TiO2 Surface Research Articles

Novel D–π–A dye as a co-sensitizer of indoline and benzothiadiazole dyes to enhance photovoltaic performance of dye-sensitized solar cells

A novel D–π–A type of dye (BIM33) comprising diphenylamine as electron donor, diphenylacridine as a π-bridge and cyanoacrylic acid as an anchoring unit has been synthesized and used as sensitizer and co-sensitizer in dye-sensitized solar cells (DSSCs). The DSSC based on BIM33 achieved a power conversion efficiency (PCE) of 3.19 % under one sun (AM 1.5G). To improve the photovoltaic performance of the DSSCs, this orange dye was also co-sensitized with red benzothiadiazole (C1) and purple indoline (D205) organic dyes. The DSSCs based on co-sensitizers BIM33/D205 and BIM33/C1 showed superior PCEs of 6.57 % (JSC = 13.69 mA cm−2, VOC = 0.766 V, and FF = 0.63) and 6.82 % (JSC = 14.47 mA cm−2, VOC = 0.722 V, and FF = 0.65), respectively, exhibiting significant improvements of 28 % and 36 % compared to the DSSCs based on D205 and C1, respectively. The high photovoltaic performance of the co-sensitized DSSCs may be explained by the broader visible light absorption and a denser packing of the dyes on the TiO2 surface.

Assemble of porous heterostructure thin film through CuS passivation for efficient electron transport in dye-sensitized solar cells

Three different modified solar cells have been passivated with copper sulfide (CuS) on a TiO2 electrode and manganese sulfide (γ‐MnS) hexagonal as photon absorbers. The MnS were prepared using (a-c) bis(N‐Piperl‐N‐p‐anisildithiocarbamato)Manganese(II) Complexes Mn[N-Piper‐N‐p‐Anisdtc] as (MnS_1), N‐p-anisidinyldithiocarbamato Mn[N‐p-anisdtc] as (MnS_2) and N‐piperidinyldithiocarbamato Mn[N‐piperdtc] as (MnS_3). The corresponding passivated films were denoted as CM-1, CM-2, and CM-3. The influence of passivation on the structural, optical, morphological, and photochemical properties of the prepared devices has been investigated. Raman spectra show that the combination of this heterostructure is triggered by the variation in particle size and surface effect, thus resulting in good electronic conductivity. The narrow band gaps could be attributed to good interaction between the passivative materials on the TiO2 surface. CM-2 cells, stability studies show that the cell is polarized and current flows due to electron migration across the electrolyte and interfaces at this steady state. The cyclic voltammetry (CV) curve for the CM-3 with the highest current density promotes the electrocatalytic activity of the assembled solar cell. The catalytic reactions are further confirmed by the interfacial electron lifetimes in the Bode plots and the impedance spectra. The current–voltage (J–V) analysis suggests that the electrons in the conduction band of TiO2/CuS recombine with the semiconductor quantum dots (QDs) and the iodolyte HI-30 electrolyte, resulting in 5.20–6.85% photo-conversions.

Insight into mechanism for remarkable photocatalytic hydrogen evolution of Cu/Pr dual atom co-modified TiO2.

The development of high-activity photocatalysts is crucial for the current large-scale development of photocatalytic hydrogen applications. Herein, we have developed a strategy to significantly enhance the hydrogen photocatalytic activity of Cu/Pr di-atom co-modified TiO2 architectures by selectively anchoring Cu single atoms on the oxygen vacancies of the TiO2 surface and replacing a trace of Ti atoms in the bulk with rare earth Pr atoms. Calculation results demonstrated that the synergistic effect between Cu single atoms and Pr atoms regulates the electronic structure of Cu/Pr-TiO2, thus promoting the separation of photogenerated carriers and their directional migration to Cu single atoms for the photocatalytic reaction. Furthermore, the d-band center of Cu/Pr-TiO2, which is located at -4.70 eV, optimizes the adsorption and desorption behavior of H*. Compared to TiO2, Pr-TiO2, and Cu/TiO2, Cu/Pr-TiO2 displays the best H* adsorption Gibbs free energy (-0.047 eV). Furthermore, experimental results confirmed that the photogenerated carrier lifetime of Cu/Pr-TiO2 is not only the longest (2.45 ns), but its hydrogen production rate (34.90 mmol g-1 h-1) also significantly surpasses those of Cu/TiO2 (13.39 mmol g-1 h-1) and Pr-TiO2 (0.89 mmol g-1 h-1). These findings open up a novel atomic perspective for the development of optimal hydrogen activity in dual-atom-modified TiO2 photocatalysts.

