Visible light to switch-on desorption from goethite

Photo-Modulating CO2 Uptake of Hypercross-linked Polymers Upcycled from Polystyrene Waste

Incorporating photo-switches into skeletal structures of microporous materials or as guest molecules yield photo-responsive materials for low-energy CO₂ capture but at the expense of lower CO₂ uptake. Here, we overcome this limitation by exploiting trans-cis photoisomerization of azobenzene loaded into the micropores of hypercross-linked polymers (HCPs) derived from waste polystyrene. Azobenzene in HCP pores reduced CO₂ uptake by 19 %, reaching 37.7 cm³  g^-1 , but this loss in CO₂ uptake was not only recovered by trans-cis photoisomerization of azobenzene, but also increased by 22 %, reaching 56.9 cm³  g^-1 , when compared to as-prepared HCPs. Computational simulations show that this increase in CO₂ uptake is due to photo-controlled increments in 10-20 Å micropore volume, i. e., adsorption sites and a photo-reversible positive dipole moment. Irradiating these HCPs with visual-range light reverted CO₂ uptake to 33 cm³  g^-1 . This shows that it is feasible to recycle waste polystyrene into advanced materials for low-energy carbon capture.

Engineering Z-Scheme FeOOH/PCN with Fast Photoelectron Transfer and Surface Redox Kinetics for Efficient Solar-Driven CO2 Reduction

Solar-driven conversion of carbon dioxide (CO₂) without sacrificial agents offers an attractive alternative in sustainable energy research; nevertheless, it is often retarded by the sluggish water oxidation kinetics and severe charge recombination. To this end, a Z-scheme iron oxyhydroxide/polymeric carbon nitride (FeOOH/PCN) heterojunction, as identified by quasi in situ X-ray photoelectron spectroscopy, is constructed. In this heterostructure, the two-dimensional FeOOH nanorod provides rich coordinatively unsaturated sites and highly oxidative photoinduced holes to boost the sluggish water decomposition kinetics. Meanwhile, PCN acts as a robust agent for CO₂ reduction. Consequently, FeOOH/PCN achieves efficient CO₂ photoreduction with a superior selectivity of CH₄ (>85%), together with an apparent quantum efficiency of 2.4% at 420 nm that outperforms most two-step photosystems to date. This work offers an innovative strategy for the construction of photocatalytic systems toward solar fuel production.

Visible-Light Active Flexible and Durable Photocatalytic Antibacterial Ethylene-co-vinyl Acetate-Ag/AgCl/α-Fe2O3 Composite Coating

When particles are mixed in polymer, particle surfaces become passivated by polymer matrix, leading to significantly reduced photocatalytic and, thus, also reduced antibacterial activity, as the catalytic particles become isolated from the outer environment and microorganisms reaching the surface. Herein, we demonstrate a facile and rapid approach for coating preparation at room temperature, yielding good adhesion of particles in combination with the particles’ interface location. Flexible ethylene-co-vinyl acetate Ag/AgCl/α-Fe₂O₃ composite coatings were prepared by the spin-coating method. The synthesized photocatalytically active coating surface exhibited a distinct and rapid inhibition of bacterial growth, with at least a 7-log reduction of gram-positive bacteria Staphylococcus aureus viability after 30 min of visible-light illumination. We also analyzed the shedding of the Ag-ions and reactive oxygen species production from the composite coating and showed that reactive oxygen species played the main role in the photocatalytic bacterial inactivation, destroying the bacteria cell as proven by the Confocal Laser Scanning Microscopy.

Heterogeneous Fenton Degradation of Organic Pollutants in Water Enhanced by Combining Iron-type Layered Double Hydroxide and Sulfate

Water pollution derived from organic pollutants is one of the global environmental problems. The Fenton reaction using Fe²⁺ as a homogeneous catalyst has been known as one of clean methods for oxidative degradation of organic pollutants. Here, a layered double hydroxide (Fe²⁺ Al³⁺ -LDH) containing Fe²⁺ and Al³⁺ in the structure was used to develop a "heterogeneous" Fenton catalyst capable of mineralizing organic pollutants. We found that sulfate ion (SO₄ ^2- ) immobilized on the Fe²⁺ Al³⁺ -LDH significantly facilitated oxidative degradation (mineralization) of phenol as a model compound of water pollutants to carbon dioxide (CO₂ ) in a heterogeneous Fenton process. The phenol conversion and mineralization efficiency to CO₂ reached >99% and ca. 50%, respectively, even with a reaction time of only 60 min.

Identifying Iron-Bearing Nanoparticle Precursor for Thermal Transformation into the Highly Active Hematite Photo-Fenton Catalyst

The hematite photo-Fenton catalysis has attracted increasing attention because it offers strong oxidation of organic pollutants under visible light at neutral pH. In the present work, aqueous synthesis of hematite photo-Fenton catalysts with high activity is demonstrated. We compare photo-Fenton activity for hematite obtained by hydrolyzation at 60 °C or by a thermally induced transformation from iron-bearing nanoparticles, such as amorphous iron oxyhydroxide or goethite. A link between their structure and visible light photo-Fenton reactivity is established. The highest activity was observed for hematite obtained from goethite nanowires due to oblong platelet-like structure, high surface area and the presence of nanopores.