Photocatalytic overall water splitting under visible light enabled by a particulate conjugated polymer loaded with iridium

The production of hydrogen from water via solar water splitting is a potential method to overcome the intermittency of the Sun’s energy by storing it as a chemical fuel. Inorganic semiconductors have been studied extensively as photocatalysts for overall water splitting, but polymer photocatalysts are also receiving growing attention. So far, most studies involving organic polymers report hydrogen production with sacrificial electron donors, which is unsuitable for large-scale hydrogen energy production. Here we show that a linear conjugated polymer photocatalyst can be used for overall water splitting to produce stoichiometric amounts of H2 and O2. We studied a range of different metal co-catalysts in conjunction with the linear polymer photocatalyst, the homopolymer of dibenzo[b,d]thiophene sulfone (P10). Photocatalytic activity was observed for palladium/iridium oxide-loaded P10, while other co-catalysts resulted in materials that showed no activity for overall water splitting. The reaction conditions were further optimized and the overall water splitting using the IrO2-loaded P10 was found to proceed steadily for an extended period (>60 hours) after the system stabilized. These results demonstrate that conjugated polymers can act as single component photocatalytic systems for overall water splitting when loaded with suitable co-catalysts, albeit currently with low activities. Significantly, though, organic polymers can be designed to absorb a large fraction of the visible spectrum, which can be challenging with inorganic catalysts. Transient spectroscopy shows that the IrO2 co-catalyst plays an important role in the generation of the charge separated state required for water splitting, with evidence for fast hole transfer to the co-catalyst. This solid-state approach should be transferable to other polymer photocatalysts, allowing this field to move away from sacrificial hydrogen production towards overall water splitting.

Transformation of Triglycerides to Fatty Acid Methyl Esters with Hydrophilic Sulfonated Silica (SiO2-SO3H) as Catalyst and Quaternary Ammonium Salts in Toluene or DMSO

Triglycerides of waste cooking oil reacted with methanol in refluxing toluene to yield mixtures of diglycerides, monoglycerides and fatty acid methyl esters (FAMEs) in the presence of 20% (w/w) catalyst/oil using the hydrophilic sulfonated silica (SiO2-SO3H) catalyst alone or with the addition of 10% (w/w) co-catalyst/oil [(Bun4N)](BF4) or Aliquat 336]. The addition of the ammonium salts to the catalyst lead to a decrease in the amounts of diglycerides in the products, but the concentrations of monoglycerides increased. Mixtures of [(Bun4N)](BF4)/catalyst were superior to catalyst alone or Aliquat 336/catalyst for promoting the production of mixtures with high concentrations of FAMEs. The same experiments were repeated using DMSO as the solvent. The use of the more polar solvent resulted in excellent conversion of the triglycerides to FAME esters with all three-catalyst media. A simplified mechanism is presented to account for the experimental results.

Robust direct Z-scheme exciton transfer dynamics by architecting 3D BiOI MF-supported non-stoichiometric Cu0.75In0.25S NC nanocomposite for co-catalyst-free photocatalytic hydrogen evolution

Photon-assisted hydrogen evolution over a co-catalyst-free CIS–BOI composite abiding by the direct Z-scheme charge transfer mechanism.

Porous Organic Polymer Supported Pd/Cu Bimetallic Catalyst for Heterogeneous Oxidation of Alkynes to 1,2-Diketones

A porous organic polymer (POP-POPh3) was readily prepared by oxidation of POP-PPh3 with H2O2. After coordination with PdCl2 and co-catalyst of CuBr2 precursor, a Pd/Cu bimetals-loaded porous organic polymer (Pd/Cu@POP-POPh3)...

Development of dual-functional catalysis for hydrazine oxidation by an organic p–n bilayer through in situ formation of a silver co-catalyst

An organic p–n bilayer induced the catalysis for hydrazine oxidation both under irradiation and in the dark particularly when Ag particles were employed as co-catalyst.