Visible-light photocatalytic hydrogen production from ethanol–water mixtures using a Pt–CdS–TiO2 photocatalyst

Optimizing Carbon Dot-TiO2 Nanohybrids for Enhanced Photocatalytic Hydrogen Evolution

CDs/TiO2 nanohybrids were synthesized and tested for photocatalytic H2 production from aqueous media through simulated solar light-driven photocatalytic reactions. Firstly, three different types of CDs were prepared through green methods, specifically hydrothermal treatment and microwave irradiation, using citric acid and urea as precursors in varying molar ratios. After a multi-step purification procedure, impurity-free CDs were obtained. The as-synthesized CDs were thoroughly characterized using UV-Vis, FT-IR, and PL spectroscopy, along with HR-TEM. The results revealed that the size and optical and physicochemical properties of CDs can be tailored by selecting the precursors' ratio and the synthetic approach. The heterostructured CDs/TiO2 photocatalysts were formed solvothermally and were analyzed using UV-Vis/DRS, FT-IR, and XPS techniques, which confirmed the effective incorporation of CDs and the improved properties of TiO2. The use of sacrificial reagents is among the most common strategies for enhancing H2 production from water through photocatalytic processes; herein, ethanol was selected as a green liquid organic hydrogen carrier. A maximum H2 production rate of 0.906 μmol H2/min was achieved, while the recyclability study demonstrated that the photocatalyst maintained stable performance during multiple cycles of reuse. Thus, optimizing the synthesis conditions of CDs/TiO2 nanohybrids resulted in the creation of environmentally friendly and reusable photocatalysts.

Study on the preparation of CdS/TiO2 corn straw biochar composite materials for photocatalytic reduction of CO2 and collaborative H2 production

A thermal synthesis method was employed in this work to prepare CdS/TiO2 corn straw biochar photocatalytic composite materials suitable for synergistic hydrogen production with the photocatalytic reduction of CO2. The structure and synergistic reaction of these composite materials were characterized by its photogenerated electron transfer process. Compared with pure TiO2, the energy band gap of the optimal CdS/TiO2 corn straw biochar composite material was reduced to 2.89 eV. The heterostructure coupling between TiO2 and CdS in the biochar accelerated the transfer of photogenerated electrons and reduced the recombination rate of photogenerated electrons and holes. Under visible light irradiation, the photocatalytic H2 yield of this CdS/TiO2 corn straw-derived biochar composite material was 1200 µmol·h-1·g-1, the CO yield was 150 µmol·h-1·g-1, and the CH4 yield was 55 µmol·h-1·g-1. The key to this synergistic reaction is the formation of heterojunctions between CdS and TiO2 as well as the rapid oxidation of holes in the composite material caused by the doping of biochar.

Cu2O/CuS/ZnS Nanocomposite Boosts Blue LED-Light-Driven Photocatalytic Hydrogen Evolution

In the present work, we described the synthesis and characterization of the ternary Cu2O/CuS/ZnS nanocomposite using a facile two-step wet chemical method for blue LED-light-induced photocatalytic hydrogen production. The concentrations of the ZnS precursor and reaction time were essential in controlling the photocatalytic hydrogen production efficiency of the Cu2O/CuS/ZnS nanocomposite under blue LED light irradiation. The optimized Cu2O/CuS/ZnS nanocomposite exhibited a maximum photocatalytic hydrogen evolution rate of 1109 µmolh−1g−1, which was remarkably higher than Cu2O nanostructures. Through the cycle stability it can be observed that the hydrogen production rate of the Cu2O/CuS/ZnS nanocomposite decreased after 4 cycles (1 cycle = 3 h), but it remained at 82.2% of the initial performance under blue LED light irradiation. These reasons are mainly attributed to the introduction of CuS and ZnS to construct a rationally coupled reaction system, which enables the synergistic utilization of photogenerated carriers and the increased absorption of visible light for boosting blue LED-light-driven photocatalytic hydrogen evolution.

Graphitic carbon nitride synthesized by simple pyrolysis: role of precursor in photocatalytic hydrogen production

g-C₃N₄ with structural defects and low polymerization synthesized by urea as the precursor for photocatalytic H₂ production under visible light.

