Search

Since the 1990s, the advent of lithium-ion batteries has revolutionized energy storage in compact, high-density applications ranging from personal devices to passenger automobiles.Over the past 5 years, they have become crucial to making electrical grids resilient to weather anomalies. In this context, we will discuss nascent chemistry and system design around two energy storage/conversion systems: direct ammonia fuel cells (DAFCs), and membrane-less redox-flow batteries (RFBs). Both systems share a common layout and utilize the membrane-electrode assembly (MEA), which sandwiches the anode and cathode electrodes with aselective ion-exchange membrane.DAFCs operate as an open system, where ammonia and oxygen streams are converted into dinitrogen and water within the MEA while generating electricity for external loads. While ammonia offers logistical advantages over hydrogen, it presents a challenge in terms of the scarcity of efficient electrocatalysts for the sluggish 6e- NH3 oxidation. Our work emerges from the fundamental necessity for developing these electrocatalysts for protic conditions. We have found a molecular Ru complex that catalyzes rapid NH3 oxidation in aqueous conditions, demonstrating high selectivity for N2 – hitherto unprecedented among molecular electrocatalysts under aqueous conditions.Shifting focus to the membrane component, we will describe our efforts to improve membrane-less RFBs. RFBs employ the MEAs in a closed system, with anolyte and catholyte solutions containing redox active compounds circulating across the anode and cathode during operation. The ion-selective membrane in typical RFBs prevents self-discharge by separating the anolyte and catholyte, constituting a significant portion of the MEA cost. We will explore the shortcomings on previous attempts at biphasic membrane-less RFBs and explain a straightforward modification to the cell layout that overcomes interfacial self-discharge in these biphasic cells, elevating their Coulombic efficiency to >99%. In scaling up these cells,we will peek at ion transfer kinetics across liquid-liquid interfaces.

Understanding of the protonic defect transport mechanism in Ba(Ce,Zr)O3 perovskite oxides and defining the appropriate temperature range for ionic conductivity are fundamental to material design and application as electrolytes for solid oxide fuels and electrolyzer cells, isotopic separation membranes, and hydrogen sensors. Structural features of the material, and lattice distortions and proton diffusion are key factors that define the protonic conduction. The crystal structure of protonated and deuterated BaCe0.4Zr0.4Y0.2O3-? (BCZY) perovskite and its correlation with protonic transport was studied by in situ neutron powder diffraction (NPD) and complementary thermogravimetry (TG), quasi-elastic neutron scattering (QENS) and isotope exchange depth profiling (IEDP) techniques. A second order phase transition from rhombohedral to cubic symmetry takes place at intermediate temperatures (400-600 °C). Dynamic measurements of NPD allowed the detection of the temperature of the phase transition for BCZY at around 520 °C. Crystallographic and microstructural parameters, including deuterium occupancy and anisotropic thermal parameters, were determined from high resolution NPD data. The deuterium (and oxygen) occupancy for pre-hydrated BCZY was at its maximum at low temperature and decreased at temperatures greater than 400 °C, even through the phase transition and beyond 600 °C. By contrast, proton diffusion increased with temperature above the phase transition. The combination of both effects, i.e., deuterium content and diffusion coefficient, explains the previous results showing that the proton conductivity dominates the ionic conductivity over the oxygen vacancy mechanism until 600 °C. The phase transition is mainly related to oxygen sublattice relaxation and does not impact the protonic transport mechanism.

Water management by gas diffusion electrodes is a fundamental aspect of the performance of electrochemical cells. Herein, we introduce the characteristic constrictions size as a descriptor for microporous layers (MPL). This parameter is calculated by volumetric analysis of focused ion beam nanotomography and compared to mercury intrusion porosimetry measurements.