Clarifying the Direct Generation of •OH Radicals in Photocatalytic O2 Reduction: Theoretical Prediction Combined with Experimental Validation.

This work systematically studied thermocatalytic and photocatalytic pathways of formaldehyde degradation and H-assisted O2 reduction over a Pt13/anatase-TiO2(101) composite via DFT calculations together with constrained molecular dynamics (MD) simulations. We show that photocatalytic O2 reduction on Pt/TiO2 can directly generate •OH radicals (*O2 → *OOH → •OH) via two hydrogenation steps with small barriers, and the product selectivity (*H2O2 or •OH) is decided by the relative position between catalyst Fermi level and •OH/*H2O2 redox potential (theoretical determination of 0.07 V referencing to the SHE). Such a novel reaction channel was furthermore validated at the liquid-solid interface via constrained MD simulations and experimental electron paramagnetic resonance detections, and a wide range of H resources, e.g., *HCHO, *HCO, *H (H+ + e-), can always drive the direct •OH generation. The additional portion of e--triggered •OH radicals are prone to diffuse into solution or the TiO2 surface and furthermore cooperate with the conventional h+-driven photooxidations.

Modeling adsorption reactions of ammonium perchlorate on rutile and anatase surfaces.

In this work, the effects of two TiO2 polymorphs on the decomposition of ammonium perchlorate (NH4ClO4) were studied experimentally and theoretically. The interactions between AP and various surfaces of TiO2 were modeled using density functional theory (DFT) calculations. Specifically, the adsorption of AP on three rutile surfaces (1 1 0), (1 0 0), and (0 0 1), as well as two anatase surfaces (1 0 1), and (0 0 1) were modeled using cluster models, along with the decomposition of adsorbed AP into small molecules. The optimized complexes of the AP molecule on TiO2 surfaces were very stable, indicating strong covalent and hydrogen bonding interactions, leading to highly energetic adsorption reactions. The calculated energy of adsorption (ΔEads) ranged from -120.23 to -301.98 kJ/mol, with highly exergonic calculated Gibbs free energy (ΔGads) of reaction, and highly exothermic enthalpy of reaction (ΔHads). The decomposition of adsorbed AP was also found to have very negative ΔEdec values between -199.08 and -380.73 kJ/mol. The values of ΔGdec and ΔHdec reveal exergonic and exothermic reactions. The adsorption of AP on TiO2 surfaces anticipates the heat release of decomposition, in agreement with experimental results. The most common anatase surface, (1 0 1), was predicted to be more reactive for AP decomposition than the most stable rutile surface, (1 1 0), which was confirmed by experiments. DFT calculations show the mechanism for activation of the two TiO2 polymorphs is entropy driven.

Catalytic mechanisms for As(III) oxidation by H2O2 over TiO2 surfaces, and effects of support, vacancy and photoirradiation

As(III) is much more toxic than As(V) while shows apparently lower affinity at minerals surfaces. Oxidation of As(III) to As(V) by H2O2 over anatase surface provides an attractive avenue for pollution control, and the chemocatalytic and photocatalytic mechanisms are unraveled by means of the DFT + D3 approach. Impacts of anatase as support, O2c/O3c vacancy, photoirradiation are addressed as well. As(III) oxidation under various reaction conditions leads to As(V) through dual electron transfers, while energy barriers differ substantially and decline as 1.80 (direct oxidation) > 1.35 (anatase as support) > 1.24 (O3c vacancy) > 0.50 (chemocatalysis) > 0.28 (photocatalysis) ≥ 0.26 (O2c vacancy) eV. Anatase as support promotes the reaction through bonding with H2O2/As(OH)3 and electron transfers, and its close participation during chemocatalysis produces the TiOOH active site that causes As(III) oxidation to proceed facilely under ambient circumstances. TiOOH exists in two forms (monodentate and bidentate mononuclear) and is critical for chemocatalysis, while its destruction for O3c vacancy exhibits strongly adverse effects to As(III) oxidation. Photoirradiation readily generates the OH• radicals, and corresponding mechanism is plausible while less preferred than the newly posed mechanism based on the Ti(H2O2) active site. Synergism among a number of surface atoms conduces to the superior activity for O2c vacancy and photocatalysis. Results provide a comprehensive understanding for As(III) oxidation to As(V) by H2O2, and facilitate catalysts design for As(III) oxidation that alleviates environmental pollution.

