Erbium compound materials, such as ErOOH and Er2O3, are recognized
as one of the most important rare earth oxides for sensing
applications in the lasers and optical amplifiers, due to intra-Er3+ 4f
shell transition from its first excited state (4I3/2) to the ground state
(4I5/2) [20]. Recently, flaky rare earth oxide including Er2O3 was
used as additives on nickel electrodes and their effects on high
temperature performance of nickel electrodes were investigated
[21]. The result proved that flaky rare earth oxides increased the
oxygen evolution potential and improved the reversibility of nickel
electrodes. To the best of our knowledge, Er-based super capacitors
have not been reported. In one case, Er(OH)3 was used to increase
structural and electro chemical stability of Co–Al layered double
hydroxide pseudo capacitor [22]. Less soluble of Er(OH)3 can adhere
to the Co–Al layered double hydroxide more strongly, stop the
directly contact of OH, and thus inhibit leaking process of Al3+.