Rational design of catalysts by tailoring specific surface sites with different elements could result in catalysts with high activity, selectivity and stability. In this work, we show that *CO on-top and O* on-top adsorption energies are good descriptors for catalysis of the CO oxidation reaction (COOR) on pure metals and binary alloys. The observed Brønsted-Evans-Polanyi (BEP) and scaling relations for COOR on different surfaces are incorporated into a predictive model that uses the binding strength of the four adjacent metal atoms making up the active site for COOR catalysis to estimate reaction and activation energies. The model is used to screen 234 multi-metallic catalyst candidates made by combining Ru, Pt, Pd, Cu and Au at these four sites. The screening and subsequent calculations suggest that Ru-Cu-Au and Ru-Pt-Cu alloys are good catalysts for COOR. Our study shows that it is possible to use information from pure metals and binary alloys to predict the catalytic behavior of more complex alloys, and hereby reduce the computational cost of identifying new catalyst candidates for COOR.

Hydrogen is emerging as one of the most promising energy carriers for a decarbonised global energy system. Transportation and storage of hydrogen are critical to its large-scale adoption and to these ends liquid hydrogen is being widely considered. The liquefaction and storage processes must, however, be both safe and efficient for liquid hydrogen to be viable as an energy carrier. Identifying the most promising liquefaction processes and associated transport and storage technologies is therefore crucial; these need to be considered in terms of a range of interconnected parameters ranging from energy consumption and appropriate materials usage to considerations of unique liquid-hydrogen physics (in the form of ortho–para hydrogen conversion) and boil-off gas handling. This study presents the current state of liquid hydrogen technology across the entire value chain whilst detailing both the relevant underpinning science (e.g. the quantum behaviour of hydrogen at cryogenic temperatures) and current liquefaction process routes including relevant unit operation design and efficiency. Cognisant of the challenges associated with a projected hydrogen liquefaction plant capacity scale-up from the current 32 tonnes per day to greater than 100 tonnes per day to meet projected hydrogen demand, this study also reflects on the next-generation of liquid-hydrogen technologies and the scientific research and development priorities needed to enable them.

Poly(phenylene sulfide benzimidazole) has been synthesized and tested as a potential material for high-temperature proton transport. A high content of sulfide bonds has been implemented in the polymer chains to endow a high antioxidant capacity and, in combination with bulky benzimidazole pendant units, to significantly suppress crystallinity and thereby improve the solubility in highly polar aprotic solvents. The amorphous polymer has high thermal stability and high glass transition temperature (Tg). Freestanding, insoluble, and robust membranes were obtained via thermal cross-linking of the benzimidazole moieties with octa-glycidyl polyhedral oligomeric silsesquioxane (g-POSS). The series of hybrid networks (cPPSBi_X, with X being the g-POSS content wt %) showed excellent oxidative stability, with cPPSBi_15 having weight loss lower than 5% after 264 h in Fenton's reagent at 80 °C. Elastic moduli as high as 868 MPa with reduced strain at break (1.8%) were obtained. After doping the membranes with phosphoric acid, proton conductivity in the range of 2.3 × 10-2 S cm-1 at 180 °C was obtained, and the membranes show a stress at break of 2.3 MPa. Dimensional and mechanical stability were maintained also at high doping levels thanks to the inclusion of g-POSS which provides the resulting hybrid networks with increased free volume and high cross-link density.

Reversible solid oxide cells (rSOC) can convert excess electricity to valuable fuels in electrolysis cell mode (SOEC) and reverse the reaction in fuel cell mode (SOFC). In this work, a five - cell rSOC short stack, integrating fuel electrode (Ni-YSZ) supported solid oxide cells (Ni-YSZ parallel to YSZ vertical bar CGO parallel to LSC-CGO) with an active area of 100 cm(2), is tested for cyclic durability. The fuel electrode gases of H-2/N-2:50/50 and H-2/H2O:20/80 in SOFC and SOEC mode, respectively, are used during the 35 reversible operations. The voltage degradation of the rSOC is 1.64% kh(-1) and 0.65% kh(-1) in SOFC and SOEC mode, respectively, with fuel and steam utilisation of 52%. The post-cycle steady-state SOEC degradation of 0.74% kh(-1) suggests improved lifetime during rSOC conditions. The distribution of relaxation times (DRT) analysis suggests charge transfer through the fuel electrode is responsible for the observed degradation. (C) 2022 The Author(s). Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.

