Increased solar-driven chemical transformations through surface-induced benzoperylene aggregation in dye-sensitized photoanodes

The impact of benzo[ghi]perylenetriimide (BPTI) dye aggregation on the performance of photoelectrochemical devices was explored, through imide-substitution with either alkyl (BPTI-A, 2-ethylpropyl) or bulky aryl (BPTI-B, 2,6-diisopropylphenyl) moieties, to, respectively, enable or suppress aggregation. While both dyes demonstrated similar monomeric optoelectronic properties in solution, adsorption onto mesoporous SnO2 revealed different behavior, with BPTI-A forming aggregates via π-stacking and BPTI-B demonstrating reduced aggregation in the solid state. BPTI photoanodes were tested in dye-sensitized solar cells (DSSCs) before application to dye-sensitized photoelectrochemical cells (DSPECs) for Br2 production (a strong oxidant) coupled to H2 generation (a solar fuel). BPTI-A demonstrated a twofold higher dye loading of the SnO2 surface than BPTI-B, resulting in a fivefold enhancement to both photocurrent and Br2 production. The enhanced output of the photoelectrochemical systems (with respect to dye loading) was attributed to both J- and H- aggregation phenomena in BPTI-A photoanodes that lead to improved light harvesting. Our investigation provides a strategy to exploit self-assembly via aggregation to improve molecular light-harvesting and charge separation properties that can be directly applied to dye-sensitized photoelectrochemical devices.

Fabrication of a Novel Co/CoO@Fe2 V4 O13 Composite Catalyst as a Photoanode for Enhanced Photoelectrochemical Water Oxidation

Herein, the synthesis of a novel composite photocatalyst, Co/CoO@Fe2 V4 O13 , is reported by the deposition of CoO metal oxide nanoparticles on the surface of Fe2 V4 O13 bimetallic oxide. The synthesised photocatalyst exhibited a band gap of roughly 1.8 eV, rendering it responsive to the complete visible light spectrum of the sun, thereby enabling optimal absorption of solar radiation. The Co/CoO@Fe2 V4 O13 composites demonstrated an enhanced photoelectrochemical water oxidation capacity compared to pristine Fe2 V4 O13 when exposed to visible light. The enhanced performance is attributed primarily to the creation of a p-n junction at the interface of Fe2 V4 O13 and Co/CoO, as well as the Z-scheme charge transfer mechanism, which aids in the separation and transfer of photogenerated charge carriers. Light absorption by Co nanoparticles via plasmonic excitation and intra- and inter-band transitions in the composite structure is also likely, resulting in increased composite efficiency. Our findings indicate that Co/CoO@Fe2 V4 O13 composites show promising performance for solar water splitting applications and offer new perspectives for designing effective photocatalysts.

TiO2/AgO composites by one step photo reduction technique as electron transport layers (ETL) for dye-sensitized solar cells

Dye-sensitized solar cell's electron transport layer is responsible for transporting photo-generated electrons to the outer circuit. Utilizing localized surface plasmon resonance (SPR), light absorption could be enhanced to a greater degree, which can drive dye molecules to excited state more effectively than far-field light. In this work, TiO₂ nanoparticles were prepared by solvothermal method, and Ag nanoparticles were decorated over TiO₂ surface through photodeposition method. XRD data of the TiO₂ sample exhibits anatase phase and in the Ag nanoparticle decorated TiO₂ sample, peaks corresponding to (111) planes of Ag was observed. UV-Vis absorption analysis of the TiO₂ and Ag decorated TiO₂ samples showed absorption in the UV region for the TiO_2, and the SPR effect was detected for the Ag deposited TiO₂ samples. Ag nanoparticles decorated over TiO₂ was observed to be spherical in shape through the images from transmission electron microscope. Presence of both Ag and AgO in the prepared sample was revealed through the data from X-ray photoelectron spectroscopy. The prepared material was used as photoanodes in the construction of the DSSCs, and their performance was evaluated.

Fundamentals and applications of photoelectrocatalysis as an efficient process to remove pollutants from water: A review

Water pollution is an environmental problem in constant raising because of population growing, industrial development, agricultural frontier expansion, and principally because of the lack of wastewater treatment technology to remove organic recalcitrant and toxic pollutants from industrial and domestic wastewater. Recalcitrant compounds are a serious environmental and health problem mainly due to their toxicity and potential hazardous effects on living organisms, including human beings. Conventional wastewater treatments have not been able to remove efficiently pollutants from water; however, electrochemical advanced oxidation processes (EAOPs) are able to solve this environmental concern. One of the most recent EAOPs technology is photoelectrocatalysis (PEC), it consists in applying an external bias potential to a semiconductor film placed over a conductive substrate to avoid the recombination of photogenerated electron-hole (e^-/h⁺) pairs, increasing h⁺ availability and hydroxyl radicals' formation, responsible for promoting the degradation/mineralization of organic pollutants in aqueous medium. This review summarizes the recent advances in PEC as a promising technology for wastewater treatment. It addresses the fundamentals and kinetic aspects of PEC. An analysis of photoanode materials and of the configuration of photoelectrochemical reactors is also presented, including an analysis of the influence of the main operational parameters on the treatment of contaminated water. Finally, the most recent applications of PEC are reviewed, and the challenges and perspectives of PEC in wastewater treatment are discussed.

Surface sulfurization activating hematite nanorods for efficient photoelectrochemical water splitting

Surface treatment is an effective method to improve the photoelectrochemical (PEC) performance of photoelectrodes. Herein, we introduced a novel strategy of surface sulfurization to modify hematite (α-Fe₂O₃) nanorods grown in an aqueous solution, which triggered encouraging improvement in PEC performances. In comparison to the solution-grown pristine α-Fe₂O₃ nanorod photoanode that is PEC inefficient and always needs high temperature (>600 °C) activation, the surface sulfurized α-Fe₂O₃ nanorods show photocurrent density increased by orders of magnitude, reaching 0.46 mA cm^-2 at 1.23 V vs. RHE (reversible hydrogen electrode) under simulated solar illumination. This improvement in PEC performances should be attributed to the synergy of the increased carrier density, the reduced surface charge carrier recombination and the accelerated water oxidation kinetics at the α-Fe₂O₃/electrolyte interface, as induced by the incorporation of S ions and the formation of multi-state S species (Fe-S_x-O_y) at the surface of α-Fe₂O₃ nanorods. This study paves a new and facile approach to activate α-Fe₂O₃ and even other metal oxides as photoelectrodes for improved PEC water splitting performances, by engineering the surface structure to relieve the bottlenecks of charge transfer dynamics and redox reaction kinetics at the electrode/electrolyte interface.