Tag: fuel cells

What drives ions through polymer membranes

What drives ions through polymer membranes

Ion exchange membranes are needed in (photo)electrolysers, fuel cells and batteries to separate ions and enable the desired processes. Polymeric membranes such as synthetically produced compounds like NAFION are particularly efficient, but they cannot be degraded. A ban on the use of these “eternal chemicals” is currently under discussion in the European Union, and the development of suitable alternatives will be a major challenge. So, it is crucial to understand why NAFION and other established polymeric membranes work so well.

A team led by Dr. Marco Favaro of the HZB Institute for Solar Fuels has now investigated this using a special type of electrolysis cell. Here, the membrane sits on the outer wall and is in contact with both the liquid electrolyte and a gaseous external environment. It can act either as an anode or a cathode, depending on the polarity of the applied potential. This hybrid liquid-gas electrolyzer is considered particularly favorable for the electrochemical conversion of CO2 thanks to the higher CO2 concentrations that can be achieved in the gas phase, thereby overcoming the poor solubility of CO2 in aqueous solutions.

For the study, Favaro and his team used commercially available ion-exchange membranes in contact with a model electrolyte like sodium chloride (NaCl) in water. Water vapor was fed to the gas phase, with the partial pressure of water close to its vapor pressure at room temperature. To analyze the migration of sodium and chloride ions through the membrane, they used in situ ambient pressure hard X-ray photoelectron spectroscopy (AP-HAXPES) at the SpAnTeX end-station at the KMC-1 beamline of BESSY II.

“Indeed, we were expecting that the ion dynamics was determined, under applied potentials, by the electric fields generated between the anode and cathode of the electrolyzer, and that electromigration was therefore the main driver,” says Marco Favaro.

However, analysis of the data showed otherwise: electromigration hardly plays a role; the ions simply diffuse across the membrane. The data could be perfectly simulated numerically with a diffusion model. “Our conclusion is that ions move through the polymer membranes in these types of electrolyzers due to hopping mediated by the ionized functional groups present in the membranes. In addition, since water diffuses as well through the polymer, the ions are “dragged” as well” explains Favaro.

These results are exciting for a number of reasons: These types of electrolyzers are a way to convert CO2 into valuable chemicals that can otherwise only be obtained from fossil fuels. Understanding how these devices work helps on the way to decarbonize the economy. On the other hand, the ion-exchange membranes that are a key component of these cells are themselves problematic: the European Union may soon ban the use of persistent chemicals. Understanding the relevant drivers of such transport processes will help to develop new membrane materials that are both efficient, durable, and environmentally friendly. Favaro now intends to take this project forward at HIPOLE, the new Helmholtz Institute in Jena, which will focus on polymer materials for new energy technologies.

Read more in the Journal of Materials Chemistry A

Image: Membrane

Credit: HZB

Scientists uncover a different facet of fuel-cell chemistry

Scientists uncover a different facet of fuel-cell chemistry

Solid oxide fuel cells (SOFCs) are a promising technology for cleanly converting chemical energy to electrical energy. But their efficiency depends on the rate at which solids and gases interact at the devices’ electrode surfaces. Thus, to explore ways to improve SOFC efficiency, an international team led by researchers from Berkeley Lab studied a model electrode material in a new way—by exposing a different facet of its crystal structure to oxygen gas at operating pressures and temperatures.

“We began by asking questions like, could different reaction rates be achieved from the same material, just by changing which surface the oxygen reacts with?” said Lane Martin, a faculty scientist in Berkeley Lab’s Materials Sciences Division. “We wanted to examine how the atomic configuration at specific surfaces of these materials makes a difference when it comes to reacting with the oxygen gas.”

Thin films of a common SOFC cathode material, La0.8Sr0.2Co0.2Fe0.8O3 (LSCF), were epitaxially grown to expose a surface that was oriented along a diagonal crystallographic plane. Electrochemical measurements on this atypical surface yielded oxygen reaction rates up to three times faster than those measured on the usual horizontal plane.

