The increasing world population and the need to improve quality of life for a large percentage of human beings are the driving forces for the search for sustainable energy production systems, alternative to fossil fuel combustion. Among the various types of alternative energy production technologies, solid oxide fuel cells (SOFCs) operating at intermediate temperatures (400–700 °C) show the advantage of possible use both for stationary and mobile energy production. To reach the goal of reducing the SOFC operating temperature, proton-conducting oxides are gaining wide interest as electrolyte materials. This critical review provides a broad overview of the most recent progresses obtained tailoring the properties of proton-conducting oxides for fuel cell applications, analyzing and comparing the different strategies proposed to match high-proton conductivity with good chemical stability (170 references).

Materials challenges toward proton-conducting oxide fuel cells: a critical review

Water vapor solubility and electrochemical characterization of the high temperature proton conductor BaZr0.9Y0.1O2.95

Space–charge theory applied to the grain boundary impedance of proton conducting BaZr0.9Y0.1O3 − δ

Carbon nanotube (CNT) supported Pt nanoparticle catalysts have been prepared by spontaneous reduction of PtCl6(2-) ion as a result of direct redox reactions between PtCl6(2-) and oxygen-containing functional groups at defect sites of CNTs, which were introduced by chemical and electrochemical oxidation treatment of CNTs. The electrocatalytic properties of as-prepared Pt-CNT catalysts for methanol oxidation were investigated by chronopotentiometry and cyclic voltammetry. Compared with Pt catalysts prepared by hydrogen reduction and electrochemical deposition methods, Pt catalysts synthesized by functional CNT defects show excellent antipoisoning ability and long-term cycle stability.

Platinum Catalysts Prepared with Functional Carbon Nanotube Defects and Its Improved Catalytic Performance for Methanol Oxidation

Oxide-based protonic conductors: point defects and transport properties

A preparation method for catalyst layers of platinum nanoparticles, as used in direct methanol fuel cells, based
 on pulsed electrochemical deposition within the three-phase boundary regions responsible for electrochemical reactions, was developed. A platinum precursor was brought into a carbon–Nafion layer and platinum was deposited
 in situ on the carbon surface. The size, size distribution and crystallinity of the deposited catalyst particles were determined by means of high-resolution transmission electron microscopy and X-ray diffraction measurements.
 The electrochemically active surface area of the deposited catalyst
 material was investigated by cyclic voltammetry, analysing the Pt–H oxidation peak.

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Synthesis and characterization of catalyst layers for direct methanol fuel cell applications

BaZr0.85Me0.15O2.925 (Me=Y, In and Ga): crystal growth, high-resolution transmission electron microscopy, high-temperature X-ray diffraction and neutron scattering experiments

Proton conducting Ba3Ca1.18Nb1.82O8.73–H2O: pressure–compositions isotherms in terms of Fermi-Dirac statistics, concentration and fuel-cell measurements, and impedance spectroscopy

Films of SrYb 0.05 Zr 0.095 O 2.975 were prepared by sol-gel processing. Water vapour pressure/hydrogen composition isotherms were recorded ex-situ comprising pressures between 0 and 84.5 kPa and temperatures between 873 and 1073 K. Nuclear Resonance Reaction Analysis (NRRA) was used to determine the hydrogen concentration and, in addition, depth profiles of hydrogen concentration. The chemical potential of interstitial hydrogen in oxides could be determined; from its temperature dependence thermodynamical constants were calculated. We observe two hydrogen fractions with a site energy difference of 20 kJ/mol. A size effect of the thermodynamic properties is observed below a thickness of 350 nm: nanofilms exhibit higher solubility than bulk material.

Pressure/composition isotherms of proton conducting SrYb0.05Zr0.95O2.975/H2O by means of nuclear resonance reaction analysis

The dynamic production of green energy requires capable mediate storage solutions, often in the form of large batteries. Here, a Vanadium Redox Flow Battery is used to collect solar panels’ energy and, later, power electric vehicles. Since the balance of the chemical liquids inside the battery can change over multiple loading cycles, a system for predictive monitoring is needed. This paper presents the project “hILDe - Novel, cost-effective and highly accurate indication of imbalance and state of charge of vanadium redox flow batteries using AI-assisted detection of specific colors”, which features an absorbance sensor for chemical liquids and an AI-empowered monitoring system to interpret and predict sensory data. The current progress in our lab scenario suggests that the deployment of our sensor and monitoring system enables an accurate and cost-efficient imbalance and state of charge sensor for Vanadium Redox Flow Batteries. In the future, the system will be tested in full-sized batteries to verify its scalability and commercial potential. 

B. Groß

Papers

Synthesis and characterization of catalyst layers for direct methanol fuel cell applications

BaZr0.85Me0.15O2.925 (Me=Y, In and Ga): crystal growth, high-resolution transmission electron microscopy, high-temperature X-ray diffraction and neutron scattering experiments

Proton conducting Ba3Ca1.18Nb1.82O8.73–H2O: pressure–compositions isotherms in terms of Fermi-Dirac statistics, concentration and fuel-cell measurements, and impedance spectroscopy

Pressure/composition isotherms of proton conducting SrYb0.05Zr0.95O2.975/H2O by means of nuclear resonance reaction analysis

hILDe: AI-Empowered Monitoring System for Vanadium Redox Flow Batteries