Copper-doped TiO₂ photocatalyst for advanced oxidation processes: reactive oxygen species generation mechanisms

Abstract

Copper-doped anatase TiO₂ (Cu/TiO₂) has attracted significant attention in various sustainable chemical processes, including water splitting, carbon monoxide oxidation, carbon dioxide reduction, chemical synthesis, and advanced oxidation processes for water treatment. Reactive oxygen species (ROS) are involved in these processes, but a mechanistic understanding of ROS generation on Cu/TiO₂ surfaces has not been established. Combining experimental investigation and computational simulation, this work provides unequivocal evidence for superoxide radical anion (O₂^•-) formation via reduction of the adsorbed oxygen by Cu⁺ and hydroxyl radical (^•OH) production by oxidation of lattice oxygen within the bridging Cu-O-Ti structure on Cu/TiO₂ surfaces. Under visible light irradiation, the ROS generation rates of Cu/TiO₂ are 7.2 times higher for O₂^•- and 11.2 times higher for ^•OH than those of undoped TiO₂. The superior performance of Cu/TiO₂ has been demonstrated through its organic dye degradation, bactericidal activity, and biofilm disruption, indicating its wide applicability in water treatment and disinfection. The results and the methodologies will benefit the wide field of heterogeneous redox chemistry.

Keywords

Heterogeneous redox chemistry / sustainable chemistry / organic dye / biofilm / disinfectant / antimicrobial effect

References

[1] Fujishima A.Electrochemical photolysis of water at a semiconductor electrode.Nature1972;238:37-8

[2] Zhang H,Lv X,Chang H.Energy-efficient photodegradation of azo dyes with TiO₂ nanoparticles based on photoisomerization and alternate UV-visible light.Environ Sci Technol2010;44:1107-11

[3] Hashimoto K,Sakata T.Temperature-independent electron-transfer: Rhodamine B/oxide semiconductor dye-sensitization system.J Phys Chem1988;92:4272-4

[4] Basavarajappa PS,Ganganagappa N,Raghu AV.Recent progress in metal-doped TiO₂, non-metal doped/codoped TiO₂ and TiO₂ nanostructured hybrids for enhanced photocatalysis.Int J Hydrogen Energy2020;45:7764-78

[5] Paola AD,Marcì G,Palmisano L.Transition metal doped TiO₂: physical properties and photocatalytic behaviour.Int J Photoenergy2001;3:171-6

[6] Wang B,Mao SS.Black TiO₂ for solar hydrogen conversion.J Materiomics2017;3:96-111

[7] Zhang K.Surface localization of defects in black TiO₂: enhancing photoactivity or reactivity.J Phys Chem Lett2017;8:199-207

[8] Erdural B,Karakas G.Photocatalytic antibacterial activity of TiO₂–SiO₂ thin films: the effect of composition on cell adhesion and antibacterial activity.J Photochem Photobiol A Chem2014;283:29-37

[9] Ya J,Hu F,E L.Preparation and activity evaluation of TiO₂/Cu-TiO₂ composite catalysts.J Sol Gel Sci Technol2015;73:322-31

[10] Chen F,Hidaka H.Highly selective deethylation of rhodamine B: adsorption and photooxidation pathways of the dye on the TiO₂/SiO₂ composite photocatalyst.Int J Photoenergy2003;5:209-17

[11] Liu Z,Zhang Q,Sun H.TiO₂-supported single-atom catalysts: synthesis, structure, and application.Chem Res Chin Univ2022;38:1123-38

[12] Janisch R,Spaldin NA.Transition metal-doped TiO₂ and ZnO - present status of the field.J Phys Condens Matter2005;17:R657-89

[13] Song H,Lou Z,Zhu L.Effective formation of oxygen vacancies in black TiO₂ nanostructures with efficient solar-driven water splitting.ACS Sustainable Chem Eng2017;5:8982-7

[14] Hejazi S,Mazare A.Single-atom-based catalysts for photocatalytic water splitting on TiO₂ nanostructures.Catalysts2022;12:905

[15] Tomboc GM,Jung S,Lee K.Modulating the local coordination environment of single-atom catalysts for enhanced catalytic performance in hydrogen/oxygen evolution reaction.Small2022;18:e2105680