Enhancement of simultaneous batik wastewater treatment and electricity generation in photocatalytic fuel cell

The objective of this study was to investigate several operating parameters, such as open circuit, different external resistance, pH, supporting electrolyte, and presence of aeration that might enhance the degradation rate as well as electricity generation of batik wastewater in solar photocatalytic fuel cell (PFC). The optimum degradation of batik wastewater was at pH 9 with external resistor 250 Ω. It was observed that open circuit of PFC showed only 17.2 ± 7.5% of removal efficiency, meanwhile the degradation rate of batik wastewater was enhanced to 31.9 ± 15.0% for closed circuit with external resistor 250 Ω. The decolorization of batik wastewater in the absence of photocatalyst due to the absorption of light irradiation by dye molecules and this process was known as photolysis. The degradation of batik wastewater increased as the external resistor value decreased. In addition, the degradation rate of batik wastewater also increased at pH 9 which was 74.4 ± 34.9% and at pH 3, its degradation rate was reduced to 19.4 ± 8.7%. The presence of aeration and sodium chloride as supporting electrolyte in batik wastewater also affected its degradation and electricity generation. The maximum absorbance of wavelength (λ_max) of batik wastewater at 535 nm and chemical oxygen demand gradually decreased as increased in irradiation time; however, batik wastewater required prolonged irradiation time to fully degrade and mineralize in PFC system.

Enhanced organic pollutants degradation and electricity production simultaneously via strengthening the radicals reaction in a novel Fenton-photocatalytic fuel cell system

An enhanced result in organic pollutants degradation and simultaneous electricity production has been achieved by establishing a novel Fenton-photocatalytic fuel cell (Fenton-PFC) system in which TiO₂ nanotube arrays (TNA) was designed as a photoanode and ferrous ions were added. The proposed Fenton-PFC system can expand the radical reaction for organic pollutants degradation from the surface of electrodes to the whole solution system due to a continuous photoelectric Fenton reaction without continually adding any external voltage and ferrous ions. The cyclic reactions between ferrous ions (Fe²⁺/Fe³⁺) and radicals and related species (HO, HO₂, O₂^- and H₂O₂ etc.) can be achieved at electrodes surface via a self-bias voltage yielded by the PFC. More importantly, the proposed Fenton-PFC system has hardly any sludge due to an effective radical reaction using a small amount of ferrous ions. The degradation rate of refractory organics, such as methyl orange, methylene blue, congo red and tetracycline, increased from 34.99%, 43.75%, 40.58% and 34.40% (the traditional PFC without Fe²⁺) to 97.34%, 95.36%, 93.23% and 73.80% (the Fenton-PFC within Fe²⁺) respectively after 60 min operation. Meanwhile, the electricity generation is up to 1.21-2.04 times larger than the traditional PFC. The proposed Fenton-PFC system provides a more economical and efficient way for energy recovery and wastewater treatment.

Catalytic selectivity of Rh/TiO2catalyst in syngas conversion to ethanol: probing into the mechanism and functions of TiO2support and promoter

The catalytic selectivity, the functions of a TiO₂support and promoter, and the mechanism of ethanol synthesis from syngas on a Rh/TiO₂model catalyst have been fully identified.

Structural design of TiO2-based photocatalyst for H2 production and degradation applications

This review aims to provide a comprehensive and contemporary overview, as well as a guide of the development of new generation TiO₂ based photocatalysts via structural design for improved solar energy conversion technologies.

Photocatalysis for renewable energy production using PhotoFuelCells

The present work is a short review of our recent studies on PhotoFuelCells, that is, photoelectrochemical cells which consume a fuel to produce electricity or hydrogen, and presents some unpublished data concerning both electricity and hydrogen production. PhotoFuelCells have been constructed using nanoparticulate titania photoanodes and various cathode electrodes bearing a few different types of electrocatalyst. In the case where the cell functioned with an aerated cathode, the cathode electrode was made of carbon cloth carrying a carbon paste made of carbon black and dispersed Pt nanoparticles. When the cell was operated in the absence of oxygen, the electrocatalyst was deposited on an FTO slide using a special commercial carbon paste, which was again enriched with Pt nanoparticles. Mixing of Pt with carbon paste decreased the quantity of Pt necessary to act as electrocatalyst. PhotoFuelCells can produce electricity without bias and with relatively high open-circuit voltage when they function in the presence of fuel and with an aerated cathode. In that case, titania can be sensitized in the visible region by CdS quantum dots. In the present work, CdS was deposited by the SILAR method. Other metal chalcogenides are not functional as sensitizers because the combined photoanode in their presence does not have enough oxidative power to oxidize the fuel. Concerning hydrogen production, it was found that it is difficult to produce hydrogen in an alkaline environment even under bias, however, this is still possible if losses are minimized. One way to limit losses is to short-circuit anode and cathode electrode and put them close together. This is achieved in the “photoelectrocatalytic leaf”, which was presently demonstrated capable of producing hydrogen even in a strongly alkaline environment.