Surface Reconstruction-Induced Photocatalytic Methanol Reduction Reaction on a Rutile TiO2(001) Surface.

Photochemistry of methanol on TiO2 surfaces is of great importance both fundamentally and industrially. Methanol was previously reported only to occur photogenerated hole-participating oxidation reactions on TiO2 surfaces. Herein, we report that, upon UV light illumination, the methoxy species formed by methanol dissociation at the 5-fold coordinated Ti4+ sites (CH3O(a)Ti5c) of a reconstructed rutile TiO2(001)-(1 × 1) surface also undergoes the C-O bond cleavage into methyl fragments mediated by photogenerated electrons, in addition to the well-established photogenerated hole-participating oxidation reactions. Upon subsequent heating, the resulting methyl species undergoes hydrogenation and coupling reactions into methane and ethane, respectively. Accompanying theoretical calculations showed that the lowest unoccupied molecular orbital (LUMO) of CH3O(a)Ti5c is localized almost at the conduction band minimum of the CH3O-adsorbed reconstructed rutile TiO2(001)-(1 × 1) surface, indicating the likely TiO2 → CH3O(a)Ti5c interfacial photoexcited-electron transfer. These results greatly broaden the photochemistry of methanol on TiO2 surfaces and demonstrate a photocatalytic methanol-to-hydrocarbon reaction route.

Fabrication of dye-sensitised solar cell using dry Ixora extract as sensitiser

ABSTRACT A dye-sensitised solar cell was fabricated using dry Ixora flower extract. The sensitiser was obtained by physical extraction using a mixture of ethanol and distilled water as solvent in the ratio of 7:3. The optical study of the sample was done within wavelength range of 230 nm to 1100 nm using spectrophotometer (UV- 750 series). The outcome shows an optimum absorption in the visible region of the EM spectrum, which shifted to the UV region when adsorbed onto a nano-porous TiO2 surface. An alternative peak of 0.95a.u in the visible region was observed with enhanced optical absorption across the infrared region of the spectrum. The absorption coefficient values suggest the extract absorbs light in the visible region, which was also confirmed with the relatively high extinction coefficient observed in the visible region of the EM spectrum. The extract exhibits a low transmittance in the visible range, which increases to over 99% in the red wavelengths. The extract has low reflectance of about 20% in the visible range, which falls lower as wavelength increases into the infrared region. The energy band gap (for direct transition) of 2.13 eV was obtained for dry Ixora dye extract. The fabricated solar cell performed a fill factor of 0.27, Jsc of 0.1273 mA/cm2, Voc of 0.7001 V, and conversion efficiency of about 0.02%. with these results, the dye extract of dry ixora flower can serve as a good photo-sensitiser for the fabrication of dye-sensitised solar cell.

Insights into the impact of self-contained sulfur impurity on the superior photocatalytic activity of UV100

The commercial Hombikat UV100 is a TiO2 photocatalyst that is less studied and used than Aeroxide P25, resulting in limited knowledge associated to it. In this study, we used ICP-OES, XPS, and TGA analyses to show that UV100 contains non-negligible traces of sulfur as-received, which can be migrated to the surface of TiO2 through a simple calcination treatment. Ionic chromatography, DRIFTS, and pyridine-TPD analyses confirmed that a portion of the surface sulfate after the thermal induced migration can be removed by distilled water, along with associated sodium cations, without impacting the surface chemistry of the photocatalyst. Calcination of UV100 enhanced the photocatalytic activity in the liquid-phase degradation of phenol, paracetamol, and chloramphenicol, and this activity remained relatively unaffected by the leaching of sulfate. Although EPR indicated that surface-bound sulfate might act as electron trapping centers or oxygen chemisorption centers, the primary reason for the improved photocatalytic activity is likely the increased crystallinity of the anatase phase due to high-temperature calcination, aided by sulfur’s retarding effect on the anatase-to-rutile transition.

