Professor Barnett has worked extensively on ceramic thin films and coatings, including hard coatings and transparent conducting oxides. In the area of energy research, Barnett has been studying solid oxide fuel cells for > 25 years. His general areas of interest in fuel cells include novel processing methods including 3D printing and thin electrolyte deposition, electrode reaction mechanisms, intermediate-temperature solid oxide cells, direct utilization of hydrocarbon fuels, 3D imaging of electrode microstructure, and reversible cells for energy storage. He has also worked on studies of Li ion battery electrodes, including 3D tomographic imaging.  Recent research includes studies of reversible solid oxide cells for energy storage applications, and combined electrochemical and microstructural studies of electrode evolution over time, important for predicting the long-term durability of electrochemical devices.