Visible-light responsive photocatalytic fuel cell based on WO(3)/W photoanode and Cu(2)O/Cu photocathode for simultaneous wastewater treatment and electricity generation

A visible-light driven photocatalytic fuel cell (PFC) system comprised of WO(3)/W photoanode and Cu(2)O/Cu photocathode was established for organic compounds degradation with simultaneous electricity generation. The central idea for its operation is the mismatched Fermi levels between the two photoelectrodes. Under light illumination, the Fermi level of WO(3)/W photoanode is higher than that of Cu(2)O/Cu photocathode. An interior bias can be produced based on which the electrons of WO(3)/W photoanode can transfer from the external circuit to combine with the holes of Cu(2)O/Cu photocathode then generates the electricity. In this manner, the electron/hole pairs separations at two photoelectrodes are facilitated to release the holes of WO(3)/W photoanode and electrons of Cu(2)O/Cu photocathode. Organic compounds can be decomposed by the holes of WO(3)/W photoanode due to its high oxidation power (+3.1-3.2 V(NHE)). The results demonstrated that various model compounds including phenol, Rhodamine B, and Congo red can be successfully decomposed in this PFC system, with the degradation rate after 5 h operation were obtained to be 58%, 63%, and 74%, respectively. The consistent operation for continuous water treatment with the electricity generation at a long time scale was also confirmed from the result. The proposed PFC system provides a self-sustained and energy-saving way for simultaneous wastewater treatment and energy recovery.

Hierarchical TiO2/CdS "spindle-like" composite with high photodegradation and antibacterial capability under visible light irradiation

Novel hierarchical TiO(2)/CdS "spindle-like" composites with uniform distribution of CdS nanocrystals on nanoporous TiO(2) mesocrystals were successfully prepared by hydrothermal and hot-injection methods. In this work, the optimal mass ratio of Ti/Cd is determined to be 2 of as-synthesized TiO(2)/CdS composites. This TiO(2)/CdS composite exhibits excellent photocatalytic activity in the degradation of Rhodamine B (RhB) and photocatalytic reaction constant is 10 times higher than that of TiO(2), 3.5 times higher than that of CdS and higher than other TiO(2)/CdS composites with different amount of Ti/Cd mass ratio. In addition, TiO(2)/CdS with optimal amount of CdS kills 99.9% of Escherichia coli in 10 min under visible-light irradiation, which shows significant higher efficiency than pure TiO(2), CdS and other TiO(2)/CdS composites. The excellent performances of this hierarchical composite are ascribed to its outstanding properties, including large specific surface area (BET), high crystallinity of oriented single-crystal-like nanoporous TiO(2) mesocrystals for charge transfer, retarded recombination of photogenerated electron-hole pairs via isolating electrons and holes in two different materials, and extended photo response of this hierarchical composite to the visible region. Considering all these superior properties and abilities, this hierarchical TiO(2)/CdS "spindle-like" composite will show great potential for applications in the water purification field.

Efficient electricity production and simultaneously wastewater treatment via a high-performance photocatalytic fuel cell

A great quantity of wastewater were discharged into water body, causing serious environmental pollution. Meanwhile, the organic compounds in wastewater are important sources of energy. In this work, a high-performance short TiO(2) nanotube array (STNA) electrode was applied as photoanode material in a novel photocatalytic fuel cell (PFC) system for electricity production and simultaneously wastewater treatment. The results of current work demonstrate that various model compounds as well as real wastewater samples can be used as substrates for the PFC system. As a representative of model compounds, the acetic acid solution produces the highest cell performance with short-circuit current density 1.42 mA cm(-2), open-circuit voltage 1.48 V and maximum power density output 0.67 mW cm(-2). The STNA photoanode reveals obviously enhanced cell performance compared with TiO(2) nanoparticulate film electrode or other long nanotubes electrode. Moreover, the photoanode material, electrolyte concentration, pH of the initial solution, and cathode material were found to be important factors influencing the system performance of PFC. Therefore, the proposed fuel cell system provides a novel way of energy conversion and effective disposal mode of organics and serves well as a promising technology for wastewater treatment.

Highly efficient photocatalytic dehalogenation of organic halides on TiO2 loaded with bimetallic Pd-Pt alloy nanoparticles

UV irradiation of TiO(2) loaded with bimetallic Pd-Pt alloy particles promotes highly efficient dehalogenation of organic halides with alcohol as a hydrogen source.

Production of electricity and hydrogen by photocatalytic degradation of organic wastes in a photoelectrochemical cell: the concept of the Photofuelcell: a review of a re-emerging research field

The present review aims to give to a researcher who has no experience with Photofuelcells all necessary basic knowledge to join the field without much trouble and to give to an experienced researcher a handy manual of reference. The author has dealt with the principal matters related with the design of a photoelectrochemical cell and the factors that affect efficient production of electricity by photocatalytic degradation of (principally) organic and (secondarily) inorganic waste materials. A large portion of the paper is devoted to the review of materials used for making a photoanode since most of the accomplished research is on this exact matter. The paper also briefly reviews the materials used to make the rest of the components of the cell as well as the models of cell efficiency and photodegradation procedures during cell operation.