1. Electrochemical performance of ErCl3 pseudocapacitor. (a) The charge/
discharge curves (time versus potential) measured at various current densities and
a potential range of 0.55 V. (b) Specific capacitance of inorganic ErCl3 salt electrode
versus discharge current density at potential window of 0.55 V based on the weight
of ErCl36H2O salt and Er3+ ion. All data are taken in a 2 M KOH electrolyte at room
temperature