Fuel cells recombine water from H-2 and O-2 thereby can power, for example, cars or houses with no direct carbon emission. In anion-exchange membrane fuel cells (AEMFCs), to reach high power densities, operating at high pH is an alternative to using large volumes of noble metals catalysts at the cathode, where the oxygen-reduction reaction occurs. However, the sluggish kinetics of the hydrogen-oxidation reaction (HOR) hinders upscaling despite promising catalysts. Here, the authors observe an unexpected ingress of B into Pd nanocatalysts synthesized by wet-chemistry, gaining control over this B-doping, and report on its influence on the HOR activity in alkaline conditions. They rationalize their findings using ab initio calculations of both H- and OH-adsorption on B-doped Pd. Using this "impurity engineering" approach, they thus design Pt-free catalysts as required in electrochemical energy conversion devices, for example, next generations of AEMFCs, that satisfy the economic and environmental constraints, that is, reasonable operating costs and long-term stability, to enable the "hydrogen economy."

There is currently a disconnect between the high electrocatalyst oxygen reduction reaction (ORR) performance measured ex situ, using the rotating disc electrode (RDE), and the in situ membrane electrode assembly (MEA) performance. The disconnect in the electrocatalyst performance raises questions both about the pitfalls of the RDE technique at extrapolating the performance to higher overpotentials and how to improve the in situ catalyst layer performance to meet ambitious fuel cell targets. This work aims to bridge the gap by measuring the ORR ex situ performance under high mass transport conditions, at high overpotentials, using the floating electrode (FE) technique. Here, we determine the performance of three Pt/C electrocatalysts using the FE in 1 M HClO4 and 1 M H2SO4 to show that the MEA activities measured at 80 °C, 150 kPag were substantially lower than the room temperature and pressure performance of the same catalyst in 1 M HClO4 using the RDE and FE methods and also lower than the FE in 1 M H2SO4, implying MEA limitations are not purely due to sulfonate adsorption from the Nafion. Finally, FE and MEA data was modeled which obtained jo values on the FE (oxide free conditions) which were 4–6× larger, at 11–26 μA cm–2, than those measured on the MEA. The difference is interpreted as due to better water removal in the FE system. This work shows that MEA catalyst layers are vastly underutilized, due to poor water transport, and current densities equivalent to 10–16 A cm–2 at 0.65 V for 400 μgPt cm–2 (25–40 A mg–1) are achievable, whereas the current mass activity of MEAs is

Knowledge of the performance of microbial electrolysis cells under a wide range of operating conditions is crucial to achieve high production efficiencies. Characterizing this performance in an experiment, however, is challenging due to either the long measurement times of steady-state procedures or the transient errors of dynamic procedures. Moreover, wide parallelization of the measurements is not feasible due to the high measurement equipment cost per channel. Hence, to speedup this characterization and to facilitate low-cost, yet widely parallel measurements, this paper presents a novel rapid polarization curve measurement procedure with a dynamic measurement resolution that runs on a custom six-channel potentiostat with a current-driven topology. As case study, the procedure is used to rapidly assess the impact of altering pH values on a microbial electrolysis cell that produces H2. A $\times 2$ – $\times 12$ speedup could be obtained in comparison with the state-of-the-art, depending on the characterization resolution (16–128 levels). On top of this speedup, measurements can be parallelized up to $6\times $ on the presented, affordable—42$-per-channel—potentiostat.

Perovskites have been widely studied for electrocatalysis due to the exceptional activity they exhibit for surface-mediated redox reactions. To date, descriptors based on density functional theory calculations or experimental measurements have assumed a bulk-like configuration for the surfaces of these oxides. Herein, we probed an initial exposed surface and the screened subsurface of LaMnO3 particles, demonstrating that their augmented activity toward the oxygen reduction reaction (ORR) can be related to a spontaneous surface reconstruction. Our approach involves high energy resolution electron energy loss spectroscopy for the fine structure probing of oxygen and manganese ionization edges under electron beam conditions that leave the structure unaffected. Atomic multiplet and density functional theory calculations were used to compute the theoretical energy loss spectra for comparison to the experimental data, allowing to quantitatively demonstrate that the particle surface layers are La-deficient. This deficiency is linked to equivalent tetrahedral Mn2+ sites at the reconstructed surface, leading to the coexistence of +3 and +2 oxidation states of Mn at the surface layers. This electronic and structural configuration of the as-synthesized particles is indirectly linked to strong adsorption pathways that promote the ORR on LaMnO3, and thus, it could prove to be a valuable design feature in the engineering of catalytic surfaces.

