Advanced materials for energy harvesting, storage, sensing and environmental engineering Mohamed El Jouad, Rachid Bennacer, Mohammed El Ganaoui and Jean-Michel Nunzi Eur. Phys. J. Appl. Phys., 88 2 (2019) 20903 Published online: 05 February 2020 DOI: 10.1051/epjap/2020190360