[16] Lee BH,Kim M.Reversible and cooperative photoactivation of single-atom Cu/TiO₂ photocatalysts.Nat Mater2019;18:620-6

[17] Wang H,Sun X.High quantum efficiency of hydrogen production from methanol aqueous solution with PtCu-TiO₂ photocatalysts.Nat Mater2023;22:619-26

[18] Fang Y,Zhang H.Dual activation of molecular oxygen and surface lattice oxygen in single atom Cu₁/TiO₂ catalyst for CO oxidation.Angew Chem Int Ed Engl2022;61:e202212273

[19] Iyemperumal SK,Bauer J.Quantifying support interactions and reactivity trends of single metal atom catalysts over TiO₂.J Phys Chem C2018;122:25274-89

[20] Qi R,Han Z.High-throughput screening of stable single-atom catalysts in CO₂ reduction reactions.ACS Catal2022;12:8269-78

[21] De S,Ramirez A.Advances in the design of heterogeneous catalysts and thermocatalytic processes for CO₂ utilization.ACS Catal2020;10:14147-85

[22] Hu G,Jiang D.First principles insight into H₂ activation and hydride species on TiO₂ surfaces.J Phys Chem C2018;122:20323-8

[23] Liu P,Qin R.Photochemical route for synthesizing atomically dispersed palladium catalysts.Science2016;352:797-801

[24] Hu J,Janik MJ.Hydrogen activation and spillover on anatase TiO₂-supported Ag single-atom catalysts.J Phys Chem C2022;126:7482-91

[25] Li D,Miao Y.Accelerating electron-transfer dynamics by TiO₂-immobilized reversible single-atom copper for enhanced artificial photosynthesis of urea.Adv Mater2022;34:e2207793

[26] Guo Y,Zeng B.Photo-thermo semi-hydrogenation of acetylene on Pd₁/TiO₂ single-atom catalyst.Nat Commun2022;13:2648 PMCID:PMC9098498

[27] Kim SS,Hong SC.The effect of the morphological characteristics of TiO₂ supports on the reverse water–gas shift reaction over Pt/TiO₂ catalysts.Appl Catal B Environ2012;119-20:100-8

[28] Chen L,Hoffman AS.Unlocking the catalytic potential of TiO₂-supported Pt single atoms for the reverse water-gas shift reaction by altering their chemical environment.JACS Au2021;1:977-86 PMCID:PMC8395703

[29] Nelson NC,Meira D,Szanyi J.In situ dispersion of palladium on TiO₂ during reverse water–gas shift reaction: formation of atomically dispersed palladium.Angew Chem Int Ed Engl2020;132:17810-6

[30] Astruc D,Aranzaes JR.Nanoparticles as recyclable catalysts: the frontier between homogeneous and heterogeneous catalysis.Angew Chem Int Ed Engl2005;44:7852-72

[31] Byrne C,Hermosilla D.Effect of Cu doping on the anatase-to-rutile phase transition in TiO₂ photocatalysts: theory and experiments.Appl Catal B Environ2019;246:266-76

[32] Cheng C,Long R.Water splitting with a single-atom Cu/TiO₂ photocatalyst: atomistic origin of high efficiency and proposed enhancement by spin selection.JACS Au2021;1:550-9 PMCID:PMC8395698

[33] Cao Z,Zuo YY.An optical method for quantitatively determining the surface free energy of micro- and nanoparticles.Anal Chem2019;91:12819-26

[34] Chen X,Yu PY.Increasing solar absorption for photocatalysis with black hydrogenated titanium dioxide nanocrystals.Science2011;331:746-50

[35] Kim A,Haye B,Sassoye C.Mesoporous TiO₂ support materials for Ru-based CO₂ methanation catalysts.ACS Appl Nano Mater2019;2:3220-30

[36] Martell SA,Dasog M.The influence of hydrofluoric acid etching processes on the photocatalytic hydrogen evolution reaction using mesoporous silicon nanoparticles.Faraday Discuss2020;222:176-89

