The effect of nickel oxide in the direct growth of MnOx on Ni foam by chemical vapor deposition

Manganese oxide has emerged as a promising material for use as a charge storage electrode material. In this work, we demonstrate the low-pressure chemical vapour deposition (CVD) growth of manganese oxide conformal coatings on Ni-foams utilising an MnCl2 solid source precursor, utilising an oxide formed on the surface of the Ni-foam as an oxygen reservoir for the synthesis of a predominantly MnO x layer. The resulting MnO x layer is highly dependent on sample pre-treatment, owing to modifications in the Ni oxide layer. The phase structure, electronic states, morphology, and electrochemical analysis were determined by x-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning-electron microscopy (FE-SEM), and capacitance–voltage (CV) measurements. The importance of the oxide layer is demonstrated by modifying the thickness of the NiO layer over the Ni foam, with clear changes in the resultant structure, morphology, and areal capacitance, with the highest performance MnO x coating found to be obtained without any oxide removal from the Ni foam substrate.