Investigation of photoelectrocatalytic degradation mechanism of methylene blue by a-Fe_(2)O_(3) nanorods array

Efficiently and thoroughly degrading organic dyes in wastewater is of great importance and challenge.Herein,vertically oriented mesoporous a-Fe_(2)O_(3)nanorods array(a-Fe_(2)O_(3)-NA)is directly grown on fluorine-doped tin oxide(FTO)glass and employed as the photoanode for photoelectrocatalytic degradation of methylene blue simulated dye wastewater.The Ovsites on the a-Fe_(2)O_(3)-NA surface are the active sites for methylene blue(MB)adsorption.Electrons transfer from the adsorbed MB to Fe-O is detected.Compared with electrocatalytic and photocatalytic degradation processes,the photoelectrocatalytic(PEC)process exhibited the best degrading performance and the largest kinetic constant.Hydroxyl,superoxide free radicals,and photo-generated holes play a jointly leading role in the PEC degradation.A possible degrading pathway is suggested by liquid chromatography-mass spectroscopy analysis.This work demonstrates that photoelectrocatalysis by a-Fe_(2)O_(3)-NA has a remarkable superiority over photocatalysis and electrocatalysis in MB degradation.The in-depth investigation of photoelectrocatalytic degradation mechanism in this study is meaningful for organic wastewater treatment.

Photoelectrocatalytic reduction of CO_2 into formic acid using WO_(3-x)/TiO_2 film as novel photoanode

A novel WO3-x/TiO2 film as photoanode was synthesized for photoelectrocatalytic（PEC） reduction of CO2 into formic acid（HCOOH）. The films prepared by doctor blade method were characterized with X-ray diffractometer（XRD）, scanning electron microscope（SEM） and transmission electron microscope（TEM）. The existence of oxygen vacancies in the WO3-x was confirmed with an X-ray photoelectron spectroscopy（XPS）, and the accurate oxygen index was determined by a modified potentiometric titrimetry method. After 3h of photoelectrocatalytic reduction, the formic acid yield of the WO3-x/TiO2 film is 872 nmol/cm^2, which is 1.83 times that of the WO3/TiO2 film. The results of PEC performance demonstrate that the introduction of WO3-x nanoparticles can improve the charge transfer performance so as to enhance the performance of PEC reduction of CO2 into formic acid.

Degradation of 2,4-dichlorophenol with a novel TiO_2/Ti-Fe-graphite felt photoelectrocatalytic oxidation process

Degradation of 2,4-dichlorophenol （2,4-DCP） was studied in a novel three-electrode photoelectrocatalytic （PEC） integrative oxidation process, and the factors influencing the degradation rate, such as applied current, flow speed of O2, pH, adscititious voltage and initial 2,4-DCP concentration were investigated and optimized. H2O2 was produced nearby cathode and Fe^2＋ continuously generated from Fe anode in solution when current and O2 were applied, so, main reactions, H2O2-assisted TiO2 PEC oxidation and E-Fenton reaction, occurred during degradation of 2,4-DCP in this integrative system. The degradation ratio of 2,4-DCP was 93% in this integrative oxidation process, while it was only 31% in E-Fenton process and 46% in H2O2-assisted TiO2 PEC process. So, it revealed that the degradation of 2,4-DCP was improved greatly by photoelectrical cooperation effect. By the investigation of pH, it showed that this integrative process could work well in a wide pH range from pH 3 to pH 9.

BiVO4/TiO2(N2) Nanotubes Heterojunction Photoanode for Highly Efficient Photoelectrocatalytic Applications

We report the development of a novel visible response BiVO_4/TiO_2(N_2) nanotubes photoanode for photoelectrocatalytic applications. The nitrogen-treated TiO_2 nanotube shows a high carrier concentration rate, thus resulting in a high efficient charge transportation and low electron–hole recombination in the TiO_2–BiVO_4. Therefore, the BiVO_4/TiO_2(N_2) NTs photoanode enabled with a significantly enhanced photocurrent of 2.73 mA cm^(-2)(at 1 V vs. Ag/Ag Cl) and a degradation efficiency in the oxidation of dyes under visible light. Field emission scanning electron microscopy, X-ray diffractometry, energy-dispersive X-ray spectrometer, and UV–Vis absorption spectrum were conducted to characterize the photoanode and demonstrated the presence of both metal oxides as a junction composite.