[37] Kirshenbaum MJ,Dasog M.Electrochemical water oxidation in acidic solution using titanium diboride (TiB₂) catalyst.ChemCatChem2019;11:3877-81

[38] Gelderman K,Donne SW.Flat-band potential of a semiconductor: using the Mott–Schottky equation.J Chem Educ2007;84:685

[39] Balu S,Chen SW.Rational synthesis of Bi_xFe_1-xVO₄ heterostructures impregnated sulfur-doped g-C₃N₄: a visible-light-driven type-II heterojunction photo(electro)catalyst for efficient photodegradation of roxarsone and photoelectrochemical OER reactions.Appl Catal B Environ2022;304:120852

[40] Kautek W.Photoelectrochemical reactions and formation of inversion layers at n-type MoS₂-, MoSe₂-, and WSe₂-electrodes in aprotic solvents.Ber Bunsenges Phys Chem1980;84:645-53

[41] Feenstra RM.Tunneling spectroscopy of the GaAs(110) surface.J Vac Sci Technol B1987;5:923-9

[42] Seger B,Pedersen T.Silicon protected with atomic layer deposited TiO₂: conducting versus tunnelling through TiO₂.J Mater Chem A2013;1:15089

[43] Yin M,Kou J.Mechanism investigation of visible light-induced degradation in a heterogeneous TiO₂/eosin Y/rhodamine B system.Environ Sci Technol2009;43:8361-6

[44] Jo WK,Tonda S.Hierarchical flower-like NiAl-layered double hydroxide microspheres encapsulated with black Cu-doped TiO₂ nanoparticles: highly efficient visible-light-driven composite photocatalysts for environmental remediation.J Hazard Mater2018;357:19-29

[45] Zhang D,Song L,Mo Y.Role of oxygen active species in the photocatalytic degradation of phenol using polymer sensitized TiO₂ under visible light irradiation.J Hazard Mater2009;163:843-7

[46] Yuan G,Li Y.A modified hestenes and stiefel conjugate gradient algorithm for large-scale nonsmooth minimizations and nonlinear equations.J Optim Theory Appl2016;168:129-52

[47] Mato J.Accuracy of the PM6 and PM7 methods on bare and thiolate-protected gold nanoclusters.J Phys Chem A2020;124:2601-15

[48] Baker J.An algorithm for the location of transition states.J Comput Chem1986;7:385-95

[49] Li G,Chen L,Gray KA.Role of surface/interfacial Cu²⁺ sites in the photocatalytic activity of coupled CuO−TiO₂ nanocomposites.J Phys Chem C2008;112:19040-4

[50] Moniz SJA.Charge transfer and photocatalytic activity in CuO/TiO₂ nanoparticle heterojunctions synthesised through a rapid, one-pot, microwave solvothermal route.ChemCatChem2015;7:1659-67

[51] Bhattacharyya K,Rane V,Tyagi AK.Selective CO₂ photoreduction with Cu-doped TiO₂ photocatalyst: delineating the crucial role of Cu-oxidation state and oxygen vacancies.J Phys Chem C2021;125:1793-810

[52] Setvín M,Scheiber P.Reaction of O₂ with subsurface oxygen vacancies on TiO₂ anatase (101).Science2013;341:988-91

[53] Bredow T.Electronic structure of an isolated oxygen vacancy at the TiO₂(110) surface.Chem Phys Lett2002;355:417-23

[54] Pacchioni G.Oxygen vacancy: the invisible agent on oxide surfaces.Chemphyschem2003;4:1041-7

[55] You M,Sung Y.Synthesis of Cu-doped TiO₂ nanorods with various aspect ratios and dopant concentrations.Cryst Growth Des2010;10:983-7

[56] Kang L,Bing Q.Adsorption and activation of molecular oxygen over atomic copper(I/II) site on ceria.Nat Commun2020;11:4008 PMCID:PMC7419315

[57] Colón G,Hidalgo M.Cu-doped TiO₂ systems with improved photocatalytic activity.Appl Catal B Environ2006;67:41-51

[58] Takanabe K.Photocatalytic water splitting: quantitative approaches toward photocatalyst by design.ACS Catal2017;7:8006-22

