• Energy Research

The development of new membranes cheaper than Nafion®, with similar conductivity and lower hydrogen/methanol cross-over, is crucial for widespread commercial applications of Polymer Electrolyte Membrane Water Electrolysers (PEMWEs) and Direct Methanol Fuel Cells (DMFCs) [1, 2]. This study reports on the synthesis and development of PEMs based on sulfonated polysulfone (sPSf) for application both in WEs and DMFCs at different operating temperatures. The sPSf was synthesized by using trimethyl silyl chlorosulfonate as sulfonating agent in a homogeneous phase of chloroform [3]. In order to try to reduce methanol crossover in DMFCs, functionalized silica was prepared (by reacting silica with neat chlorosulfonic acid at room temperature) and added as a filler in the sPSf membrane. The prepared membranes were physico-chemically characterized and used as electrolytes in PEMWEs and DMFCs [4, 5]. Besides, the transport properties of water and methanol through the electrolyte membranes as a function of methanol concentration (e.g. 1M - 5M CH3OH) and temperature (from room temperature up to 80°C) were analyzed by using Pulse Field Gradient (PFG) NMR technique. References [1] A. S. Aricò, S. Siracusano, N. Briguglio, V. Baglio, A. Di Blasi, V. Antonucci, J. Appl. Electrochem. 43 (2013) 107-118. [2] F. Lufrano, V. Baglio, P. Staiti, V. Antonucci, A.S. Aricò, J. Power Sources 243 (2013) 519-534. [3] F. Lufrano, V. Baglio, P. Staiti, A. Stassi, A.S. Aricò, V. Antonucci, J. Power Sources 195 (2010) 7727-7733. [4] S. Siracusano, V.Baglio, F.Lufrano, P.Staiti, A.S.Aricò, Journal of Membrane Science 448 (2013) 209-214. [5] F. Lufrano, V. Baglio, O. Di Blasi, P. Staiti, V. Antonucci, A. S. Aricò, Phys. Chem. Chem. Phys. 14 (2012) 2718-2726.

An innovative tandem photoelectrochemical cell with a scaled-up active area from 0.25 to 25 cm2 based on low-cost and non-critical raw materials was employed to produce green hydrogen by water splitting. It uses a photoanode/membrane/photocathode tandem cell configuration in which a hematite-based photoanode is layered on a fluorine-doped tin oxide glass for the oxygen evolution reaction, CuO is deposited on a hydrophobic gas diffusion layer as the photocathode for the hydrogen evolution reaction and an anion exchange membrane is used as the electrolyte and gas separator. The solid membrane's low hydrogen and oxygen crossover guarantees the operational stability of the tandem photoelectrochemical cell and the efficient separation of water-splitting products. Significant efforts have been focused on scaling up the cell. It has allowed obtaining, for the first time, a 25 cm2 unit cell prototype. Appropriate design approaches have been considered to optimise water/gas management, current collection, gas-tightness and clamping. The adopted architecture allowed for the reduction of the bias-potential from −1.23 V, generally employed to investigate PEC cells, up to −0.6/-0.4 V 20 h-durability tests demonstrated good resistance to corrosion, showing a constant photocurrent. Efficiency at −0.6 V was about 0.2%. Selective hydrogen production was demonstrated by mass spectrometric analysis.

AbstractIn the last 20 years, direct alcohol fuel cells (DAFCs) have been the subject of tremendous research efforts for the potential application as on-demand power sources. Two leading technologies respectively based on proton exchange membranes (PEMs) and anion exchange membranes (AEMs) have emerged: the first one operating in an acidic environment and conducting protons; the second one operating in alkaline electrolytes and conducting hydroxyl ions. In this review, we present an analysis of the state-of-the-art acidic and alkaline DAFCs fed with methanol and ethanol with the purpose to support a comparative analysis of acidic and alkaline systems, which is missing in the current literature. A special focus is placed on the effect of the reaction stoichiometry in acidic and alkaline systems. Particularly, we point out that, in alkaline systems, OH− participates stoichiometrically to reactions, and that alcohol oxidation products are anions. This aspect must be considered when designing the fuel and when making an energy evaluation from a whole system perspective. Graphical Abstract

A co-planar micro Direct Methanol Fuel Cell (p.DMFC) configuration was designed, developed and tested. The system geometry consisted of anodic and cathodic micro-channels arranged in the same plane. Firstly, micro-channels for a uniform distribution of oxygen and methanol were designed and realized on a polymeric substrate of polycarbonate. Then, the deposition of the catalytic elements inside the micro-channels by a spray-coating technique was carried out. Micro-channels were then covered by a catalyzed membrane containing separate anode and cathode layers. Different cell configurations were built, tested and evaluated. It was observed that the open circuit voltage varied significantly as a function of the membrane humidification degree and distance between anode and cathode channels in this planar design. In the presence of a large distance between the anode and cathode channel, the OCV reached 0.97 V. This high OCV reflected the absence of methanol cross-over due to the specific planar configuration. Regrettably, the overall cell impedance (ohmic and polarization resistance) limited the performance. A maximum power density of 1.3 mW cm(-2) (active area) was achieved at room temperature with the smallest distance between anode and cathode (0.25 mm).

Three cathode catalysts (60% Pt/C, 30% Pt/C and 60% Pt–Fe/C), with a particle size of about 2–3 nm, were prepared to investigate the effect of ethanol cross-over on cathode surfaces. All samples were studied in terms of structure and morphology by using X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. Their electrocatalytic behavior in terms of oxygen reduction reaction (ORR) was investigated and compared using a rotating disk electrode (RDE). The tolerance of cathode catalysts in the presence of ethanol was evaluated. The Pt–Fe/C catalyst showed both higher ORR activity and tolerance to ethanol cross-over than Pt/C catalysts. Moreover, the more promising catalysts were tested in 5 cm2 DEFC single cells at 60 and 80 °C. An improvement in single cell performance was observed in the presence of the Pt–Fe catalyst, due to an enhancement in the oxygen reduction kinetics. The maximum power density was 53 mW cm−2 at 2 bar rel. cathode pressure and 80 °C.

Abstract A new generation of highly efficient and non-polluting energy conversion and storage systems is vital to meeting the challenges of global warming and the finite reality of fossil fuels. In this work, nanosized Pt/IrO2 electrocatalysts are synthesized and investigated for the oxygen evolution and reduction reactions in unitized regenerative fuel cells (URFCs). The catalysts are prepared by decorating Pt nanoparticles (2–10 nm) onto the surface of a nanophase IrO2 (7 nm) support using an ultrasonic polyol method. The synthesis procedure allows deposition of metallic Pt nanoparticles on Ir-oxide without causing any occurrence of metallic Ir. The latter is significantly less active for oxygen evolution than the corresponding oxide. This process represents an important progress with respect to the state of the art in this field being the oxygen electrocatalyst generally obtained by mechanical mixing of Pt and IrO2. The nanosized Pt/IrO2 (50:50 wt.%) is sprayed onto a Nafion 115 membrane and used as dual function oxygen electrode, whereas 30 wt.% Pt/C is used as dual function hydrogen electrode in the URFC. Electrochemical activity of the membrane-electrode assembly (MEA) is investigated in a single cell at room temperature and atmospheric pressure both under electrolysis and fuel cell mode to assess the perspectives of the URFC to operate as energy storage device in conjunction with renewable power sources.