Effect of Composition of La and Sc on Synergetic Improvement of Activity and Stability in the Ternary Pt alloy for Hydrogen Evolution Reaction

Abstract

As the rapid development of fuel cell and hydrogen industries are observed recently, a necessity of hydrogen infrastructure for production and transportation has been attracted great attention. Because steam reforming and partial oxidation of natural gas are the main methods to produce hydrogen at present, water electrolysis should be investigated to generate the ‘green’ hydrogen for the emerging a hydrogen economy. For a large-scale application, economic, efficient and stable catalysts towards hydrogen evolution reaction (HER) are essential. Although Pt is well known state-of-the-art electrocatalyst for HER, scarcity and expensive price of Pt are main hindrances. Many studies focused on non-Pt electrocatalysts to replace the Pt catalyst. However, the activity of non-Pt catalysts is not enough to substitute the Pt catalyst yet. In addition, the study of Pt alloy catalysts toward HER for improving the activity and stability is relatively a few, which could decrease the Pt usage in the electrode. In this study, Pt alloys with Sc and La were prepared to improve catalytic activity for HER. In addition, the effect of the composition of Sc and La in the ternary alloy on the activity and stability is investigated. Generally, Pt3La and Pt3Sc are known for improving electrocatalytic activities of Pt towards oxygen reduction reaction but have not been studied for HER activity. As rare-earth metals have extremely low reduction potentials and difficult to synthesize alloy catalysts, electron-beam (EB) radiation method was applied to prepare carbon-supported rare earth metal alloyed Pt catalysts. EB method is a simple and eco-friendly preparation method which can reduce even rare earth metals. XRD analysis indicated that Pt alloys and Pt/C were successfully synthesized by the EB method. Peak shifts of Pt alloys suggested the alloy between Pt and Sc or/and La is well formed due to lattice parameter changes. From the electrochemical evaluation, although the Pt3La/C showed the highest mass activity at 100mV overpotential, this catalyst resulted in the low stability under voltage cycling condition. On the other hand, Pt3Sc/C showed highly improved stability and showed no noticeable change after 3000 potential cycles. From this result, optimal ratios of Sc and La in ternary Pt alloy can be suggested. Finally, the Pt3Sc0.7La0.3/C catalyst resulted in both improvements of activity for HER and stability under voltage cycling, which implies the synergic effect of Sc and La. The research idea is interesting but the quality of abstract is unacceptably low due to poor language. Out of a total of 14 sentences, 7 (50%) contain language errors which make some of these sentences unclear. Phrases such as, "to replace or reduce Pt usages while remaining high HER performances",."very relatively rare", "it has low stability and easily corroded" do not belong to understandable English.