabilising an electrolyte solution for use in an all-vanadium redox cell, a stabilised electrolyte solution, in particular an all-vanadium stabilised electrolyte solution, a redox cell, in particular an all-vanadium redox cell, comprising the stabilised electrolyte solution, a redox battery, in particular an all-vanadium redox battery, comprising the stabilised electrolyte solution, a process for recharging a discharged or partially discharged redox battery, in particular an all-vanadium redox battery, comprising the stabilised electrolyte solution, and a process for the production of electricity from a charged redox battery, and in particular a charged all-vanadium redox battery, comprising the stabilised electrolyte solution are disclosed. Also disclosed are a redox battery/fuel cell and a process for the production of electricity from a redox battery/fuel cell.

Electron transfer mechanisms between microorganisms and electrodes in bioelectrochemical systems

Abstract: Microbes have been shown to naturally form veritable electric grids in which different species acting as electron donors and others acting as electron acceptors cooperate. The uptake of electrons from cells adjacent to them is a mechanism used by microorganisms to gain energy for cell growth and maintenance. The external discharge of electrons in lieu of a terminal electron acceptor, and the reduction of external substrates to uphold certain metabolic processes, also plays a significant role in a variety of microbial environments. These vital microbial respiration events, viz. extracellular electron transfer to and from microorganisms, have attracted widespread attention in recent decades and have led to the development of fascinating research concerning microbial electrochemical sensors and bioelectrochemical systems for environmental and bioproduction applications involving different fuels and chemicals. In such systems, microorganisms use mainly either (1) indirect routes involving use of small redox-active organic molecules referred to as redox mediators, secreted by cells or added exogenously, (2) primary metabolites or other intermediates, or (3) direct modes involving physical contact in which naturally occurring outer-membrane c-type cytochromes shuttle electrons for the reduction or oxidation of electrodes. Electron transfer mechanisms play a role in maximizing the performance of microbe–electrode interaction-based systems and help very much in providing an understanding of how such systems operate. This review summarizes the mechanisms of electron transfer between bacteria and electrodes, at both the anode and the cathode, in bioelectrochemical systems. The use over the years of various electrochemical approaches and techniques, cyclic voltammetry in particular, for obtaining a better understanding of the microbial electrocatalysis and the electron transfer mechanisms involved is also described and exemplified.