The presence of an additional shoulder in the O 1s peak of Ni 4 V 3 O 10 also reveals moisture contamination on the surface. This effect has been noted in samples of V 2 O 5 , vanadium-yttrium hydrates, and NiO. This oxide/hydroxide layer likely protects vanadium near the surface of Ni 4 V 3 O 10 from oxidizing to V 5+ in air. This data, though, cannot reveal the presence of multiple oxidation states within the bulk of the material.