[59] Choudhury B,Choudhury A.Defect generation, d-d transition, and band gap reduction in Cu-doped TiO₂ nanoparticles.Int Nano Lett2013;3:52

[60] Rengifo-Herrera JA.Why five decades of massive research on heterogeneous photocatalysis, especially on TiO₂, has not yet driven to water disinfection and detoxification applications? Critical review of drawbacks and challenges.Chem Eng J2023;477:146875

[61] Kandoth N,Gupta S.Multimodal biofilm inactivation using a photocatalytic bismuth perovskite-TiO₂-Ru(II)polypyridyl-based multisite heterojunction.ACS Nano2023;17:10393-406

[62] Wu T,Zhao J,Serpone N.TiO₂-assisted photodegradation of dyes. 9. Photooxidation of a squarylium cyanine dye in aqueous dispersions under visible light irradiation.Environ Sci Technol1999;33:1379-87

[63] Amorelli A,Rowlands CC.Electron paramagnetic resonance study of the effect of temperature upon copper-impregnated titanium dioxide powders.J Chem Soc Faraday Trans 11989;85:4111

[64] Shi X,Huang L.Copper catalysts in semihydrogenation of acetylene: from single atoms to nanoparticles.ACS Catal2020;10:3495-504

[65] Zhang Y,Wang H.Single-atom Cu anchored catalysts for photocatalytic renewable H₂ production with a quantum efficiency of 56.Nat Commun2022;13:58 PMCID:PMC8748625

[66] Zhao Y,Shi R.Tuning oxygen vacancies in ultrathin TiO₂ nanosheets to boost photocatalytic nitrogen fixation up to 700 nm.Adv Mater2019;31:e1806482

[67] Zhao Y,Waterhouse GIN.Layered-double-hydroxide nanosheets as efficient visible-light-driven photocatalysts for dinitrogen fixation.Adv Mater2017;29:1703828

[68] Dohshi S,Okuda S.Effect of γ-ray Irradiation on the Wettability of TiO₂ single crystals.Top Catal2005;35:327-30

[69] Pan C,Liu G.CuO/TiO₂ nanobelt with oxygen vacancies for visible-light-driven photocatalytic bacterial inactivation.ACS Appl Nano Mater2022;5:10980-90

[70] Nakamura R.Molecular mechanism of water oxidation reaction at photo-irradiated TiO₂ and related metal oxide surfaces.Solid State Phenom2010;162:1-27

[71] Nosaka Y.Understanding hydroxyl radical (^•OH) generation processes in photocatalysis.ACS Energy Lett2016;1:356-9

[72] Kim B,Ohta T.Nucleophilic reactivity of a copper(II)-hydroperoxo complex.Commun Chem2019;2:187

[73] Nosaka Y.Generation and detection of reactive oxygen species in photocatalysis.Chem Rev2017;117:11302-36

[74] Nosaka Y,Nosaka AY.Singlet oxygen formation in photocatalytic TiO₂ aqueous suspension.Phys Chem Chem Phys2004;6:2917

[75] Jakimińska A,Macyk W.Photocatalytic transformation of Rhodamine B to Rhodamine-110 - the mechanism revisited.J Photochem Photobiol A Chem2022;433:114176

[76] Wu T,Zhao J,Serpone N.Photoassisted degradation of dye pollutants. V. Self-photosensitized oxidative transformation of Rhodamine B under visible light irradiation in aqueous TiO₂ dispersions.J Phys Chem B1998;102:5845-51

[77] Skjolding LM,Dyhr KS.Assessing the aquatic toxicity and environmental safety of tracer compounds Rhodamine B and Rhodamine WT.Water Res2021;197:117109

[78] Jańczyk A,Stochel G.Singlet oxygen photogeneration at surface modified titanium dioxide.J Am Chem Soc2006;128:15574-5

[79] Curry DE,Carrier AJ.Surface interaction of doxorubicin with anatase determines its photodegradation mechanism: insights into removal of waterborne pharmaceuticals by TiO₂ nanoparticles.Environ Sci Nano2018;5:1027-35

[80] Loeb SK,Brame JA.The technology horizon for photocatalytic water treatment: sunrise or sunset?.Environ Sci Technol2019;53:2937-47