The performance of glucose enzyme electrodes, consisting of crosslinked flavin adenine dinucleotide glucose dehydrogenase (FADGDH), an osmium redox polymer and multi-walled carbon nanotubes on graphite electrodes, was tested in phosphate buffered saline, artificial plasma and the individual components of artificial plasma to assess the effect of each component on current response and operational stability of the response to better understand the decrease in electrode performance observed in blood. Electrodes tested in artificial plasma show a significant decrease in current response in 5 mM glucose, and operational stability of the response in 100 mM glucose, compared to electrodes tested in buffer. The lowest current response for the enzyme electrodes was observed in the presence of physiological level of uric acid although the largest alteration to enzyme affinity, as estimated from the apparent Michaelis-Menten constant, occurred upon addition of physiological level of sodium bicarbonate. The operational stability observed in the presence of uric acid was the lowest of all components tested, with only 46% of initial current response after 12 h, and was comparable to the 27% of current remaining after 12 h for electrodes operating in artificial plasma. The effect of uric acid on glucose oxidation by enzyme electrodes prepared using both glucose oxidase (GOx) and a recombinant cellobiose dehydrogenase (CDH) was assessed. The maximum current decreased for both FADGDH and GOx enzyme electrodes in the presence of uric acid, with no significant change to the enzyme affinity, suggesting non-competitive inhibition. The CDH based electrodes provided highest stability of current signal in buffer, with 86% of the initial signal present after 12 h, but display significant change in enzyme affinity, maximum current and operational stability, dropping to only 33%, in the presence of uric acid. In contrast the operational stability of the GOx-based enzyme electrodes was unaffected by the presence of physiological level of uric acid. As uric acid and sodium bicarbonate are present in blood, these results highlight the importance of enzyme selection for in vivo biosensing and biofuel cell applications. Further work is required to understand the mechanism of uric acid inhibition on each of the enzymes. (C) 2019 Elsevier Ltd. All rights reserved. R. Bennett acknowledges support through an NUI Galway College of Science fellowship and an Irish Research Council Postgraduate Scholarship (GOIPG/2016/505). Donation of recombinant CDH produced with financial support from the European Commission (“Bioenergy” PEOPLE-2013-ITN-607793) by Roland Ludwig (University of Boku) is gratefully acknowledged. peer-reviewed 2021-02-11

Active Pt-based catalysts at low temperature towards the preferential oxidation of carbon monoxide in hydrogen-rich stream reaction (CO-PROX) are of great importance for H-2-fueled fuel cells, but still remain a challenge. Herein, we propose a simple approach to synthesize a highly active Pt20Fe/CeO2 catalyst employing the borohydride reduction process. Transmission electronic microscopy revealed monodispersed 2.8 nm-Pt nanoparticles on CeO2, and the role of Fe species on the activity is discussed. The excellent CO conversion of 99.6% and CO2 selectivity of 92.3% carried out at ambient temperature meet the CO-PROX requirements for an adequate supply of hydrogen in fuel cell device. (C) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Negative emission technologies have recently received increasing attention due to climate change and global warming. One among them is bioenergy with carbon capture and storage (BECCS), but the capture process is very energy intensive. Here, a novel pathway is introduced, based on second-generation biofuels followed by carbon circulation in an indefinitely closed chain, effectively resulting in a sink. Instead of using an energy-intensive conventional CCS process, the application of an on-board solid oxide fuel cell (SOFC) running on biofuels in an electric vehicle (FCEV) could result in negative emissions by capturing a concentrated stream of CO2, which is readily stored in a second tank. A CO2 recovery system at the fuel station then takes the CO2 from the tank to be transported to storage locations or to be used for local applications such as CO2-based concrete curing and synthesis of e-fuels. Incorporating CO2 utilization technologies into the FCEVs-SOFC system can close the carbon loop, achieving carbon neutrality through feeding the CO2 in a reverse-logistic to a methanol plant. The methanol produced is also used in SOFCs, leading to an infinite repetition of this carbon cycle till a saturation stage is reached. It is determined this pathway will reach typical Cradle-to-Grave negative emissions of 0.515 ton CO2 per vehicle, and total negative CO2 emission of 138 Mt for all passenger cars in the EU is potentially achievable. All steps comprise known technologies with medium to high technology readiness level (TRL) levels, so principally this system can readily be applied in the mid-term.