Kinetics of photoelectrocatalytic degradation of humic acid using B_2O_3·TiO_2/Ti photoelectrode

An innovative photoelectrode, B 2O 3·TiO 2/Ti electrode, was prepared by galvanostaticanodisation. The morphology and crystalline texture of the B 2O 3·TiO 2 film on electrode were examined by atomic force microscopy(AFM) and X-ray diffraction respectively. The examination results indicated that the anatase was the dominant component. The kinetics of photoelectrocatalytic(PEC) degradation of humic acid(HA) was investigated; the results demonstrated that effects from strongness to weakness on the photoelectrocatalytic degraded rate of humic acid: power of UV-lamp, area of TiO 2 film, bias, original concentration of humic acid solution. The optimum conditions were power of UV-lamp 125 W, area of TiO 2 film 42.0 cm 2, bias 1.4 V, original concentration of humic acid solution 5 mg/L in this PEC reaction system.

Efficient photoelectrocatalytic CO_2 reduction by cobalt complexes at silicon electrode

Two homogeneous photoelectrocatalytic systems composed of simple polypyridyl Co complexes[Co(tpy)2](PF6)2and[Co(bpy)3](PF6)2as electrocatalysts and a Si wafer as the photoelectrode were used for combined photoelectrochemical reduction of CO2to CO.A high photocurrent density of1.4mA/cm2was observed for the system with the[Co(tpy)2](PF6)2catalyst and a photovoltage of400mV was generated.Faradaic efficiencies of CO were optimized to83%and94%for the[Co(tpy)2](PF6)2and[Co(bpy)3](PF6)2complexes,respectively,in acetonitrile solution with10%methanol(volume fraction,same below)as a protic additive.Addition of2%water volume fraction induced a large amount of non‐specific H2evolution by the Si photoelectrode.

Photoelectrocatalytic degradation of Rose Bengal

An innovative photoelectrode, TiO 2/Ti mesh electrode, was prepared by galvanostaticanodisation. The morphology and the crystalline texture of the TiO 2 film on mesh electrode were examined by scanning electronic microscopy and Raman spectroscopy respectively. The examination results indicated that the structure and properties of the film depended on anodisation rate, and the anatase was the dominant component under the controlled experimental conditions. Degradation of Rose Bengal(RB) in photocatalytic(PC) and photoelectrocatalytic(PEC) reaction was investigated, the results demonstrated that electric biasing could improve the efficiency of photocatalytic reaction. The measurement results of TOC in photoelectrocatalytic degradation showed that the mineralisation of RB was complete relatively. The comparison between the degradation efficiency of RB in PEC process and that in aqueous TiO 2 dispersion was conducted. The results showed that the apparent first order rate constant of RB degradation in PEC process was larger than that in aqueous dispersion with 0 1%—0 3% TiO 2 powder, but was smaller than that in aqueous dispersion with 1 0% TiO 2

α-Fe_(2)O_(3)/Cu_(2)O composites as catalysts for photoelectrocatalytic degradation of benzotriazoles

Given the difficulties of degrading benzotriazole(BTA),this study used a one-pot hydrothermal method to prepareα-Fe_(2)O_(3)/Cu_(2)O(FC)composites for photoelectrocatalytic(PEC)degradation of BTA.The characterization of FC structure showed that Cu_(2)O in cubic crystals was loaded with circular sheets of Fe_(2)O_(3).Owing to this structure,FC showed efficient PEC degradation of BTA when exposed to ultraviolet light.The experimental results demonstrated that FC efficiently degraded BTA.When the PEC degradation continued for 60 min,100%degradation of BTA was achieved because FC enhanced the photoelectron-hole separation and the separation and transfer of articulated carriers.High per-formance liquid chromatography-mass spectrometry showed that intermediates formed during the PEC degradation of BTA.Finally,various pathways for degradation of BTA were postulated.This FC-based PEC system provides a harmless and effective method for degradation of BTA.

Increase the Degradation Efficiency of Organic Pollutants with a Radical Scavenger (Cl) in a Novel Photoelectrocatalytic Reactor

Photoelectrocatalytic degradation performance of quinoline in saline water was investigated using a new-designed continuous flow three-dimensional electrode-packed bed photocatalytic reactor. It is interesting to find that chloride ion has an obvious enhancement effect rather than a scavenging effect on the photoelectrocatalytic degradation of quinoline, and create a kinetic synergetic effect in the photoelectrocatalytic reactor.