To better understand the mechanisms underlying this improvement, the researchers used Advanced Light Source (ALS) Beamline 9.3.2 to perform ambient-pressure spectroscopy experiments at high temperatures and in varying pressures of oxygen. The results, combined with first-principles calculations, revealed that different crystallographic planes stabilize different surface chemistries, even though the bulk chemistry of the films is identical.

Read more on the ALS website

Image: A model SOFC cathode material adsorbs oxygen molecules (purple spheres) at vacancy sites, an important step in the electrochemical reaction taking place in fuel cells. Ambient-pressure experiments at the ALS allowed measurement of the surface chemical and electronic interactions at high temperature so that researchers could “see” the adsorption of oxygen at it happens. Light blue = La, dark blue = Sr, red = lattice O or O2 molecules, purple = adsorbed O2 molecules.

Credit: Abel Fernandez/UC Berkeley

Catalytic role of oxygen-containing groups on carbon electrodes

Catalytic role of oxygen-containing groups on carbon electrodes

The electrochemical reduction of oxygen plays a significant role in many critical applications such as gas sensors, hydrogen peroxide electrosynthesis, and electrochemical energy storage. Oxygen reduction reaction (ORR) drives the operation of fuel cells and metal-air batteries. The latter potentially can provide the highest specific energy among energy storage devices.

To increase the ORR efficiency, a catalyst immobilized on (or mixed with) conductive support is introduced to the positive electrode composition. Usually, porous sp2-carbon materials, like graphene, serve as such supporting materials. Its electronic configuration (sp2) provides the sufficient electric conductivity to the positive electrode. Nevertheless, ORR proceeds too slowly on the neat surface of ideal sp2-carbon in the absence of a catalyst.

The role of graphene imperfections (vacancies, impurity atoms, and functional groups) on catalyzing ORR (mainly in aqueous media) has been under intense investigation during the last decades. However, little is known about the effect of oxygen functionalization of carbon onORR in aprotic media (lacking the acidic protons). The interest in this process, especially in the presence of metal ions in the electrolyte, is relevant for various aprotic metal-oxygen batteries (lithium, sodium, magnesium, etc.) which are now considered as the most promising electrochemical power sources due to their outstanding theoretical performance. For such devices carbon electrodes are highly attractive due to their light weight and low cost, and the effect of carbon surface chemistry on the processes occurring upon battery operation is of great importance.

The present research shows for the first time that oxygenation of carbon electrode surface does not affect the rate of one-electron oxygen reduction in aprotic media. At the same time, in Li+-containing electrolytes, oxygen groups enhance both the rate of electrochemical Li2O2 formation and carbon electrode degradation due to faster oxidation by lithium superoxide (LiO2) intermediate yielding carbonate species as a product.

The research is led by scientists from Lomonosov Moscow State University and the Semenov Institute of Chemical Physics, in collaboration with Friedrich–Alexander–Universität Erlangen-Nürnberg, IFW Dresden, Saint Petersburg State University, Donostia International Physics Center and Massachusetts Institute of Technology. 

Read more on the ALBA website

Image: C 1s core level spectra of a) pristine and b) oxidized graphene electrodes before and after discharge. C) Model spectroelectrochemical Li-O2 cell. D) Evolution of C 1s components’ ratios upon discharge for pristine and oxidized graphene.

New versatile spectro-electrochemical cell

New versatile spectro-electrochemical cell

Equipment improves the investigation of materials for fuel cells, batteries and electrolysers

Fossil fuels are the main source of energy in the world. However, the search for clean, renewable, and cheap energy sources has intensified recently, especially with the growing consensus that the rise in the average temperature of the planet is caused by human action. In this context, electrochemical devices, which involve reactions for the transformation of chemical energy into electrical energy, appear as a viable option to fossil fuels.

Among those available are fuel cells and batteries, capable of converting the chemical energy of molecules into electrical energy and storing it, and electrolysers capable of converting low-cost molecules into more economically attractive molecules. Thus, to improve the performance of these electrochemical devices, it is essential to understand the processes that occur between their components, more precisely in the interaction between the electrodes and the electrolyte.