This paper presents a novel, cost-effective approach to the fabrication of composite anion exchange membranes (AEMs). Hierarchical AEMs have been fabricated by coating a porous substrate with an interpenetrating polymer network (IPN) layer where poly(vinylpyrrolidone) (PVP) is immobilized in a crosslinked matrix. The IPN matrix was formed by UV initiated radical crosslinking of a mixture of acrylamide-based monomers and acrylic resins. The fabricated membranes have been compared with a commercial material (Fumatech FAP 450) in terms of ionic transport properties and performance in a vanadium redox flow battery (VRFB). Measures of area-specific resistance (ASR) and vanadium permeability for the proposed membranes demonstrated properties approaching the commercial benchmark. These properties could be tuned by changing the content of PVP in the IPN coating. Higher PVP/matrix ratios facilitate a higher water uptake of the coating layer and thus lower ASR (as low as 0.58 Ω.cm2). On the contrary, lower PVP/matrix ratios allow to reduce the water uptake of the coating and hence decrease the vanadium permeability at the cost of a higher ASR (as high as 1.99 Ω.cm2). In VRFB testing the hierarchical membranes enabled to reach energy efficiency comparable with the commercial AEM (PVP_14-74.7%, FAP 450-72.7% at 80 mA.cm-2). ispartof: POLYMERS vol:13 issue:15 ispartof: location:Switzerland status: published

The intense demand for alternative energy has led to efforts to find highly efficient and stable electrocatalysts for the methanol oxidation reaction. For this purpose, herein, graphene oxide-based platinum-cobalt nanoparticles (Pt100−xCox@GO NPs) were synthesized in different ratios and the synthesized nanoparticles were used directly as an efficient electrocatalyst for methanol oxidation reaction (MOR). The characterizations for the determination of particle size and surface composition of nanoparticles were performed by transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The structure of the catalysts was detected as face-centered cubic and the dispersion of them on graphene oxide was homogenous (distributed narrowly (4.01 ± 0.51 nm)). Cyclic voltammetry (CV) and chronoamperometry (CA) was utilized for testing electrocatalytic activities of all prepared NPs for the methanol oxidation reaction. It was detected that the newly produced NPs were more active and stable than commercially existing Pt(0)/Co nanomaterial in methanol electro-oxidation in acidic media.

Mixed ionic-electronic conductors (MIECs) that display high oxide ion conductivity (σo ) and electronic conductivity (σe ) constitute an important family of electrocatalysts for a variety of applications including fuel cells and oxygen separation membranes. Often MIECs exhibit sufficient σe but inadequate σo . It has been a long-standing challenge to develop MIECs with both high σo and stability under device operation conditions. For example, the well-known perovskite oxide Ba0.5 Sr0.5 Co0.8 Fe0.2 O3- δ (BSCF) exhibits exceptional σo and electrocatalytic activity. The reactivity of BSCF with CO2 , however, limits its use in practical applications. Here, the perovskite oxide Bi0.15 Sr0.85 Co0.8 Fe0.2 O3- δ (BiSCF) is shown to exhibit not only exceptional bulk transport properties, with a σo among the highest for known MIECs, but also high CO2 tolerance. When used as an oxygen separation membrane, BiSCF displays high oxygen permeability comparable to that of BSCF and much higher stability under CO2 . The combination of high oxide transport properties and CO2 tolerance in a single-phase MIEC gives BiSCF a significant advantage over existing MIECs for practical applications.

