Electrochemical Deposition of Nanocatalysts on an Oxide Scaffold Enhances the Activity of Oxygen Reduction

Abstract

Solid oxide fuel cells (SOFCs) are devices that directly convert the chemical energy of hydrogen and oxygen into electrical energy, and are attracting attention for their high efficiency and eco-friendliness. Since the recent research trend is to lower the operating temperature of the device, there is a considerable demand for a way to effectively introduce a catalyst to overcome the poor electrochemical activity of the most commercially available lanthanum strontium manganite–yttria-stabilized zirconia (LSM-YSZ) composite electrode. Praseodymium oxide (PrO x ) is an excellent catalyst for the ORR and has also been applied to LSM-YSZ electrodes via infiltration, the most widely used catalyst fabrication method. However, this previously well-established method still experiences time-consuming and energy-intensive limitations; therefore, other catalyst fabrication approaches are required. Cathodic electrochemical deposition (CELD) is chosen as a central strategy to decorate the PrO x catalyst which strongly empowers the exclusive ORR activity of the LSM-YSZ electrode. CELD is an excellent catalyst fabrication method that combines electroplating and chemical precipitation, and is simple, fast, cost-effective, and capable of deposition at room temperature and ambient pressure. Herein, we present an electrochemical deposition method that fabricating a PrO x overlayer significantly improves the catalytic activity of composite electrodes with only a short process of less than 4 min, even in an ambient environment. Moreover, it does not require additional processes such as heat treatment. The PrO x -coated electrode exhibits a decrease in initial polarization resistance compared to the bare, and maintained an oxygen reduction reaction characteristic by more than 10 times even after about 400 hours of operation at 650 °C. Transmission line model analysis with impedance spectra describes how PrO x improves the reactivity of the oxygen reduction reaction of composite electrodes. Finally, we demonstrate that a two-element material, (Pr, Ce)O x , was electrochemically deposited. Electrochemical deposition considerably improves the catalytic properties of the cathode via a concise and straightforward process.