Ti^(3+) self-doped TiO_2 photoelectrodes for photoelectrochemical water splitting and photoelectrocatalytic pollutant degradation

To improve the harvesting of visible light and reduce the recombination of photogenerated electrons and holes, Ti3+ self-doped TiO2 nanoparticles were synthesized and assembled into photoanodes with high visible light photoelectrochemical properties. X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectra, electron resonance spectroscopy and energy dispersive X-ray spectra were used to characterize the structure, crystallinity, morphology and other properties of the obtained nanoparticles. UV-visible diffuse reflectance spectra showed that the Ti3+ self-doped TiO2 nanoparticles had a strong absorption between 400 and 800 nm. Moreover, when hydrothermal treatment time was prolonged to 22 h, the heterogeneous junction was formed between the anatase and rutile TiO2, where the anatase particles exposed highly active {001} facets. Under visible light irradiation, the Ti3+ self-doped TiO2 electrode exhibited an excellent photoelectrocatalytic degradation of rhodamine B (RhB) and water splitting performance. Intriguingly, by selecting an appropriate hydrothermal time, the high photoconversion efficiency of 1.16% was achieved. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.

Research Progress on Photocatalytic/Photoelectrocatalytic Oxidation of Nitrogen Oxides

The emission of nitrogen oxides(NO_(x))increases year by year,causing serious problems to our livelihoods.The photocatalytic oxidation of NO_(x)has attracted more attention recently because of its effi cient removal of NO_(x),especially for low concentra-tions of NO_(x).In this review,the mechanism of the photocatalytic oxidation of NO_(x)is described.Then,the recent progress on the development of photocatalysts is reviewed according to the categories of inorganic semiconductors,bismuth-based compounds,nitrogen carbide polymer,and metal organic frameworks(MOFs).In addition,the photoelectrocatalytic oxida-tion of NO_(x),a method involving the application of an external voltage on the photocatalytic system to further increase the removal effi ciency of NO_(x),and its progress are summarized.Finally,we outline the remaining challenges and provide our perspectives on the future directions for the photocatalytic oxidation of NO_(x).

Kinetics of photoelectrocatalytic degradation of endocrine disrupting chemicals using sulfur-doped TiO_2 /Ti photoelectrodes

In this study,sulfur-doped TiO2 /Ti photoelectrodes were prepared by anodization. The morphology, crystalline structure,composition of sulfur-doped TiO2 /Ti film and light absorption property were examined by SEM,XRD,XRF,XPS and UV/VIS respectively. Dimethyl phthalate( DMP) ,one kind of environmental disrupting chemicals( EDCs) ,was degraded by the optimized photoelectrodes. Power of xenon light,initial concentration of DMP,photoelectrocatalytic( PEC) area of photoelectrode and bias were investigated in the study on kinetics of PEC degradation of DMP. Hence,this study concluded that the optimum conditions were power of xenon light 150 W,initial concentration of DMP 1 mg/L,PEC area of sulfur-doped TiO2 /Ti photoelectrode 10 cm2,bias 1. 3 V in the PEC reaction system.

Photoelectrocatalytic Oxidation of Ethinylestradiol on a Ti/TiO₂Electrode: Degradation Efficiency and Search for By-Products

The degradation of ethinylestradiol (EE, an orally bio-active estrogen) in an aqueous-methanolic solution using a Ti/TiO2 thin-film electrode and UV radiation (a photoelectrocatalytic system) was evaluated. Hence, HPLC/UV analysis shows that EE (at 0.34 mmol) is totally consumed after 30 minutes of exposure to the photoelectrocatalytic system in the presence of Na2SO4 (0.1 mol·L-1) and with an applied bias potential of +1.0 V versus the Ag/AgCl reference electrode. Moreover, monitoring by direct infusion electrospray ionization mass spectrometry (ESI-MS) and SPME-GC/ MS (solid phase microextraction coupled with gas chromatography-mass spectrometry) reveals that apparently no degradation products are formed under these conditions. Hence, this study demonstrates that the photoelectrocatalytic system can be efficiently used to promote the complete degradation (and likely mineralization) of this hormone under these conditions.

