“…The corresponding to V 5+ 2p3/2 and V 5+ 2p 1/2 [45][46]. At the same time, the V 4+ peaks are also found at 515.7 eV (V 4+ 2p3/2) and 523.8 eV (V 4+ 2p1/2) [47], indicating the existence of low valence state vanadium. The relative atomic ratio of V 5+ and V 4+ is 11: 1 calculated based on the peak areas, which suggests the existence of oxygen vacancies in the lattice of V 2 O 5 to compensate the low valence ions of V 4+ [48][49].…”