Hydrogen‐Bonded Organic Semiconductors as Stable Photoelectrocatalysts for Efficient Hydrogen Peroxide Photosynthesis

Abstract

Research on semiconductor photocatalysts for the conversion of solar energy into chemical fuels has been at the forefront of renewable energy technologies. Water splitting to produce H2 and CO2 reduction to hydrocarbons are the two prominent approaches. A lesser‐known process, the conversion of solar energy into the versatile high‐energy product H2O2 via reduction of O2 has been proposed as an alternative concept. Semiconductor photoelectrodes for the direct photosynthesis of H2O2 from O2 have not been applied up to now. Photoelectrocatalytic oxygen reduction to peroxides in aqueous electrolytes by hydrogen‐bonded organic semiconductor is observed photoelectrodes. These materials have been found to be remarkably stable operating in a photoelectrochemical cell converting light into H2O2 under constant illumination for at least several days, functioning in a pH range from 1 to 12. This is the first report of a semiconductor photoelectrode for H2O2 production, with catalytic performance exceeding prior reports on photocatalysts by one to two orders of magnitude in terms of peroxide yield/catalyst amount/time. The combination of a strongly reducing conduction band energy level with stability in aqueous electrolytes opens new avenues for this widely available materials class in the field of photo(electro) catalysis.

Cellular interfaces with hydrogen-bonded organic semiconductor hierarchical nanocrystals

“…The hydrogen-bonded pigment QNC is particularly interesting in the context of biological applications due to reported nontoxicity 46 and presence of NH functional groups that enable direct bioconjugation reactions 47 . Recently QNC, in the form of vacuum-evaporated thin films, has been reported as a promising semiconductor, with outstanding stability, ambipolar charge carrier mobility, and favourable optoelectronic 48 and photocatalytic 49 properties. The multifunctionality and availability of QNC make it a good target for making organic semiconducting hierarchical nanostructures.…”

Aqueous photo(electro)catalysis with eumelanin thin films

“…It has been recently demonstrated that some organic semiconducting small molecules can act as aqueous photocatalysts 28,29 or photoelectrocatalysts 30,31 32,33 inspiring detailed investigation into the role of eumelanin interactions with reactive oxygen species (ROS). In his 1990 paper, Sarna noted that the molar quantity of H 2 O 2 produced during the photochemical degradation of eumelanin was 20% higher than the molar equivalent of the starting monomers.…”

Water‐Soluble Organic Dyes as Molecular Photocatalysts for H2O2 Evolution

“…[14,16] The molecular dye derivatives here, however, generate peroxide more efficiently under neutral to basic pH conditions. Irradiation of solutions without dye does not produce any H 2 O 2 , just as dye solutions in the dark do not produce H 2 O 2 .…”

“…We synthesized three compounds shown in Figure 1b. [16] As a water-soluble analog to the proven photo and electrocatalyst, [14,20] perylenetetracarboxylic-3,4,9,10-diimide (PTCDI), we synthesized a derivative bearing two sulfonic acid-terminated groups: [16] As a water-soluble analog to the proven photo and electrocatalyst, [14,20] perylenetetracarboxylic-3,4,9,10-diimide (PTCDI), we synthesized a derivative bearing two sulfonic acid-terminated groups:…”

“…The cornerstone in the peroxide energy cycle is photogeneration via a catalyzed reaction of solar irradiation with oxygen and water. [16][17][18] On the other hand, a fundamental obstacle in all these examples is related to the fact that only the surface of the particle, exposed to the electrolyte, can actively participate in the photo(electro) catalytic process. Photocatalysts are used in the form of suspensions of particles varying in size from tens of micrometers to a few nanometers.…”