Indole derivatives are considered as promising liquid organic hydrogen carriers for renewable energy storage. Using X-ray photoelectron spectroscopy, temperature-programmed desorption, and infrared reflection–absorption spectroscopy, we investigated low-temperature adsorption and dehydrogenation during heating of indole, indoline, and octahydroindole on Pt(111). For all three molecules, we find deprotonation of the NH bond above 270 K, accompanied with dehydrogenation of indoline and octahydroindole via an indole intermediate, resulting in an indolide species above 300 K. For octahydroindole, we also find a side reaction yielding small amounts of a π-allyl species between 170 and 450 K. Above 450 K, decomposition of the remaining indolide species takes place.

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Indole derivatives were recently proposed as potential liquid organic hydrogen carriers (LOHC) for storage of renewable energies. In this work, we have investigated the adsorption, dehydrogenation and degradation mechanisms in the indole/indoline/octahydroindole system on Pt(111). We have combined infrared reflection absorption spectroscopy (IRAS), X-ray photoelectron spectroscopy (XPS) and DFT calculations. Indole multilayers show a crystallization transition at 200 K, in which the molecules adopt a strongly tilted orientation, before the multilayer desorbs at 220 K. For indoline, a less pronounced restructuring transition occurs at 150 K and multilayer desorption is observed at 200 K. Octahydroindole multilayers desorb already at 185 K, without any indication for restructuring. Adsorbed monolayers of all three compounds are stable up to room temperature and undergo deprotonation at the NH bond above 300 K. For indoline, the reaction is followed by partial dehydrogenation at the 5-membered ring, leading to the formation of a flat-lying di-σ-indolide in the temperature range from 330-390 K. Noteworthy, the same surface intermediate is formed from indole. In contrast, the reaction of octahydroindole with Pt(111) leads to the formation of a different intermediate, which originates from partial dehydrogenation of the 6-membered ring. Above 390 K, all three compounds again form the same strongly dehydrogenated and partially decomposed surface species.

The interaction of single-layer hexagonal boron nitride (h-BN) on Ni(111)w ith molecular oxygen from as upersonic molecular beam led to ac ovalently bonded molecular oxygen species, which was identified as being between as uperoxide and aperoxide. This is arareexample of an activated adsorption process leadingt oam olecular adsorbate. The amount of oxygen functionalization depended on the kinetic energy of the molecular beam.F or ak inetic energy of 0.7 eV,a no xygen coverage of 0.4 ML was found. Near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy revealed as tronger bond of h-BN to the Ni(111)s ubstrate in [a] Dr.

Dwindling fossil fuels force humanity to search for new energy production routes. Besides energy generation, its storage is a crucial aspect. One promising approach is to store energy from the sun chemically in strained organic molecules, so-called molecular solar thermal (MOST) systems, which can release the stored energy catalytically. A prototypical MOST system is norbornadiene/quadricyclane (NBD/QC) whose energy release and surface chemistry need to be understood. Besides important key parameters such as molecular weight, endergonic reaction profiles, and sufficient quantum yields, the position of the absorption onset of NBD is crucial to cover preferably a large range of sunlight’s spectrum. For this purpose, one typically derivatizes NBD with electron-donating and/or electron-accepting substituents. To keep the model system simple enough to be investigated with photoemission techniques, we introduced bromine atoms at the 2,3-position of both compounds. We study the adsorption behavior, energy release, and surface chemistry on Ni(111) using high-resolution X-ray photoelectron spectroscopy (HR-XPS), UV photoelectron spectroscopy, and density functional theory calculations. Both Br2-NBD and Br2-QC partially dissociate on the surface at ∼120 K, with Br2-QC being more stable. Several stable adsorption geometries for intact and dissociated species were calculated, and the most stable structures are determined for both molecules. By temperature-programmed HR-XPS, we were able to observe the conversion of Br2-QC to Br2-NBD in situ at 170 K. The decomposition of Br2-NBD starts at 190 K when C–Br bond cleavage occurs and benzene and methylidene are formed. For Br2-QC, the cleavage already occurs at 130 K when cycloreversion to Br2-NBD sets in.