Effect of Platinum Content on Properties of CNT-Supported Pt-Mo Catalyst for Ethanol Electrooxidation Reaction

The CNT-supported nanodispersed Pt-Mo catalysts for the ethanol electrooxidation reaction in the alkaline solution are synthesized and their characteristics are studied. Based on the XPS studies in a wide range of platinum content (10-40 wt %), it is found that in the composition of the catalysts, platinum is predominantly in the metallic state, and molybdenum is in the hexavalent form, probably in the form of MoO₃ oxide. According to the XRD and electrochemical studies, the Pt/CNT and PtMo/CNT catalysts with equal platinum contents (~20 wt %) are characterized by similar platinum crystallite sizes (5-10 nm) and electrochemically accessible surface areas (23-26 m²/g_Pt). This indicates that platinum is not shielded by the molybdenum compounds. When the platinum content increases above 20 wt %, the Pt:Mo atomic ratio increases (the nominal ratio is 1:1), which may be due to the decoration of molybdenum oxide with platinum nanoparticles. A study of the kinetics of the ethanol electrooxidation reaction showed that the activity of the PtMo/CNT system is higher than that of the Pt/CNT catalyst. However, the efficiency of platinum use decreases as its content in the PtMo/CNT system increases from 10 to 40 wt %. On the other hand, the systems containing 20-40 wt % Pt exhibit the highest activity per unit catalyst weight, making them very promising for use as a component of the anode active layer of a fuel cell. The tests of the alkaline ethanol fuel cell based on the synthesized catalysts show the maximum power density of 29 mW/cm², which corresponds to the level of the best literature parameters under similar experimental conditions.