TY - GEN A1 - Gonzalez-Arias, Judith A1 - Torres-Sempere, Guillermo A1 - Gonzalez-Castano, Miriam A1 - Baena-Moreno, Francisco Manuel A1 - Ramirez Reina, Tomas T1 - Hydrochar and synthetic natural gas co-production for a full circular economy implementation via hydrothermal carbonization and methanation: An economic approach T2 - Journal of Environmental Sciences N2 - Herein we study the economic performance of hydrochar and synthetic natural gas co-production from olive tree pruning. The process entails a combination of hydrothermal carbonization and methanation. In a previous work, we evidenced that standalone hydrochar production via HTC results unprofitable. Hence, we propose a step forward on the process design by implementing a methanation, adding value to the gas effluent in an attempt to boost the overall process techno-economic aspects. Three different plant capacities were analyzed (312.5, 625 and 1250 kg/hr). The baseline scenarios showed that, under the current circumstances, our circular economy strategy in unprofitable. An analysis of the revenues shows that hydrochar selling price have a high impact on NPV and subsidies for renewable coal production could help to boost the profitability of the process. On the contrary, the analysis for natural gas prices reveals that prices 8 times higher than the current ones in Spain must be achieved to reach profitability. This seems unlikely even under the presence of a strong subsidy scheme. The costs analysis suggests that a remarkable electricity cost reduction or electricity consumption of the HTC stage could be a potential strategy to reach profitability scenarios. Furthermore, significant reduction of green hydrogen production costs is deemed instrumental to improve the economic performance of the process. These results show the formidable techno-economic challenge that our society faces in the path towards circular economy societies. Y1 - 2023 UR - https://www.sciencedirect.com/science/article/pii/S1001074223001766 U6 - https://doi.org/10.1016/j.jes.2023.04.019 SN - 1878-7320 VL - Vol. 140(2024) SP - 69 EP - 78 ER - TY - GEN A1 - Bobadilla, Luis F. A1 - Azancot, Lola A1 - Luque-Alvarez, Ligia A. A1 - Torres-Sempere, Guillermo A1 - Gonzalez-Castano, Miriam A1 - Pastor-Perez, Laura A1 - Yu, Jie A1 - Ramirez Reina, Tomas A1 - Ivanova, Svetlana A1 - Centeno, Miguel Angel A1 - Odriozola, José Antonio T1 - Development of Power-to-X Catalytic Processes for CO2 Valorisation: From the Molecular Level to the Reactor Architecture T2 - Chemistry N2 - Nowadays, global climate change is likely the most compelling problem mankind is facing. In this scenario, decarbonisation of the chemical industry is one of the global challenges that the scientific community needs to address in the immediate future. Catalysis and catalytic processes are called to play a decisive role in the transition to a more sustainable and low-carbon future. This critical review analyses the unique advantages of structured reactors (isothermicity, a wide range of residence times availability, complex geometries) with the multifunctional design of efficient catalysts to synthesise chemicals using CO2 and renewable H2 in a Power-to-X (PTX) strategy. Fine-chemistry synthetic methods and advanced in situ/operando techniques are essential to elucidate the changes of the catalysts during the studied reaction, thus gathering fundamental information about the active species and reaction mechanisms. Such information becomes crucial to refine the catalyst’s formulation and boost the reaction’s performance. On the other hand, reactors architecture allows flow pattern and temperature control, the management of strong thermal effects and the incorporation of specifically designed materials as catalytically active phases are expected to significantly contribute to the advance in the valorisation of CO2 in the form of high added-value products. From a general perspective, this paper aims to update the state of the art in Carbon Capture and Utilisation (CCU) and PTX concepts with emphasis on processes involving the transformation of CO2 into targeted fuels and platform chemicals, combining innovation from the point of view of both structured reactor design and multifunctional catalysts development. Y1 - 2022 UR - https://www.mdpi.com/2624-8549/4/4/83 U6 - https://doi.org/10.3390/chemistry4040083 SN - 2624-8549 VL - 4 IS - 4 SP - 1250 EP - 1280 ER - TY - GEN A1 - Vinuesa, Guillermo A1 - García, Héctor A1 - Pérez, Eduardo A1 - Wenger, Christian A1 - Íñiguez de la Torre, Ignacio A1 - González, Tomás A1 - Dueñas, Salvador A1 - Castán, Helena T1 - On the asymmetry of Resistive Switching Transitions T2 - Electronics N2 - In this study, the resistive switching phenomena in TiN/Ti/HfO2/Ti metal–insulator–metal stacks is investigated, mainly focusing on the analysis of set and reset transitions. The electrical measurements in a wide temperature range reveal that the switching transitions require less voltage (and thus, less energy) as temperature rises, with the reset process being much more temperature sensitive. The main conduction mechanism in both resistance states is Space-charge-limited Conduction, but the high conductivity state also shows Schottky emission, explaining its temperature dependence. Moreover, the temporal evolution of these transitions reveals clear differences between them, as their current transient response is completely different. While the set is sudden, the reset process development is clearly non-linear, closely resembling a sigmoid function. This asymmetry between switching processes is of extreme importance in the manipulation and control of the multi-level characteristics and has clear implications in the possible applications of resistive switching devices in neuromorphic computing. KW - resistive switching KW - RRAM KW - memristor KW - transient