For this reason, researchers from the State University of Campinas (UNICAMP), in collaboration with researchers from the Brazilian Center for Research in Energy and Materials (CNPEM) and the Federal University of São Carlos (UFSCar), developed an electrochemical cell [1] with the objective to perform various types of in situ experiments. These experiments allow direct access to the dynamics of electrochemical reactions in real time and make it possible to understand the processes that occur in the system from an atomic and molecular point of view. Hence, it is possible to optimize the materials that are part of fuel cells, batteries and electrolysers mentioned, and also of devices such as supercapacitors and electrochemical sensors, among others.

Read more on the LNLS website

Image: Figure 1: A, B) Schematic drawings of the SEC: threaded lip (1); aperture for passing the radiation beam and, in the case of a photoelectrochemical experiment, to illuminate the electrode with a solar simulator or LEDs (2); window (3); O-rings (4, 5, 17); CE (6 16); SEC body – part 1 (7); chamber for the electrolyte, the CE and the RE (8); electrolyte inlet and outlet (9, 11, 13), WE inlet (10); RE inlet (12); RE (14); CE inlet (15); bolt (18); SEC body – part 2 (19); WE (20).

A step closer to smart catalysts for fuel generation

A step closer to smart catalysts for fuel generation

Researchers at the Universidade Federal do Rio Grande do Sul in Brazil in collaboration with the ALBA Synchrotron have performed the first detailed measurement of the strong metal-support interaction (SMSI) effect in Cu-Ni nanoparticles supported on cerium oxide.

A better understanding of this effect is essential for developing smart catalysts that are more selective, stable and sustainable. The quest for the best catalysts in industry has been a long one, but a new study by Universidade Federal do Rio Grande do Sul in Brazil, in collaboration with the ALBA Synchrotron, has come a step closer. For the first time, researchers have found evidence of what could be the origin of the SMSI effect in catalysts supported on cerium oxide.

Catalysts are used to increase the reaction rate of a given chemical reaction, and have applications in a wide variety of fields. In heterogeneous catalysis, the catalyst is usually composed of metal nanoparticles supported on metal oxides. Among them, CeO2-based catalysts have unique structural and atomic properties that make them suitable in the cutting-edge environmental industry of fuel cells and hydrogen. In this field, they are being explored as high-end photocatalytic reactors for the thermal splitting of water and carbon dioxide. However, what has been termed as the SMSI effect can undermine their desired properties.

>Read more on the ALBA website

Image: (extract, full picture here) Near Ambient Pressure – X-ray Photoemission Spectroscopy allowed the identification of the chemical components of the nanoparticles in situ.

Real-time characterisation of a new miniature-honeycomb fuel cell

Real-time characterisation of a new miniature-honeycomb fuel cell

A team from Imperial College has designed a miniature ceramic solid oxide fuel cell with excellent properties and together with scientists from the University College London, the company Finden and the ESRF, they characterised the cell as it works on beamline ID15A, confirming the great performances of the new device.

Ceramic fuel cells are considered as one of the most promising technologies for sustainable energy generation thanks to their interesting features, such as higher efficiency compared to conventional combustion-based power plants, high operating temperatures (600 – 1000 °C) that generate high-grade waste heat, and superior fuel flexibility that allows the direct utilization of hydrocarbons.

To date, ceramic fuel cells are used in a wide range of applications, including stationary power supply, combined heat and power system (CHP), auxiliary power units (APU), etc., and will continue receiving attention as shale gas and biofuels are becoming the premium fuel choices thanks to their low carbon footprint.

>Read more on the European Synchrotron website

Image: Micro-computed tomography and X-ray diffraction computed tomography images. XRD-CT maps of LSM (green), YSZ (red) and NiO (blue) have been overlaid on top of a micro-CT image collected at the same z position. The scale bar corresponds to 0.5 mm.
Credit: Tao Li.

Illuminating nanoparticle growth with X-rays

Illuminating nanoparticle growth with X-rays

Ultrabright x-rays at NSLS-II reveal key details of catalyst growth for more efficient hydrogen fuel cells

Hydrogen fuel cells are a promising technology for producing clean and renewable energy, but the cost and activity of their cathode materials is a major challenge for commercialization. Many fuel cells require expensive platinum-based catalysts—substances that initiate and speed up chemical reactions—to help convert renewable fuels into electrical energy. To make hydrogen fuel cells commercially viable, scientists are searching for more affordable catalysts that provide the same efficiency as pure platinum.

