Proton-assisted electron transfer and hydrogen-atom diffusion in a model system for photocatalytic hydrogen production

Abstract

Solar energy can be converted into chemical energy by photocatalytic water splitting to produce molecular hydrogen. Details of the photo-induced reaction mechanism occurring on the surface of a semiconductor are not fully understood, however. Herein, we employ a model photocatalytic system consisting of single atoms deposited on quantum dots that are anchored on to a primary photocatalyst to explore fundamental aspects of photolytic hydrogen generation. Single platinum atoms (Pt1) are anchored onto carbon nitride quantum dots (CNQDs), which are loaded onto graphitic carbon nitride nanosheets (CNS), forming a Pt1@CNQDs/CNS composite. Pt1@CNQDs/CNS provides a well-defined photocatalytic system in which the electron and proton transfer processes that lead to the formation of hydrogen gas can be investigated. Results suggest that hydrogen bonding between hydrophilic surface groups of the CNQDs and interfacial water molecules facilitates both proton-assisted electron transfer and sorption/desorption pathways. Surface bound hydrogen atoms appear to diffuse from CNQDs surface sites to the deposited Pt1 catalytic sites leading to higher hydrogen-atom fugacity surrounding each isolated Pt1 site. We identify a pathway that allows for hydrogen-atom recombination into molecular hydrogen and eventually to hydrogen bubble evolution.

Advances in organic semiconductors for photocatalytic hydrogen evolution reaction

“…In one scenario, the undissociated exciton reaches the interface between the photocatalyst and water. The hole in the exciton is captured by the absorbed H 2 O/sacrificial donor, while the electron is separated and used to reduce the reductive adsorbed proton 61 . Alternatively, the excitons are separated into electrons and holes in the bulk of photocatalyst.…”

“…The hole in the exciton is captured by the absorbed H 2 O/ sacrificial donor, while the electron is separated and used to reduce the reductive adsorbed proton. 61 Alternatively, the excitons are separated into electrons and holes in the bulk of photocatalyst. The electrons then arrive at the surface and reduce the adsorbed protons.…”

Mid‐IR Light‐Activatable Full Spectrum LaB6 Plasmonic Photocatalyst

“…The EPR patterns of both hydrogen and hydroxyl radicals also match well with those literature-reported spectra. [20][21][22][23] In the presence of a hydroxyl radical specific quencher, that is, mannitol, the hydroxyl radical EPR signals were significantly suppressed, but not the hydrogen radical signal (see Figure S4, Supporting Information). Upon prolonged MIR (3900 nm) light irradiation, the hydrogen radical signals gradually disappear and hydroxyl radicals dominate in the EPR spectra.…”

Targeted Antibacterial Strategy Based on Reactive Oxygen Species Generated from Dioxygen Reduction Using an Organoruthenium Complex

“…Spin-trapped H • observed was likely owing to the SET of Ru1 to protons in the analyzed solutions. 50,51 Taken together, we posited that Ru1 could generate ROS from multiple pathways, via either TFH of O 2 from a Ru−H intermediate or direct O 2 reduction through electron transfer (Figure S9).…”

“…We attributed • CH 2 OH to H atom abstraction on MeOH by HO • , arising from the well-documented degeneration of O 2 •– in water. , Because these species only occurred in the presence of both Ru1 and O 2 , we surmised that this was due to O 2 •– formation via Ru1-induced SET on O 2 . Spin-trapped H • observed was likely owing to the SET of Ru1 to protons in the analyzed solutions. , Taken together, we posited that Ru1 could generate ROS from multiple pathways, via either TFH of O 2 from a Ru–H intermediate or direct O 2 reduction through electron transfer (Figure S9).…”