KW - temperature dependence KW - low power consumption Y1 - 2024 U6 - https://doi.org/10.3390/electronics13132639 SN - 2079-9292 VL - 13 IS - 13 PB - MDPI ER - TY - GEN A1 - Vinuesa, Guillermo A1 - Garcia, Hector A1 - Duenas, Salvador A1 - Castan, Helena A1 - Iñiguez de la Torre, Ignacio A1 - Gonzalez, Tomas A1 - Dorai Swamy Reddy, Keerthi A1 - Uhlmann, Max A1 - Wenger, Christian A1 - Perez, Eduardo T1 - Effect of the temperature on the performance and dynamic behavior of HfO2-Based Rram Devices T2 - ECS Meeting Abstracts N2 - Over the past decades, the demand for semiconductor memory devices has been steadily increasing, and is currently experiencing an unprecedented boost due to the development and expansion of artificial intelligence. Among emerging high-density non-volatile memories, resistive random-access memory (RRAM) is one of the best recourses for all kind of applications, such as neuromorphic computing or hardware security [1]. Although many materials have been evaluated for RRAM development, some of them with excellent results, HfO2 is one of the established materials in CMOS domain due to its compatibility with standard materials and processes [2]. The main goal of this work is to study the switching capability and stability of HfO2-based RRAMs, as well as to explore their ability in the field of analogue applications, by analyzing the evolution of the resistance states that allow multilevel control. Indeed, analogue operation is a key point for achieving electronic neural synapses in neuromorphic systems, with synaptic weight information encoded in the different resistance states. This research has been carried out over a wide temperature range, between 40 and 340 K, as we are interested in testing the extent to which performance is maintained or modified, with a view to designing neuromorphic circuits that are also suitable in the low-temperature realm. We aim to prove that these simple, fast, high integration density structures can also be used in circuits designed for specific applications, such as aerospace systems. The RRAM devices studied in this work are TiN/Ti/8 nm-HfO2/TiN metal-insulator-metal (MIM) capacitors. Dielectric layers were atomic layer deposited (ALD). It has been demonstrated that the Ti coat in the top electrode acts as a scavenger that absorbs oxygen atoms from the HfO2 layer, and facilitates the creation of conductive filaments of oxygen vacancies [3]. In fact, the oxygen reservoir capability of Ti is well known, as it is able to attract and release oxygen atoms from or to the HfO2 layer during the RRAM operation [4]. The clustering of vacancies extends through the entire thickness of the oxide and, after an electroformig step, it joins the upper and lower electrodes and the device reaches the low resistance state (LRS). By applying adequate electrical signals, the filaments can be partially dissolved, which brings the device into the high-resistance state (HRS), with lower current values. The set process brings the device to the LRS state, while the reset one brings it to the HRS. The dependence of electrical conductivity on external applied electrical excitation allows triggering the device between the both states in a non-volatile manner [5]. The experimental equipment used consisted of a Keithley 4200-SCS semiconductor parameter analyzer and a Lake Shore cryogenic probe station. Fig.1 shows current-voltage cycles measured at different temperatures; the averages values at each temperature, both in logarithmic and linear scale, are also shown. The functional window increases as temperature decreases. The evolutions of set and reset voltage values with temperature are depicted in Fig.2, whereas the current values (measured at 0.1 V) corresponding to the LRS and HRS can be seen in Fig.3. LRS resistance decreases as temperature increases, in agreement with semiconductor behaviour, probably due to a hopping conduction mechanism. Both set and reset voltages decrease as temperature increases; the reset process is smoother at high temperatures. The reduction in reset voltage variability as temperature increases is very notable. Finally, Fig. 4 shows a picture of the transient behaviour; in the right panel of the same figure, the amplitudes of the current transients in the reset state have been included in the external loop. To sum up, the resistive switching phenomena is studied in a wide temperature range. The LRS shows semiconducting behavior with temperature, most likely related to a hopping conduction mechanism. Switching voltages decrease as temperature increases, with a notable reduction in reset voltage variability. An excellent control of intermediate resistance state is shown through current transients at several voltages in the reset process. REFERENCES [1] M. Asif et al., Materials Today Electronics 1, 100004 (2022). [2] S. Slesazeck et al., Nanotechnology 30, 352003 (2019). [3] Z. Fang et al., IEEE Electron Device Letters 35, 9, 912-914 (2014). [4] H. Y. Lee et al., IEEE Electron Device Letters 31, 1, 44-46 (2010). [5] D. J. Wouters et al., Proceedings of the IEEE 103, 8, 1274-1288 (2015). Figure 1 KW - RRAM Y1 - 2024 U6 - https://doi.org/10.1149/MA2024-01211297mtgabs SN - 2151-2043 VL - MA2024-01 IS - 21 SP - 1297 EP - 1297 PB - The Electrochemical Society ER - TY - GEN A1 - De Tomás Marín, Sergio A1 - Rodríguez-Calcerrada, Jesús A1 - Arenas-Castro, Salvador A1 - Prieto, Iván A1 - González, Guillermo A1 - Gil, Luis A1 - Garcia de la Riva, Enrique T1 - Fagus sylvatica and Quercus pyrenaica: Two neighbors with few things in common T2 - Forest Ecosystems KW - Environmental niche KW - European beech KW - Forest dynamics KW - Functional niche KW - Hypervolume KW - Pyrenean oak KW - Species coexistence KW - Sub-Mediterranean community Y1 - 2023 U6 - https://doi.org/10.1016/j.fecs.2023.100097 SN - 2197-5620 VL - 10 ER -