CsH$_{\mathrm{2}}$PO$_{\mathrm{4\thinspace }}$superprotonic phase stabilization attempts*

CsH$_{\mathrm{2}}$PO$_{\mathrm{4}}$ (CDP) is one of the most promising electrolytes for proton exchange membrane fuel cells in the intermediate temperature range (200 - 400 ${^\circ}$C). One of the biggest challenges is the stabilization of the ``superprotonic'' phase present in CDP when it is heated above 231${^\circ}$C. We performed XRD and Impedance Spectroscopy (IS) on pure CDP and composites under ambient and humidified atmospheres. XRD confirmed the presence of the cubic phase of CDP with space group Pm-3m during a short interval of temperature and time. Although previously reported in the literature to appear only in the presence of a humidified atmosphere, IS showed the presence of the highly conductive phase also during a short time interval. Silica additive and a humidified atmosphere increase the stability of the superprotonic phase.