Oxidation states study of nickel in solid oxide fuel cell anode using x-ray full-field spectroscopic nano-tomography

Identifying the chemical state and coupling with morphological information in three dimensions are of great interest in energy storage materials, which typically involve reduction-oxidation cycling and structural evolution. Here, we apply x-ray nano-tomography with multiple x-ray energies to study oxidation states of nickel (Ni) and nickel oxide phases in Ni-yttria-stabilized zirconia (YSZ), a typical anode material of solid oxide fuel cells (SOFC). We present a method to quantitatively identify the nickel-based oxides from Ni-YSZ anode composite, and obtain chemical mapping as well as associated microstructures at nanometer scale in three dimensions. NiO particles manually placed on a Ni-YSZ composite anode were used for validation of the method, while no nickel oxides were found to be present within the electrode structure as remnants of the cell fabrication process. The application of the method can be widely applied to energy storage materials including SOFCs, Li-ion batteries, and supercapacitors, as well as other systems for oxidation and reduction study.