Photochemical Hydrogenation of CO₂ to CH₃OH and Pyridine to 1,2-Dihydropyridine Using Plasmon-Facilitated Chemisorbed Hydrogen on Au Surface: Theoretical Perspective

Abstract

CO2 hydrogenation to methanol, a renewable fuel, under benign conditions and without the use of sacrificial agents is a rarity and certainly a much sought after goal of present-day research. Herein, we report using well calibrated computational tools the viability of hydrogenating CO2 to CH3OH and pyridine to 1,2-dihydropyridine, a renewable organohydride which can also reduce CO2 to CH3OH sustainably, using hydrogens chemisorbed on Au(111) surface of Au20 by photo-excitation. Our studies predict that these hydrogenations can occur at appreciable rates at room temperature. Thus, we reveal the untapped potential of the chemisorbed hydrogens on Au(111) surface, achieved by hot-electron generation through photo-excitation, in facilitating endoergic hydrogenations akin to those enabled by NADPH.

Exploring the Crucial Role of Solvation on the Viability of Sustainable Hydrogen Storage in BN-fullerene: A Combined DFT and Ab Initio Molecular Dynamics Investigation

“…Recently, we have shown that this endoergic hydrogenation of pyridine to get 1,2PyH 2 is possible via purely photolytic means. 3 Hydrogenation of (micro)solvated (BN) 24 is more thermodynamically demanding, and we anticipate that 1,2PyH 2 can drive that hydrogenation in a more exoergic fashion. The thermodynamics of the overall reaction ((BN) 24 {THF} 8 + 16PyH 2 → (BN) 24 (H) 32 + 16Py + 8THF) was estimated to be −106.8 kcal mol −1 : i.e., −6.7 kcal mol −1 per hydrogenation.…”

“…3,46−48 1,2PyH 2 is one of the most important organohydrides. 3,46,47 Please note that, just as for i Pr 2 HN−BH 3 , 1,2PyH 2 also contains both protic and hydridic hydrogens (the C−H hydrogen is hydridic in nature, whereas the N−H hydrogen is protic in nature). 3,46,47 Most importantly, the hydrogenation thermodynamics of pyridine with molecular H 2 (g) to get 1,2PyH 2 turned out to be +14.4 kcal mol −1 at the M062X/6-311++G(d,p) level of theory.…”

“…2 In this context, it is worth mentioning that, in another recent work, we have proposed that pyridine can be reduced to generate 1,2PyH 2 using photochemically chemisorbed hydrogens on a Au(111) surface, thus making the process sustainable. 3 BN-fullerenes are composed of tetragonal, hexagonal, and octagonal BN rings. It should be noted that the presence of high curvature with eight strained tetragonal B 2 N 2 rings makes hydrogenation favorable in (BN) 24 in comparison to that of other BN materials.…”

Plasmonic photocatalysis applied to solar fuels

“…Molecular hydrogen is indeed known to readily dissociate over plasmon-activated Au NPs. 15,40,43 Hence, even if it was formed in the present water-mediated CO2 photoreduction process, it would not be stable. One may also speculate that it may simply not be formed as it is in the SC-based process and that H ○ + H ○ recombination simply does not occur in the gold-driven, plasmon-based process.…”

The curious saga of dehydrogenation/hydrogenation for chemical hydrogen storage: a mechanistic perspective

“…5 Hence, contemporary research in this area has explored alternative options, such as using HCOOH and CH 3 OH as a vector for H 2 delivery. 6 Another route which is slowly unfolding as a probable avenue is the development of liquid organic hydrogen carriers. 7 These are organic molecules which can be catalytically dehydrogenated for H 2 release, but most importantly the dehydrogenated spent fuel can be hydrogenated conveniently.…”