Hydrogen production from the decomposition of methanol on Ir(100) and O-Ir(100) surfaces

Yu-Yao Hsia^1*, Yu-Ling Lai², Yao-Jane Hsu², Meng-Fan Luo¹

¹Department of Physics, National Central University, Taoyuan, Taiwan
²National Synchrotron Radiation Research Center, Hsinchu Science Park, Hsinchu, Taiwan

* Presenter:Yu-Yao Hsia, email:siab1144775@gmail.com

To reach the worldwide goal of carbon net-zero emission, the feasible generation of hydrogen from the methanol decomposition has been considered as an alternative clean energy source. Surface atomic oxygen (O*) plays a crucial role in methanol decomposition on transition metal surfaces, since O* can enhance the reaction probabilities and yield high production of hydrogen. For instance, O* on Cu(110) induce (2 × 1) reconstruction but only the terminal O* in the O* chains is reactive in the methanol decomposition [1, 2]. The interaction of O* with supporting metal surfaces could alter their electronic properties and thus activity, so O* could exhibit varied activities on transition metals. The decomposition of methanol on various transition metals, including Pt, Pd, Cu, and Rh, has been extensively studied; nevertheless, the methanol reaction on Ir surfaces is little explored and the activity of O* on them is also little known. We herein present out investigation of catalyzed reaction of methanol on Ir(100) and atomic oxygen pre-adsorbed Ir(100) (denoted as O-Ir(100)) surfaces under ultrahigh-vacuum (UHV) conditions and with various techniques to probe the surface, such as TPD and synchrotron-based PES. The adsorbed methanol decomposes on O*-free surface through two channels – dehydrogenation to CO* and C-O bond scission of methanol, and ultimately produces gaseous CO, H2, and atomic carbons. The reaction probability of monolayer methanol on Ir(100) reaches 60%, notably great than that on Pt and Pd single crystals. The O* facilitated the scission of O-H bond scission of methanol in the initial dehydrogenation of the adsorbed methanol and forming hydroxyl (OH*) and methoxy (CH3O*). The formation of CH3O* suppressed the channel of C-O bond scission and promoted the reaction probability from 60% to nearly 100%. With the presence of O* (around 0.3 ML), the production of hydrogen can be enhanced to nearly 70%.

[1] P.R. Davies and G.G. Mariotti, J. Phys. Chem. 1996, 100, 19975 – 19980.
[2] P.R. Davies and M. Bowker, Catalysis Today 154 (2010) 31–37.

Keywords: Hydorgen production, Methanol decomposition, Ir(100)