Upcycling natural limestone waste for thermochemical energy storage by utilising tailored CaZrO 3 nanoadditives Rehan Anwar a , Jan Navrátil, b,c Rajani K. Vijayaraghavan, d Patrick J. McNally, d Michal Otyepka, b,e Piotr Błoński, b M. Veronica Sofianos a* a School of Chemical and Bioprocess Engineering, University College Dublin, Belfield, Dublin 4, Ireland, b Regional Centre of Advanced Technologies and Materials, Czech Advanced Technology and Research Institute (CATRIN), Palacký University, Šlechtitelů 27, 783 71, Olomouc, Czech Republic, c Department of Physical Chemistry, Faculty of Science, Palacký University, 17. listopadu 1192/12, 779 00 Olomouc, Czech Republic, d School of Electronic Engineering, Dublin City University, Glasnevin, Dublin 9, Ireland, e IT4Innovations, Technical University of Ostrava, 708 00 Ostrava-Poruba, Czech Republic The development of long-term renewable energy storage systems is crucial for decarbonising the energy sector and enabling the transition to a sustainable energy future. Thermochemical energy storage (TCES) systems are well suited for the long-term renewable energy storage as the materials used in these systems have high energy densities, and long storage duration. 1 Among the plethora of TCES materials, calcium carbonate (Limestone) is of particular interest since it exhibits a high enthalpy of reaction, and it is Earth-abundant. 2 The main problem with Limestone inhibiting its commercial application for long-term renewable energy storage is its deteriorating cycling performance after several energy charge/discharge cycles. In this study, two CaZrO 3 nanoadditives with two different Ca:Zr ratios and tailored oxygen vacancies were synthesised by a precipitation method, and mixed with Limestone waste at three weight concentrations (5,10 and 20 wt%). Their phase, chemical state and morphology was determined by XRD, XPS and TEM, respectively. The cycling performance of the mixture samples was determined through thermogravimetric analysis. The best performing sample was the one mixed with 20% CaZrO 3 nanoadditives, which contained a large number of oxygen vacancies and thus enhanced ionic conductivity, as confirmed by density functional theory (DFT) calculations. This sample exhibited the best effective conversion and the highest energy density values of 0.7 and 2640 kJ/kg, respectively, after 40 cycles. References 1. U. Pelay, L. Luo, Y. Fan, D. Stitou and M. Rood, Renewable and Sustainable Energy Reviews , 2017, 79 , 82-100. 2. Y. Yang, Y. Li, X. Yan, J. Zhao and C. Zhang, Energies , 2021, 14 , 6847.
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