Membranes with fast and selective ion transport are widely used for water purification and devices for energy conversion and storage including fuel cells, redox flow batteries and electrochemical reactors. However, it remains challenging to design cost-effective, easily processed ion-conductive membranes with well-defined pore architectures. Here, we report a new approach to designing membranes with narrow molecular-sized channels and hydrophilic functionality that enable fast transport of salt ions and high size-exclusion selectivity towards small organic molecules. These membranes, based on polymers of intrinsic microporosity containing Troger’s base or amidoxime groups, demonstrate that exquisite control over subnanometre pore structure, the introduction of hydrophilic functional groups and thickness control all play important roles in achieving fast ion transport combined with high molecular selectivity. These membranes enable aqueous organic flow batteries with high energy efficiency and high capacity retention, suggesting their utility for a variety of energy-related devices and water purification processes. Ion-selective membranes are widely used for water purification and electrochemical energy devices but designing their pore architectures is challenging. Membranes with narrow channels and hydrophilic functionality are shown to exhibit salt ions transport and selectivity towards small organic molecules.

Lack of suitable electron donors or acceptors is in many cases the key reason for pollutants to persist in the environment. Externally supplementation of electron donors or acceptors is often difficult to control and/or involves chemical additions with limited lifespan, residue formation or other adverse side effects. Microbial electrochemistry has evolved very fast in the past years - this field relates to the study of electrochemical interactions between microorganisms and solid-state electron donors or acceptors. Current can be supplied in such so-called bioelectrochemical systems (BESs) at low voltage to provide or extract electrons in a very precise manner. A plethora of metabolisms can be linked to electrical current now, from metals reductions to denitrification and dechlorination. In this perspective, we provide an overview of the emerging applications of BES and derived technologies towards the bioremediation field and outline how this approach can be game changing This work was funded through the European Union’s Horizon 2020project ELECTRA under grant agreement No. 826244 and National Natural Science Foundation of China (NSFC) (No. 31861133001,31861133002, 31861133003). S.P is a Serra Húnter Fellow (UdG-AG-575) and acknowledges the funding from the ICREA Acad emia award.LEQUiA has been recognized as consolidated research group by theCatalan Government with code 2017-SGR-1552. KR is supported by theGhent University special research fund under grant No. BOF19/GOA/026

A key prerequisite for the hydrogen economy is cost-effective renewable hydrogen supply. This paper provides a framework for the thermodynamic and economic assessment of solar hydrogen production from the high-temperature steam electrolysis (HTSE) route. A system configuration for the solar-driven steam electrolysis plant is proposed. The thermodynamic and economic analysis is done for varying temperature and current density conditions of the solid oxide electrolyzer powered by concentrated solar (CSP) and photovoltaic (PV) power plants. Based on the expected reductions in the cost of plant components, the levelized cost of hydrogen (LCOH2) for the 2030 scenario is evaluated. Conditions for the viability of this route are checked by comparing the results with the polymer electrolyte membrane electrolysis (PEME) process. The optimum energy efficiency of a PV driven process increases from 9.1% at 873 K, 1500 A/m(2) to 12.1% at 1273 K. 8000 A/m(2). For the electrolyzer operating at 873 K, the optimum LCOH2 of 22 $/kg is obtained at 6000 A/m(2). For the electrolyzer temperature of 1073 K, LCOH2 drops from 16 $/kg at 5000 A/m(2) to 12.1 $/kg at 10000 A/m(2). When compared to PEME, this route becomes viable beyond 973 K, 6000 A/m(2) for PV and 923 K, 3000 A/m(2) for CSP driven processes. With the current state of economics, this process is not competitive with the industrial steam methane reforming route. However, the cost target of 6-8 $/kg is achievable if the component costs reduce to 2030 level. Thus, the process has potential to be commercially viable and should be pursued further by creating prototype and pilot scale demonstrations. (C) 2018 Elsevier Ltd. All rights reserved.

Squaric acid (SA) has been investigated as a readily available organic anode material in rechargeable lithium batteries. To overcome both conductivity and dissolution problems related to organic compounds, SA was conformally coated with conductive polyaniline through a facile in situ chemical polymerization route. Polyaniline-coated SA exhibits a stable high capacity of 394 mAhg(-1) after 100 cycles at 100 mAg(-1) in lithium batteries. At 1 Ag-1 current density, polyaniline-coated SA (PANI-SA) shows long cycle life over 1000 cycles with 96.9% retention of initial reversible capacity. The reversible Li+ storage property of SA is revealed through ex situ NMR characterization.