Improving Hydrogen Evolution Reaction Activity of Palladium By Ruthenium

Abstract

Hydrogen is one of the cleanest and most promising energy carriers that has all criteria considered for an alternative energy source. The hydrogen evolution reaction (HER) has been widely studied on noble metal catalysts, such as Pt and Pd owing to their extremely high activity in acid.1 However, these catalysts exhibit unexplained sluggish kinetics in alkaline media by orders of magnitude slower than that in acidic solutions.2-3 Here, we demonstrated that by conjunction with additional transition metal Ru, the activity of pure Pd can be enhanced. In this study, PdRu alloys with different composition ratios were synthesized by impregnation method and were heat treated under different temperatures in Ar atmosphere. Their HER activities were investigated in both 0.5M H2SO4 and 1M KOH solutions. By comparison, the surface-modified Pd with Ru adatoms (Pd@Ru) was also prepared. The alloy showed excellent catalytic activities for HER than Pd@Ru and Pd. In acid (Figure 1a), Pd3Ru exhibited 32 mV shift at 10 mA cm-2 compared with Pd. In an alkaline solution (Figure 1b), it showed even more remarkable enhancement, with 120 mV improvement at 10 mA cm-2. At high pH, it was even more active than Pt. Based on these observations, alloying with Ru can increase the HER activity significantly, especially in alkaline solutions. In this talk, the results of density functional theory (DFT) calculations will be also discussed. References (1) Durst, J.; Siebel, A.; Simon, C.; Hasche, F.; Herranz, J.; Gasteiger, H., Energy Environ. Sci. 2014, 7, 2255-2260. (2) Zheng, J.; Sheng, W.; Zhuang, Z.; Xu, B.; Yan, Y., Science advances 2016, 2, e1501602. (3) Strmcnik, D.; Uchimura, M.; Wang, C.; Subbaraman, R.; Danilovic, N.; van der Vliet, D.; Paulikas, A. P.; Stamenkovic, V. R.; Markovic, N. M., Nat. Chem. 2013, 5, 300-306. Figure 1