“Like a battery, hydrogen fuel cells convert stored chemical energy into electricity. The difference is that you’re using a replenishable fuel so, in principle, that ‘battery’ would last forever,” said Adrian Hunt, a scientist at the National Synchrotron Light Source II (NSLS-II), a U.S. Department of Energy (DOE) Office of Science User Facility at DOE’s Brookhaven National Laboratory. “Finding a cheap and effective catalyst for hydrogen fuel cells is basically the holy grail for making this technology more feasible.”

>Read more on the NSLS-II website

Image: Brookhaven Lab scientists Mingyuan Ge, Iradwikanari Waluyo, and Adrian Hunt are pictured left to right at the IOS beamline, where they studied the growth pathway of an efficient catalyst for hydrogen fuel cells.

Fuel cells from plants

Fuel cells from plants

Using elements in plants to increase fuel cell efficiency while reducing costs

Researchers from the Institut National de la Recherche Scientifique, Québec are looking into reeds, tall wetlands plants, in order to make cheaper catalysts for high-performance fuel cells.

Due to rising global energy demands and the threat caused by environmental pollution, the search for new, clean sources of energy is on.

Unlike a battery, which stores electricity for later use, a fuel cell generates electricity from stored materials, or fuels.

Hydrogen-based fuel is a very clean fuel source that only produces water as a by-product, and could effectively replace fossil fuels. In order to make hydrogen fuel viable for everyday use, high-performance fuel cells are needed to convert the energy from the hydrogen into electricity.

Hydrogen fuel cells use platinum catalysts to drive energy conversion, but the platinum is expensive, accounting for almost half of a fuel cell’s total cost according to Qiliang Wei, a PhD student in Shuhui Sun’s group from the Institut National de la Recherche Scientifique – Énergie, Matériaux et Télécommunications who studies lower-cost alternatives to platinum catalysts.

>Read more on the Canadian Light Source website

Bing-Joe Hwang received National Chair Professorship from Ministry of Education

Bing-Joe Hwang received National Chair Professorship from Ministry of Education

Exceptional award for this NSRRC User

The Ministry of Education recently announced the recipients of the 21st National Chair Professorships and the 61st Academic Awards. Prof. Bing-Joe Hwang, a long-term user of NSRRC, was given the National Chair Professorship in the category of Engineering and Applied Sciences. Prof. Hwang is a Chair Professor in Chemical Engineering at National Taiwan University of Science and Technology. He is also an adjunct scientist of NSRRC. His research interests include electrochemistry, nanomaterials, nanoscience, fuel cells, lithium ion batteries, solar cells, sensors, and interfacial phenomena.

 

>Read More on the NSRRC website

Fuel cell X-Ray study details effects of temperature and moisture on performance

Fuel cell X-Ray study details effects of temperature and moisture on performance

Experiments at Berkeley Lab’s Advanced Light Source help scientists shed light on fuel-cell physics

Like a well-tended greenhouse garden, a specialized type of hydrogen fuel cell – which shows promise as a clean, renewable next-generation power source for vehicles and other uses – requires precise temperature and moisture controls to be at its best. If the internal conditions are too dry or too wet, the fuel cell won’t function well.

But seeing inside a working fuel cell at the tiny scales relevant to a fuel cell’s chemistry and physics is challenging, so scientists used X-ray-based imaging techniques at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and Argonne National Laboratory to study the inner workings of fuel-cell components subjected to a range of temperature and moisture conditions.

The research team, led by Iryna Zenyuk, a former Berkeley Lab postdoctoral researcher now at Tufts University, included scientists from Berkeley Lab’s Energy Storage and Distributed Resources Division and the Advanced Light Source (ALS), an X-ray source known as a synchrotron.

>Read More on the ALS website

Image: This animated 3-D rendering (view larger size), generated by an X-ray-based imaging technique at Berkeley Lab’s Advanced Light Source, shows tiny pockets of water (blue) in a fibrous sample. The X-ray experiments showed how moisture and temperature can affect hydrogen fuel-cell performance.
Credit: Berkeley Lab