Investigation of New Pt Alloy Catalyst with Rare Earth Elements for Hydrogen Evolution Reaction
Authors: Baik Chae kyung , Lee Seung Woo , Kim Mi So , Chai Geun Seok , Pak Chanho 
Published: February 2020

As rapid development of fuel cell and hydrogen industries are observed recently, necessity of hydrogen infrastructure of production and transportation emerged as the key. Because steam reforming and partial oxidation of hydrocarbons are main methods to produce hydrogen, water electrolysis should be studied and developed to accelerate hydrogen economy (1, 2). To become complete green energy, hydrogen production via water electrolysis is demanded in hydrogen economy. For developing hydrogen evolution reaction (HER) electrocatalysts, cheap, efficient and stable catalysts are essential for large-scale application. 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 or Pt alloy catalysts to replace or reduce Pt usages while remaining high HER performances (3, 4). Remarkable improvements were observed in such catalysts but synthesis of the catalysts are complex and difficult for large-scale applications (5).
In this study, platinum alloy with Sc and La were prepared to improve catalytic activities in HER. Pt3La and Pt3Sc are known and studied for improving electrocatalytic activities of Pt in oxygen reduction reaction (ORR) but have not been studied for HER activity (6). As rare-earth metals have extremely low reduction potentials and difficult to synthesize alloy catalysts, electron-beam(EB) radiation method was applied to synthesize carbon supported rare earth metal alloyed Pt catalyst. EB method is a simple and eco-friendly reduction method which can reduce even rare earth metals and also have advantages in mass production (7).
XRD analysis indicated that Pt alloys and Pt/C were successfully synthesized. Peak shifts were the evidences of the alloy formation due to lattice parameter changes. From the electrochemical evaluations, although Pt3La/C showed the highest mass activity at overpotential 100mV, it has low stability and easily corroded. On the other hand, Pt3Sc/C showed highly improved stability and showed no noticeable change after 3000 HER cycles. From this result, optimal ratios of Sc and La in Pt ternary alloy can be investigated and expected to have both high activity and stability.

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