Probing the Photocatalytic Pathways of Iron (III) Protoporphyrin IX-Functionalized TiO2: A Study on Oxo-Iron(IV) Porphyrin π-Cation Radical Formation

The presence of phenolic compounds in aquatic environments, resulting from industrial activities such as coal processing and petroleum refining, poses significant concerns due to their adverse effects on water safety, even at minimal concentrations. These compounds present challenges during remediation using traditional techniques such as solvent extraction, biological treatments or chemical oxidations. In response to these challenges, Advanced Oxidation Processes have emerged as a promising solution, with methods like heterogeneous photocatalysis, ozonation, sonification and so on, showing potential for degrading persistent organic molecules[1] [2].Titanium dioxide (TiO2) has gained importance in environmental remediation due to its ease of synthesis, cost-effectiveness, and versatility. Its unique properties, including exceptional chemical stability and non-toxic nature, make it suitable for water purification among other applications. Several studies aim to extend responsiveness of TiO2 beyond UV-A radiation, seeking to harness the wider and more prevalent visible light spectrum. This endeavor is driven by the desire to optimize the utilization of solar energy in various applications. To enhance TiO2 absorption of visible light, alternative chromophores, particularly porphyrins, are employed. Porphyrins, known for their extended lifespan in the excited state and efficient photoabsorption in the visible region, serve as excellent sensitizers when combined with TiO2, enabling effective charge separation[3].This study explores the activity enhancement of TiO2 catalyst by incorporating iron (III) protoporphyrin IX (FePPIX). The objective is to understand how hydrogen peroxide (H2O2), generated through photocatalysis on the TiO2 surface, influences the formation of oxo-iron(IV) porphyrin π-cation radicals. These radicals specifically form through the interaction with iron porphyrin attached to TiO2, offering a unique pathway for efficiently degrading phenolic compounds, as is proposed in Figure 1. The investigation underscores the significance of TiO2 surface sensitization and the simultaneous emergence of porphyrin radicals in shaping the dynamics of the photocatalytic process.We fabricated TiO2 nanotube sheets (TiO2-NTs) by anodizing metallic titanium sheets and then functionalized them with FePPIX. The process involved degreasing, chemical cleaning, anodization, exfoliation, and thermal treatment for anatase phase formation. Additionally, we utilized anatase-TiO2 nanoparticles. We carried out functionalization, which included ozone exposure, UV-C light treatment, and immersion in an acidic FePPIX solution in methanol, reacting with the hydroxylated surface induced by ozone treatment. After functionalization, we carefully washed away the excess iron protoporphyrin with methanol, and we air-dried the materials at room temperature. We comprehensively characterized the nanomaterials using diverse analytical techniques, including Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR), Raman and UV-Vis spectroscopies, and ESR analyses. We further investigated the photogeneration of hydroxyl radicals (•OH) on FePPIX-functionalized and non-functionalized TiO2 nanotube arrays through the photobleaching of N-N-dimethyl-4-nitrosoaniline. Additionally, we studied phenol degradation under UV irradiation. Our findings provide detailed insights into the physical and chemical properties, morphology, and composition of the fabricated nanomaterials.The SEM images reveal well-defined nanotube arrays, underscoring the efficacy of the fabrication technique. Energy-Dispersive X-ray Spectroscopy mapping further solidifies this observation, confirming a uniform distribution of iron in functionalized nanoparticles and supporting the success of functionalization. FTIR and Raman spectroscopy provide detailed insights into the presence of functional groups and vibrational modes, establishing the success of the functionalization process as well. Tauc plots show a narrowed energy gap in functionalized nanotubes, hinting at their potential for visible light activity.Photocatalytic assessments uncover diminished behavior, with lower •OH generation rates observed under UV-A light for functionalized nanotubes but notable activity under visible light, aligning with the reduced band gap energy. Furthermore, enhanced phenol degradation on functionalized nanotubes under UV-A light, potentially associated with compound I, introduces complexity to the photocatalytic pathways. The application of ESR study confirms the presence of paramagnetic species, such as [PPFeIV=O]+•, thereby highlighting the influence of protoporphyrin on the TiO2 surface and its integral role in photocatalysis.In summary, the study confirms successful TiO2 nanomaterial functionalization with FePPIX, promising applications in environmental remediation. Analyses validate binding with hydroxyl groups, Tauc plots indicate enhanced photocatalytic activity under visible light, and ESR analysis suggests the presence of paramagnetic species that could improved phenol degradation. Further investigation is needed for a comprehensive understanding. Overall, these findings hold potential for efficient and sustainable wastewater treatment.[1] S. Rasalingam, R. Peng, R. T. Koodali, J. Nanomater. 2014, 617405.[2] Y. Deng, R. Zhao, Curr Pollut. Rep 2015, 1, 167.[3] C. C. Huang, P.S. Parasuraman, H. C. Tsai, J. J. Jhu, T. Imae, RSC Adv. 2014, 4, 6540. Figure 1