Enhanced photoelectrocatalytic decomplexation of Ni-EDTA and simultaneous recovery of metallic nickel via TiO_(2)/Ni-Sb-SnO_(2) bifunctional photoanode and activated carbon fiber cathode

In order to enhance Ni-EDTA decomplexation and Ni recovery via photoelectrocatalytic (PEC)process,TiO_(2)/Ni-Sb-SnO_(2)bifunctional electrode was fabricated as the photoanode and activated carbon fiber (ACF) was introduced as the cathode.At a cell voltage of 3.5 V and initial solution pH of 6.3,the TiO_(2)/Ni-Sb-SnO_(2)bifunctional photoanode exhibited a synergetic effect on the decomplexation of Ni-EDTA with the pseudo-first-order rate constant of 0.01068 min^(-1)with 180 min by using stainless steel (SS) cathode,which was 1.5 and 2.4times higher than that of TiO_(2)photoanode and Ni-Sb-SnO_(2)anode,respectively.Moreover,both the efficiencies of Ni-EDTA decomplexation and Ni recovery were improved to 98%from 86%and 73%from 41%after replacing SS cathode with ACF cathode,respectively.Influencing factors on Ni-EDTA decomplexation and Ni recovery were investigated and the efficiencies were favored at acidic condition,higher cell voltage and lower initial Ni-EDTA concentration.Ni-EDTA was mainly decomposed via·OH radicals which generated via the interaction of O_(3),H_(2)O_(2),and UV irradiation in the contrasted PEC system.Then,the liberated Ni^(2+)ions which liberated from Ni-EDTA decomplexation were eventually reduced to metallic Ni on the ACF cathode surface.Finally,the stability of the constructed PEC system on Ni-EDTA decomplexation and Ni recovery was exhibited.

High-entropy layered oxides nanosheets for highly efficient photoelectrocatalytic reduction of CO_(2)and application research

High-entropy oxides receive significant attention owing to their“four effects”.However,they still suffer from harsh construction conditions such as high temperature and high pressure and present a block-like structure.Herein,in this work,Ni-Mn-Cu-Co-Fe-Al high-entropy layered oxides(HELOs)with a layered nanosheet structure were constructed by a simple pathway of topological transformation under relatively low temperature(300℃)with six-membered Ni-Mn-Cu-Co-Fe-Al layered double hydroxides(LDHs)precursors,which exhibited an outstanding activity and excellent selectivity for CO_(2)photoelectroreduction(obtaining the highest carbon monoxide yield of 909.55μmol·g^(−1)·h^(−1)under−0.8 V vs.reversible hydrogen electrode(RHE),which is almost twice that of pure electrocatalysis).In addition,the charging voltage of a photo-assisted Zn-CO_(2)battery with HELOs as electrode was reduced from 2.62 to 2.40 V;the discharging voltage of the battery was increased from 0.51 to 0.59 V with the assistance of illumination.The improvement of round-trip efficiency of the battery indicates that light played a positive role in both the charging and discharging processes.This study not only lays an important foundation for the development of high-entropy oxides but also expands their application in the field of photoelectrochemistry.

Upcycling plastic wastes into value-added products via electrocatalysis and photoelectrocatalysis

Plastic,renowned for its versatility,durability,and cost-effectiveness,is indispensable in modern society.Nevertheless,the annual production of nearly 400 million tons of plastic,coupled with a recycling rate of only 9%,has led to a monumental environmental crisis.Plastic recycling has emerged as a vital response to this crisis,offering sustainable solutions to mitigate its environmental impact.Among these recycling efforts,plastic upcycling has garnered attention,which elevates discarded plastics into higher-value products.Here,electrocatalytic and photoelectrocatalytic treatments stand at the forefront of advanced plastic upcycling.Electrocatalytic or photoelectrocatalytic treatments involve chemical reactions that facilitate electron transfer through the electrode/electrolyte interface,driven by electrical or solar energy,respectively.These methods enable precise control of chemical reactions,harnessing potential,current density,or light to yield valuable chemical products.This review explores recent progress in plastic upcycling through electrocatalytic and photoelectrocatalytic pathways,offering promising solutions to the plastic waste crisis and advancing sustainability in the plastics industry.

