On the Effect of Platinum Loading on Electrochemical Parameters of Gas Diffusion Electrodes Sputtered by Magnetron

In this paper, we study the effect of platinum loading on the structure, density, and uniformity of deposition of a platinum film sputtered by a magnetron, as well as on the electrochemical characteristics of the deposited electrodes, such as the electrochemically active surface area of platinum (EASA), the durability of the electrodes, and the electrochemical performance of membrane-electrode assemblies of a fuel cell generally. An increase in the mean diameter of individual platinum particles from 1.5 to 3.8 nm and particle agglomerates from 5 to 12 nm, respectively, is shown to be observed as the platinum loading in the samples increases from 0.15 to 1.65 mg/cm2. A decrease in the EASA of catalysts occurs due to an increase in the thickness of the sputtered film and partial overlap of the active sites of the electrocatalyst. In this case, the platinum film is a nanostructured catalytic layer with a high degree of uniformity of the deposited metal. The catalytic layers obtained by sputtering platinum using a magnetron in a pulsed mode are characterized by high values ​​of the active surface up to 112 m2/g and improved durability due to the strong interaction of active sites and carbon particles of the substrate, which is confirmed by the results of X-ray diffraction analysis. EASA losses of platinum in the process of stress testing for deposited electrodes were about 20%, which is twice lower than that for catalytic layers based on platinum powder electrocatalysts. The current–voltage characteristics of a fuel cell with deposited electrodes as a cathode increase with increasing the platinum film thickness. The maximal characteristics were obtained for electrodes with a platinum film thickness of about 100 and 200 nm; values ​​of 0.43 and 0.52 A/cm2 were obtained at 0.5 V.