Using Atomic Layer Deposition to Create Mixed Metal Oxide Electrodes for H2O2 Generation through Water Oxidation

The electrochemical synthesis of H2O2 through water oxidation provides a means of producing a useful chemical and potential fuel without the input of fossil fuels. Highly stable metal oxides like TiO2 and SnO2 surfaces have shown activity as electrocatalysts for oxidative H2O2 generation, but often require high overpotentials that result in parasitic side reactions. Using atomic layer deposition (ALD) to introduce well-distributed layers of MnOx dopant one can lower the required overpotential of TiO2 and SnO2 surfaces for H2O2 production. Even a single sub-surface layer of MnOx can alter the redox behavior of a 5 nm thick oxide film. While the doped films maintained reversible Mn redox peaks and prevent the total dissolution of the deposited Mn, in-situ inductively coupled mass spectrometry did reveal loss of Mn from the film at applied potentials close to the expected onset potential of the 2e- water oxidation reaction. The depth of sub-surface MnOx was varied to determine the effect on both electrode activity, selectivity, and stability. In addition, the use of either inert and oxidizing annealing atmospheres was used to control both the distribution and the charge-state of the Mn species. This work provides some indication of how manganese-doped metal oxide electrodes degrade during operation and how controlling the surface can improve the activity and stability of the device. This study may also provide a framework of how other redox active species can be embedded within more stable oxide matrices using ALD methods to maximize stability and activity.

(Invited) Computational Models of Proton-Coupled Electron Transfer in Energy Conversion and Storage

Proton-coupled electron transfer (PCET) is a fundamental class of chemical reactions that is central to many electrochemical energy conversion and storage processes. In this talk, I will discuss recent theoretical model development for interfacial and intermolecular PCET reactions. First, I will describe a rate constant model for the reaction between reduced anatase TiO2 surfaces and a 4-MeO-TEMPO nitroxyl radical. The rate constants are modeled using vibronically nonadiabatic PCET theory, where the transferring proton and electron are treated quantum mechanically. Hybrid functional periodic density functional theory (DFT) calculations are used to derive model parameters such as driving forces, reorganization energies, and proton vibrational wavefunctions. This modeling strategy highlights the role of inner-sphere bond reorganization and excited vibronic states on the PCET reactivity of metal oxides. Next, I will show how similar computational approaches can be used to predict whether electrochemical PCET is likely to proceed through concerted electron–proton transfer or sequential electron transfer and proton transfer steps. Using PCET reactions between redox-active quinones and functionalized imidazole bases as an example, mechanistic predictions are informed by DFT-calculated potential energy surfaces. These PCET modeling strategies have broad applicability to kinetic studies of electrochemical energy conversion and storage processes.

Wettability of anatase TiO2 surface: Effect of niobium doping

The effect of niobium doping on the hydrophilic behavior of anatase TiO2 surface was demonstrated on a series of x-Nb-TiO2 nanocoatings with dopant concentrations in the range of 0.0 - 1.0 at.% Nb. Thin films prepared on glass substrates from sols by dip-coating were characterized by tensiometric, work function and isoelectric point measurements along with FT-IR spectroscopy in situ method. Using macroscopic and microscopic techniques, it was found that, at low doping level, it is the functionalization of the anatase surface with niobium ions that leads to a drastic change in its surface acid-base as well as electronic properties and, as a consequence, to a sharp increase in the initial surface hydrophilicity. The rearrangement in the hydroxyl‑hydrated layer with the formation of additional hydroxyl groups as a result of surface functionalization has an increased effect on wettability only at low levels of niobium inclusion, whereas with increasing dopant content the electronic factor plays a significant role on the properties of titanium dioxide, including its wettability. The kinetic dependencies of the photoinduced superhydrophilic conversion for all Nb-doped titanium dioxide surfaces were obtained and discussed in terms of proposed mechanism. Both the initial hydrophilic state and the initial rate of photoinduced hydrophilic conversion depend on the Nb concentration in titanium dioxide, while the final UV-induced superhydrophilic state is achieved for all Nb-doped TiO2 regardless of the dopant content.

