ON-OFF Switching of Photocatalytic Hydrogen Evolution by Built-in Pt-Nitrogen-Carbon Reticular Heterojunctions.

COF engineering with a built-in, high concentration of defined N-doped sites overcomes the "black-box" drawback of conventional trial-and-error N-doping methods (used in polymeric carbon nitride and graphene), that hamper a directed evolution of functional carbon interfaces based on structure-reactivity guidelines. The cutting-edge challenge is to dissect the many complex and interdependent functions that originate from reticular N-doping, including modification of the material optoelectronics, band alignments, interfacial contacts and co-localization of active-sites, producing a multiple-set of effectors that can all play a role to regulate photocatalysis. Herein, an ON-OFF gated photocatalytic H evolution (PHE) is dictated by the Pt-N-carbon active sites and probed with a dual COF platform, based on stable β-ketoenamine connectivities made of triformylphloroglucinol (Tp) as the acceptor knots and 1,4-diaminonaphtalene (Naph) or 5,8-diaminoisoquinoline (IsoQ) as donors.

Role of Intragap States in Sensitized Sb-Doped Tin Oxide Photoanodes for Solar Fuels Production.

In view of developing photoelectrosynthetic cells which are able to store solar energy in chemical bonds, water splitting is usually the reaction of choice when targeting hydrogen production. However, alternative approaches can be considered, aimed at substituting the anodic reaction of water oxidation with more commercially capitalizable oxidations. Among them, the production of bromine from bromide ions was investigated long back in the 1980s by Texas Instruments.

Combined Covalent and Supramolecular Polymerization to Reinforce Perylenebisimide Photosynthetic "Quantasomes".

PSII-inspired quantasomes have emerged as promising artificial photosystems evolving oxygen from water due to their integrated multi-chromophore asset, hierarchical architecture, and efficient light-harvesting capabilities. In this study, we adopt a combined covalent and supramolecular strategy by implementing a poly-styrene backbone that reinforces proximity and pairing between adjacent perylenebisimide (PBI) quantasome units. The covalent fixation of the quantasome network results in a significant enhancement of the photoelectrocatalytic performance on engineered IO-ITO photoanodes, with up to 290 % photocurrent increase (J up to 100 μA cm, λ >450 nm, applied bias <1.

A breath of sunshine: oxygenic photosynthesis by functional molecular architectures.

The conversion of light into chemical energy is the game-changer enabling technology for the energetic transition to renewable and clean solar fuels. The photochemistry of interest includes the overall reductive/oxidative splitting of water into hydrogen and oxygen and alternatives based on the reductive conversion of carbon dioxide or nitrogen, as primary sources of energy-rich products. Devices capable of performing such transformations are based on the integration of three sequential core functions: light absorption, photo-induced charge separation, and the photo-activated breaking/making of molecular bonds specific catalytic routes.

Enhancing Oxygenic Photosynthesis by Cross-Linked Perylenebisimide "Quantasomes".

As the natural-born photoelectrolyzer for oxygen delivery, photosystem II (PSII) is hardly replicated with man-made constructs. However, building on the "quantasome" hypothesis ( 1964, 144, 1009-1011), PSII mimicry can be pared down to essentials by shaping a photocatalytic ensemble (from the Greek term "soma" = body) where visible-light quanta trigger water oxidation. PSII-inspired quantasomes (QS) readily self-assemble into hierarchical photosynthetic nanostacks, made of bis-cationic perylenebisimides (PBI) as chromophores and deca-anionic tetraruthenate polyoxometalates (RuPOM) as water oxidation catalysts ( 2019, 11, 146-153).

Photoanodes for water oxidation with visible light based on a pentacyclic quinoid organic dye enabling proton-coupled electron transfer.

A pentacyclic quinoid dye, KuQ(O)3OH, combining (i) extended visible absorption up to 600 nm, (ii) excited state reduction potential >2 V vs. NHE, and (iii) a photoinduced proton-coupled electron transfer mechanism, has been used for the fabrication of dye-sensitized SnO2 photoanodes integrating a ruthenium polyoxometalate water oxidation catalyst. The resulting photoelectrode SnO2|KuQ(O)3OH|Ru4POM displays a light harvesting efficiency up to 90% in the range 500-600 nm, an onset potential as low as 0.