• Energy Research

Here, in-house CoNC and FeNC have been prepared by, first, chelating the metals (Co or Fe) with ethylene diamine tetra acetic acid, known as EDTA (nitrogen precursor). UV-Visible (UV-Vis) spectrometry has been used to ensure the chelated metal formation. In the next step, the chelated metals have been deposited on a high surface area oxidized carbon support to increase the electrical conductivity. The latter composite material has been thermally treated at 800 °C (CoNC8 and FeNC8) or 1000 °C (CoNC10 and FeNC10) in nitrogen atmosphere in order to create the catalytic sites that will be able to perform the oxygen reduction reaction (ORR) in the acid medium. Electrochemical tests have been carried out to investigate the activity and durability of the electro-catalysts for the ORR. Methanol tolerance properties have been also evaluated for a possible application in direct methanol fuel cells. It appears that FeNC8 is the most active electrocatalyst in the presence of methanol in the base electrolyte, thus showing promising characteristics for direct methanol fuel cells. Instead, stability tests of these metal nitrogen catalysts indicate the best resistance to corrosion for the catalysts treated at 1000 °C.

The co-electrolysis of CO2 and H2O at intermediate temperature is a viable approach for the power-to-gas conversion that deserves for further investigation, considering the need for green energy storage. The commercial solid oxide electrolyser is a promising device, but it is still facing to solve issues concerning the high operating temperatures and the improvement of gas value. In this paper we reported the recent findings of a simple approach that we have amply suggested for solid oxide cells consisting in the addition of a functional layer coated to the fuel electrode of commercial electrochemical cells. This approach simplifies the transition to the next generation of cells manufactured with the most promising materials currently developed and improves the gas value in the outlet stream of cell. Here, the material in use as a coating layer consisted of a Ni-modified La0.6Sr0.4Fe0.8Co0.2O3 which was developed and demonstrated as promising fuel electrode for solid oxide fuel cells. The results discussed in this paper proved the positive role of Ni-modified perovskite as a coating layer for the cathode, since an improvement of about twice was obtained about the quality of gas produced.

Abstract This study deals with an investigation of the direct oxidation of organic fuels with different molecular weights in Solid Oxide Fuel Cells (SOFCs). It aims to demonstrate that the final products of the oxidation process are essentially CO 2 and water with a very low amount of secondary products. An anodic catalyst formulation characterized by mixed electronic–ionic conductivity (MIEC) in combination with ceria electrolyte was used for this purpose. The anodic catalyst consisted in a composite Ni-modified perovskite mixed with Ce 0.9 Gd 0.1 O 2 . It provided reasonable fuel flexibility in SOFCs. To get insight into the reaction mechanism, the same anode formulation was investigated in an ex-situ autothermal reforming test. The performances achieved with the direct utilization of both gaseous and liquid fuels appear promising for SOFC applications in remote and micro-distributed energy generation as well as for portable power sources. The anode layer demonstrated stable performance with very low amount of carbon deposition during more than 130 h testing under a direct utilization mode of dry organic fuels.

For the first time methanol tolerant Platinum Group Metal-free (PGM-free) Oxygen Reduction Reaction (ORR) electrocatalyst commercially available on market is integrated into the cathodic layer of highly performed Direct Methanol Fuel Cell (DMFC). The intrinsic ORR activity of Fe-N-C electrocatalyst is studied by Rotating Disk Electrode (RDE) technique with and with no methanol added, confirming material inactivity towards Methanol Oxidation Reaction (MOR). The electrocatalyst is tested in DMFC conditions where such important parameters as catalyst:ionomer ratio, concentration of methanol and operational temperature are varied and optimized for highest performance. The obtained activity and methanol tolerance in RDE measurements of commercial Fe-N-C catalyst is found to be comparable with previously reported state-of-the-art PGM-free cathodic materials. Furthermore, this material, used at the cathode compartment of a DMFC, allows reaching the highest power density recorded for PGM-free catalysts in a DMFC until now under similar conditions.

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.

Solid oxide fuel cell (SOFC) is a mature opportunity for producing power energy in remote areas like islands, where access to the electrical grid is not favoured, and gas distribution is the only viable approach. In this context, generally, biogas represents the most convenient fuel resources in these areas. However, the direct use of biogas in SOFCs is still an issue to be solved due to its negative effect on the conventional Ni-YSZ anode. In this study, to overcome this issue, we suggested using a protective layer coated on the anode of a commercial SOFC. A nickel manganite showing mixed ionic and electronic conductivity tailored specifically for this approach was investigated. The preliminary characterisations showed that the formation of a Ruddlesden-Popper (RP) n ¼ 1 structure supporting fine encapsulated particles based on Ni was formed around 800 C in consequence of the reducing environment. The electrochemical experiments carried out for 270 h demonstrated for the coated cell significant stability in the presence of dry biogas, albeit an ageing effect was noticed in the electrical percolation of both cell electrodes. The post mortem analyses revealed an attractive redox property for the nickel manganite, which partially returned to the RP n ¼ 2 phase. Moreover, the absence of carbon deposits on the anode suggests possible applications for this approach.

Water electrolysis supplied by renewable energy is the foremost technology for producing "green" hydrogen for fuel cell vehicles. In addition, the ability to rapidly follow an intermittent load makes electrolysis an ideal solution for grid-balancing caused by differences in supply and demand for energy generation and consumption. Membrane-electrode assemblies (MEAs) designed for polymer electrolyte membrane (PEM) water electrolysis, based on a novel short-side chain (SSC) perfluorosulfonic acid (PFSA) membrane, Aquivion®, with various cathode and anode noble metal loadings, were investigated in terms of both performance and durability. Utilizing a nanosized Ir0.7Ru0.3Ox solid solution anode catalyst and a supported Pt/C cathode catalyst, in combination with the Aquivion® membrane, gave excellent electrolysis performances exceeding 3.2 A·cm-2 at 1.8 V terminal cell voltage (~80 % efficiency) at 90 °C in the presence of a total catalyst loading of 1.6 mg?cm-2. A very small loss of efficiency, corresponding to 30 mV voltage increase, was recorded at 3 A?cm-2 using a total noble metal catalyst loading of less than 0.5 mg·cm-2 (compared to the industry standard of 2 mg·cm-2). Steady-state durability tests, carried out for 1000 h at 1 A?cm-2, showed excellent stability for the MEA with total noble metal catalyst loading of 1.6 mg·cm-2 (cell voltage increase ~5 ?V/h). Moderate degradation rate (cell voltage increase ~15 ?V/h) was recorded for the low loading 0.5 mg·cm-2, MEA. Similar stability characteristics were observed in durability tests at 3 A·cm-2. These high performance and stability characteristics were attributed to the enhanced proton conductivity and good stability of the novel membrane, the optimized structural properties of the Ir and Ru oxide solid solution and the enrichment of Ir species on the surface for the anodic catalyst.