Solid-state NMR of active sites in TiO2 photocatalysis: a critical review

Titanium dioxide (TiO2) is one of the optimal semiconductor metal oxide photocatalysts with a wide range of application fields, such as heterogeneous catalysis, energy science, and environmental science. Solid-state nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for characterizing both structure and dynamics at an atomic-molecular level in heterogeneous catalysts. In this review, we first provide a brief discussion on the progress in investigating the structures of titanium and oxygen in bulk and on the surface of TiO2 by using various solid-state NMR techniques. Advances in the understanding of electronic structure and properties of TiO2 with distinct surface features, including various crystal facets and heteroatomic adsorption by chemical probe-assisted NMR techniques, are secondly presented. The solid-state NMR characterization of heteroatom active sites (such as 13C, 15N, 11B, 27Al) and their function in TiO2 photocatalysts is described in detail. Finally, a critical discourse assesses the current limitations and prospects of solid-state NMR in its application to the optimization and design of advanced TiO2 photocatalysts.

Construction of nanocomposite hydrogel by TiO2-carbon quantum dots encapsulated in alginate with a highly efficient adsorption and photodegradation of dye pollutants

This presentation introduces an integrated photocatalyst/adsorbent system, achieved through immobilization and encapsulation of the TiO2 doped with CQDs (carbon quantum dots) nanocomposite within the calcium alginate (CaAlg) matrix. The nanoparticles and nanocomposites were analyzed using various techniques, including FE-SEM, EDX, TEM, XRD, PL, FT-IR, BET, and UV–vis DRS, to determine their structure and properties. The TiO2/CQDs/Alg nanocomposite hydrogel considerably influenced the adsorption and photocatalytic degradation of methylene blue (MB) as a dye pollutant. The adsorption studies were conducted to assess parameters such as adsorption capacity, kinetic behavior, and adsorption isotherms. The outcomes revealed a high adsorption capacity (44.13 mg/g at 90 min) and indicated that the pseudo-second-order kinetic model was highly suitable for describing the adsorption behavior of MB. Moreover, the Freundlich isotherm exhibited better fitting capabilities compared to the Langmuir isotherm. CQDs not only facilitated the transfer of photoelectrons from the TiO2 surface, preventing recombination of electron-hole pairs but also enhanced visible light absorption by the upconversion photoluminescence. The TiO2/CQDs/Alg displayed excellent photodegradation performance (97 %) of MB compared with TiO2 and TiO2/CQDs under visible light due to the abundance of active sites for MB adsorption and photocatalytic reactions. The TiO2/CQDs/Alg hydrogel exhibited excellent reusability in degrading MB for up to five consecutive cycles and showed significant swelling behavior across a broad pH range, reflecting the hydrogel's exceptional stability. The use of charge carrier scavengers indicated that O2˙−radicals were the primary surface species involved in the photodegradation of MB.

Facile hydrothermal synthesis of ZnIn2S4/TiO2 nanosheets for promoted hydrogen evolution reaction

The current study was conducted by introducing a narrow bandgap semiconductor, ZnIn2S4, with the goal of addressing the inefficiency of hydrolysis dissociation and the limited visible light absorption capacity faced by TiO2 as a hydrogen evolution reaction (HER) catalyst due to its low conduction band position and wide bandgap. Using a one-step hydrothermal process, ZnIn2S4 nanosheet/TiO2 nanorod heterostructures were built on nickel foam substrates. The nanosheet structure of ZnIn2S4 is shaped like a flower, which greatly increased the roughness of the TiO2 surface and revealed additional active sites. The ZnIn2S4/TiO2 heterostructure demonstrates quick reaction kinetics and effective electron transport capability, as demonstrated by the electrochemical test results. An overpotential of just 195 mV is required to obtain a current density of 10 mA cm−2. In addition, the overpotential is further decreased to 160 mV under simulated solar radiation. Furthermore, ZnIn2S4 addition minimizes the free energy of hydrogen adsorption on the TiO2 surface and optimizes the position of its Fermi energy level, improving the usage of photogenerated carriers, according to density functional theory (DFT) calculations. This work validates the prospective use of ZnIn2S4/TiO2 heterostructures in photoelectrocatalysis and offers a fresh viewpoint for developing high-performance HER catalysts.

