Electrocatalytic properties of polymorphic Barium Ruthenate epitaxial thin films

Abstract

The applications of hydrogen have been received into the spotlight as a glob-al challenge for the development of renewable energy. Hydrogen evolution reac-tion (HER) by electrocatalysis is an important reaction, although the efficient generation of hydrogen is quite problematic. Therefore, HER catalysts with high activity, stability, and low cost are essential for various energy applications. BaRuO3 (BRO) has four different polymorphic crystal phases, including nine-layered rhombohedral (9R), six-layered hexagonal (6H), four-layered hexag-onal (4H), and three-layered cubic (3C). In this study, we prepared epitaxial thin films of 9R-BRO and 3C-BRO by pulsed laser deposition to study how crystal structure influences the electrocatalytic properties for HER. The structural charac-teristics of 9R- and 3C-BRO thin films were characterized by X-ray diffraction. The electrocatalytic properties of epitaxial BRO thin films based on crystal struc-tures were analyzed with the experiments. The 3C-BRO shows the enhanced per-formance of alkaline hydrogen evolution reactions compared to 9R-BRO with exhibiting an about 100 mV smaller overpotential to deliver a geometric current density of -10 mA/cm2. This study provides us a direction for searching the mech-anism of alkaline hydrogen evolution catalysts.