Approaches to Improving Selectivity During Photoelectrochemical Transformation of Small Molecules

Photoelectrochemical (PEC) small-molecule oxidation can selectively transform substrates into high-value-added fine chemicals and increase the rate of cathode hydrogen evolution. Nevertheless, achieving high-selectivity PEC oxidation of small molecules to produce specific products is a very challenging task. In general, selectivity can be improved by changing the surface catalyticsites of the photoanode and modulating the interfacial environments of the reactions. Herein, recent advances in approaches to improving selective PEC oxidation of small molecules are introduced. We first briefly discuss the basic concept and fundamentals of small-molecule PEC oxidation. The reported approaches to improving the performance of selective PEC oxidation of small molecules are highlighted from two aspects: (1) changing the surface properties of photoanodes by selecting suitable materials or modifying the photoanodes and (2) mediating the oxidation reactions using redox mediators. The PEC oxidation mechanism of these studies is emphasized. We also discuss the challenges in this research direction and offer a perspective on the further development of selective PEC-based small-molecule transformation.

Photoelectrochemical performance of birnessite films and photoelectrocatalytic activity toward oxidation of phenol

Birnessite films on fluorine-doped tin oxide（FTO） coated glass were prepared by cathodic reduction of aqueous KMnO4. The deposited birnessite films were characterized with X-ray diffraction, Raman spectroscopy, scanning electron microscopy and atomic force microscopy.The photoelectrochemical activity of birnessite films was investigated and a remarkable photocurrent in response to visible light was observed in the presence of phenol, resulting from localized manganese d–d transitions. Based on this result, the photoelectrocatalytic oxidation of phenol was investigated. Compared with phenol degradation by the electrochemical oxidation process or photocatalysis separately, a synergetic photoelectrocatalytic degradation effect was observed in the presence of the birnessite film coated FTO electrode.Photoelectrocatalytic degradation ratios were influenced by film thickness and initial phenol concentrations. Phenol degradation with the thinnest birnessite film and initial phenol concentration of 10 mg/L showed the highest efficiency of 91.4% after 8 hr. Meanwhile, the kinetics of phenol removal was fit well by the pseudofirst-order kinetic model.

Photoelectrocatalytic reduction of CO_2 to methanol over a photosystem Ⅱ-enhanced Cu foam/Si-nanowire system

A solar-light double illumination photoelectrocatalytic cell（SLDIPEC） was fabricated for autonomous CO2 reduction and O2 evolution with the aid of photosystem II（PS-II, an efficient light-driven water-oxidized enzyme from nature） and utilized in a photoanode solution. The proposed SLPEC system was composed of Cu foam as the photoanode and p-Si nanowires（Si-NW） as the photocathode. Under solar irradiation, it exhibited a super-photoelectrocatalytic performance for CO2 conversion to methanol, with a high evolution rate（41.94 mmol/hr）, owing to fast electron transfer from PS-II to Cu foam.Electrons were subsequently trapped by Si-NW through an external circuit via bias voltage（0.5 V）, and a suitable conduction band potential of Si（-0.6 e V） allowed CO2 to be easily reduced to CH3 OH at the photocathode. The constructed Z-scheme between Cu foam and Si-NW can allow the SLDIPEC system to reduce CO2（8.03 mmol/hr） in the absence of bias voltage. This approach makes full use of the energy band mismatch of the photoanode and photocathode to design a highly efficient device for solving environmental issues and producing clean energy.

Construction of high-efficient visible photoelectrocatalytic system for carbamazepine degradation:Kinetics,degradation pathway and mechanism

This study aimed to construct a photoelectrocatalytic(PEC)reaction system based on the self-made reduced TiO_(2) NTAs(r-TNAs)photoanode and activated carbon/Polytetrafluoroethylene(AC/PTFE)cathode.It would be observed clearly that the degradation rate constant of carbamazepine(CBZ)over r-TNAs(photoanode)-AC/PTFE(cathode)PEC system(0.04961 min^(-1))was even higher than that of r-TNAs(photoanode)-Pt(cathode)PEC system(0.04602 min^(-1))with the assistance of visible light irradiation and+0.4 V external potential.Besides,in order to obtain optimized conditions,the influence of key parameters such as pH value,electric current density and electrolyte concentration were studied.Most impo rtantly,photoelectrochemical(PECH)properties,reactive oxide species contribution.OH formation rate and CBZ degradation pathway were determined.The results illustrated that the excellent PEC degradation performance depended on the excellent photocatalytic property of r-TNAs photoanode and electron transfer prope rty of photoelectrodes in r-TNAs(photoanode)-AC/PTFE(cathode)PEC system.Therefo re,the study demonstrated that the r-TNAs(photoanode)-AC/PTFE(cathode)PEC system could be expected to replace metal-catalyzed cathodes depending on its excellent PEC performance activity and low cost as well as the reaction system possessed objective and practical application prospect.