Insight of indium single atom loading on TiO2 for remarkable photocatalytic hydrogen evolution

Hydrogen production by photocatalysis water splitting is an attractive and promising development method, but the current efficiency is too low for application. Loading single atoms can significantly enhance the photocatalytic efficiency, however, the insightful understanding of the impact of single atom loading on catalytic performance is still ambiguous. In this work, InSA/TiO2 photocatalysts modified with indium single atom (InSA) were synthesized by photo-deposition process. Under 300W Xe lamp illumination, the hydrogen production rate of the optimized InSA/TiO2 photocatalyst achieves 6.11 mmol g−1 h−1, which is 7.6 times that of TiO2 prepared under the same conditions. The results of characterization analysis and density functional theory (DFT) calculations indicate that some of the Ti atoms on the TiO2 surface are replaced by the doped In, and the local electronic structures of the photocatalyst are regulated, which results in effectively separating of the photo-generated carriers, and significant increasing the activity of the surrounding unsaturated oxygen, thus, the photocatalytic hydrogen production performance is effectively improved. This work provides a strategy to improve photocatalytic activity, and also deepens the understanding of metal single atom modification mechanism.

Enhancing CO2 reduction with formamide-Ni@TiO2 catalyst

Formamide condensation with Ni can generate the NC structure, widely recognized as an efficient catalyst for electrocatalytic CO2 reduction reaction (CO2RR). To improve the utilization efficiency of Ni atoms, we introduced metal oxides as substrates to modulate the growth of a formamide-Ni (FA-Ni) condensate. FA-Ni@TiO2 demonstrated 2.8 times higher partial CO current density and Ni turnover frequency than FA-Ni, which were also higher than those of other FA-Ni@metal oxides, including ZrO2, Al2O3, Fe2O3, and ZnO. The improved performance of CO2RR can be attributed to the Ni content exposed on FA-Ni@TiO2 being twice that of the raw FA-Ni condensate. The Fourier transform infrared results suggested that formamide was adsorbed on TiO2 via the -CHO group, exposing -NH2 for potential interaction with Ni. As a result, Ni atoms were predispersed on the TiO2 surface. By contrast, the dispersion of Ni atoms was not enhanced by other metal oxides, such as Al2O3, Fe2O3, and ZnO, owing to the robust acidity of their surface sites. These metal oxides adsorbed formamide via -NH2, leading to the absence of extra -NH2 available for binding to Ni atoms. This study provides new insights into the development of appropriate substrates for single-atom catalysts.

Reticulated mesoporous TiO2 scaffold for self-cleaning surfaces

Interest in self-cleaning coatings is rising due to their potential to enhance comfort and quality of life in polluted urban environments, driving the search for materials with optimal physical properties. Convergent with this goal, this study investigates the wetting properties and photo-catalytic efficiency of reticulated TiO2 layers. It shows that these properties are significantly influenced by the topographical characteristics of the TiO2 surface, which can be precisely controlled through variations in pulverization pressure and low-temperature post-annealing treatments. Post-deposition annealing of the TiO2 layers achieves 100 % self-cleaning efficiency for both thick and thin films, with optical transmission ranging from approximately 60 %–80 % in the visible spectrum. Additionally, the TiO2 layers exhibited promising capabilities for eliminating pathogenic microorganisms and disinfecting surfaces. The underlying causal factors of these remarkable and technologically promising surface features are explored and discussed.

Stable and efficient chlorine evolution reaction with atomically dispersed Ru on surface tensile strained TiO2

Developing highly efficient and selective electrocatalysts for the chlorine evolution reaction (CER) in the chloralkali industry is of great importance. Here, we report the discovery of a new electrocatalyst for CER consisting of atomically dispersed Ru sites on surface tensile strained TiO2 (Ru-S-TiO2). The single-atom Ru species were stabilized on the strained TiO2 surface by strong metal-support interactions. The Ru-S-TiO2 is highly efficient, initiating CER at only 5 mV above the ECER, and has shown excellent stability for over 100 hours. It exhibited >95 % CER selectivity even in acidic media with low Cl− concentrations (0.2 M). Our results demonstrate that the strong metal-support interactions between the atomically dispersed Ru species and the strained TiO2 surface are crucial for the high catalytic activity, selectivity, and stability of Ru-S-TiO2 for CER. Ru-S-TiO2 holds great promise as a viable alternative to existing mixed metal oxides-based electrocatalysts for CER in the chloralkali industry.