Anaerobic digestion of sewage sludge produces large amounts of CO₂ which contribute to global CO₂ emissions. Capture and conversion of CO₂ into valuable products is a novel way to reduce CO₂ emissions and valorize it. Membrane contactors can be used for CO₂ capture in liquid media, while bioelectrochemical systems (BES) can valorize dissolved CO₂ converting it to CH₄, through electromethanogenesis (EMG). At the same time, EMG process, which requires electricity to drive the conversion, can be utilized to store electrical energy (eventually coming from renewables surplus) as methane. The study aims integrating the two technologies at a laboratory scale, using for the first time real wastewater as CO₂ capture medium. Five replicate EMG-BES cells were built and operated individually at 0.7 V. They were fed with both synthetic and real wastewater, saturated with CO₂ by membrane contactors. In a subsequent experimental step, four EMG-BES cells were electrical stacked in series while one was kept as reference. CH₄ production reached 4.6 L CH₄ m⁻² d⁻¹, in line with available literature data, at a specific energy consumption of 16–18 kWh m⁻³ CH₄ (65% energy efficiency). Organic matter was removed from wastewater at approximately 80% efficiency. CO₂ conversion efficiency was limited (0.3–3.7%), depending on the amount of CO₂ injected in wastewater. Even though achieved performances are not yet competitive with other mature methanation technologies, key knowledge was gained on the integrated operation of membrane contactors and EMG-BES cells, setting the base for upscaling and future implementation of the technology.

Large Stokes shift downshifting organolanthanide complex, Eu(tta)₃phen, is examined for inclusion in polymeric layers to replace the UV blocking layer in dye sensitized solar cell (DSSC) technology. The UV blocking layer increases stability but power conversion efficiency decreases as incident UV photons are not converted into photocurrent. Eu(tta)₃phen doped polymeric film are prepared and attached to DSSC devices following optimized thickness and concentration from a ray‐trace numerical model for the specific DSSC. External quantum efficiency is significantly increased in the UV spectral region compared to DSSCs utilizing a passive, non‐luminescent, UV‐BL. High Eu(tta)₃phen film transparency in the visible range minimizes DSSC EQE losses at visible wavelengths. Short‐circuit current (I_sc) enhancement due to downshifting is demonstrated (∼1%) in small‐scale DSSC prototypes, where the specific geometry limits the photon collection efficiency and overall enhancement. Model predictions indicate that 2%–3% Isc enhancement is realizable in flexible single DSSC compared to, non‐luminescent, UV‐BL. Added to this, in outdoor conditions taking into account diffuse light, the increment in I_sc can increase 50% more. Although photostability of the blended LSS‐DS polymer films is not sufficient to be useful for medium‐long term outdoor PV applications, the results demonstrate that significant efficiency enhancement can be realized.

This paper deals with the design, operation, modeling, and grid integration of bioelectrochemical systems (BES) for power-to-gas application, through an electromethanogenesis process. The paper objective is to show that BES-based power-to-gas energy storage is feasible on a large scale, showing a first approximation that goes from the BES design and operation to the electrical grid integration. It is the first study attempting to cover all aspects of a BES-based power-to-gas technology, on authors’ knowledge. Designed BES reactors were based on a modular architecture, suitable for a future scaling-up. They were operated in steady state for eight months, and continuously monitored in terms of power consumption, water treatment, and biomethane production, in order to obtain data for the following modeling activity. A black box linear model of the BES was computed by using least-square methods, and validated through comparison with collected experimental data. Afterwards, a BES stack was simulated through several series and parallel connections of reactors, in order to obtain higher power consumption and test the grid integration of a real application system. The renewable energy surplus and energy price variability were evaluated for the grid integration of the BES stack. The BES stack was then simulated as energy storage system during low energy price periods, and tested experimentally with a real time system.

High-performance and cost-efficient electrocatalysts and electrodes are needed to improve the hydrogen evolution reaction (HER) for the hydrogen (H₂) generation in electrolysers, including microbial electrolysis cells (MECs). In this study, free-standing carbon nanofiber (CNF) films with supported cobalt phosphide nanoparticles have been prepared by means of an up-scalable electrospinning process followed by a thermal treatment under controlled conditions. The produced cobalt phosphide-supported CNF films show to be nanoporous (pore volume up to 0.33 cm³ g⁻¹) with a high surface area (up to 502 m² g⁻¹) and with a suitable catalyst mass loading (up to 0.49 mg cm⁻²). Values of overpotential less than 140 mV at 10 mA cm⁻² have been reached for the HER in alkaline media (1 M KOH), which demonstrates a high activity. The high electrical conductivity together with the mechanical stability of the free-standing CNF films allowed their direct use as cathodes in a MEC reactor, resulting in an exceptionally low voltage operation (0.75 V) with a current density demand of 5.4 A m⁻². This enabled the production of H₂ with an energy consumption below 30 kWh kg⁻¹ H₂, which is highly efficient.