Abstract: We report the development of a facile recycling process for catalyst coated membranes (CCMs) used in polymer electrolyte membrane (PEM) water electrolyzers. After performance evaluation in an assembled electrolysis cell, ultrasonication is used to provide high-yield recovery of not only the noble-metal catalyst materials, but also of the fluoropolymer membrane itself, without the release of hazardous gases. Transmission electron microscopy (TEM) and electrochemical characterization are used to confirm the retention of catalyst particle size, and of the performance of the recycled CCMs. Furthermore, our projections indicate that, if this approach is widely employed, existing resources of noble metals will prove sufficient for the gigawatt-scale implementation of PEM water electrolyzers. This has profound implications for the achievement of current targets for reducing the consumption of precious metals for applications in electrolyzers, fuel cells and other energy storage devices.

Abstract: Steam reforming, CO2 reforming, and simultaneous steam and CO2 reforming of methane to CO and H2 over NiO-CaO catalyst (without any prereduction treatment) at different temperatures (700-850 ° C) and space velocities (5000-70\,000 cm3$\cdot$g-1$\cdot$h-1) are investigated. The catalyst is characterized by XRD, XPS, and temperature-programmed reduction (TPR). The catalyst showed high activity/selectivity in both the steam and CO2 reforming reactions and the simultaneous steam and CO2 reforming. In the CO2 reforming, the coke deposition on the catalyst is found to be very fast. However, when the CO2 reforming is carried out simultaneously with the steam reforming, the coke deposition on the catalyst is drastically reduced. By the simultaneous CO2 and steam reforming (at $\geq$800 ° C and space velocity of about 20\,000-30\,000 cm3$\cdot$g-1$\cdot$h-1), methane can be converted almost completely to syngas with 100% selectivity for both CO and H2. The H2/CO ratio in products can be varied between 1.5 and 2.5 quite conveniently by manipulating the relative concentration of steam and CO2 in the feed.

Abstract: To decrease the use of fossil fuels and face the energetic demand, the integration of renewable energy is a necessary step. Part of this renewable energy can be supplied by the production of electricity from photovoltaic panels and windfarms. The massive use of these intermittent energies will lead to overproduction periods, and there is consequently a need to convert this surplus of electricity into a storable form of energy. Power-to-gas (PtG) technology consists in using electricity to convert water into hydrogen by electrolysis, and then to synthetize methane from carbon dioxide and hydrogen. Techno-economic and Life Cycle Assessment of methane production via the combination of anaerobic digestion and PtG technology have been applied to sewage sludge valorization. Process studies and equipment design have been addressed considering already available technologies. Sensitivity analyses have been done on biogas upgrading technologies, electricity prices, annual operation time and composition of the electricity mix with also a comparison between PtG and direct injection. It appears that the more the electricity is expensive, the longer the operation time of the methanation process must be to be competitive with injection of methane from biogas. Reduction of electricity consumption of the electrolysis step decreases production costs. Even if the current context does not feature adapted conditions to ensure an economically viable chain, the evolution of the energetic context in the next few years as well as the expected technological improvements will contribute to overall cost reduction. From an environmental point of view, continuous PtG generates more greenhouse gases than direct injection, but intermittent operation with use of renewable electricity can significantly reduce GHG emissions. From an endpoint impacts perspective, impact from continuous PtG are higher than biogas upgrading, but much lower than fossil energy. Future development of low electricity consumption of the electrolysis process, and integration of renewable credits from CO2 valorization can increase the competitiveness of this technology.