TiO2 Support Research Articles

Catalytic oxidation of CO over CuO@TiO2 catalyst: The relationship between activity and adsorption performance

AbstractThe emission of CO toxic gases seriously endangers environmental safety and human health. At present, the use of catalysts for catalytic oxidation of CO has become the mainstream research direction. In this study, CuO@TiO2 catalysts with different ratios were prepared by solvent hydrothermal method, and the effects of reaction pretreatment temperature and other factors on the catalytic oxidation performance of CO were investigated. The experimental results show that the catalyst can achieve 100% conversion of CO at 115°C under the condition of pretreament at 350°C for 2 h. This excellent performance is due to the uniform distribution of the active component on the surface of the TiO2 support, and the large pore structure constructed by the solvent hydrothermal method enhances the adsorption and activation of CO. This work provides an idea for the preparation of CO oxidation catalysts.

Enhanced Photodegradation of Congo Red Using RSM‐Optimized TiO₂ on Borassus flabellifer Male Inflorescence Biochar

AbstractThis study explores the use of biochar, derived from Borassus flabellifer male inflorescence biomass as an alternative support for titanium dioxide (TiO2) to enhance its photocatalytic activity in degrading Congo red (CR) dye pollutant. The biochar was synthesized through controlled pyrolysis and subsequently combined with TiO2 to form a nanocomposite via hydrothermal method. The primary goal of creating this nanocomposite is to breakdown azo dyes, such as CR, using UV irradiation. Comprehensive characterization techniques, including XRD, FTIR, SEM coupled with EDAX, XPS, and UV‐DRS confirmed the successful integration of biochar with TiO2. The enhanced photocatalyst performance is attributed to the increased surface area, improved light absorption, and efficient charge separation facilitated by the biochar support. Furthermore, the experimental parameters were optimized using the response surface methodology (RSM). These studies demonstrated that the CR concentration, contact duration, pH, and photocatalyst quantity are critical factors in the photocatalytic oxidation process. The strong correlation coefficient for the first order model indicated that the data described by the RSM, agreed with the obtained results. This study highlights the potential of agricultural waste‐derived biochar as a cost‐effective and sustainable support for TiO₂, offering a viable solution for the remediation of dye‐contaminated water.

Reevaluation of XPS Pt 4f peak fitting: Ti 3s plasmon peak interference and Pt metallic peak asymmetry in Pt@TiO2 system

The structural, electronic, and electrochemical properties of noble metals supported on transition metal oxides, such as Pt nanoparticles (NPs) supported on TiO2 (Pt@TiO2), have been extensively studied for their relevance to energy technologies, including photocatalysis, electrocatalysis, and electrochemical energy conversion. As the need to lower the amount of Pt and other noble metals used in energy conversion systems becomes urgent, it is essential to accurately quantify the loading of these metals and electronic density redistribution between them and their supports. X-ray photoelectron spectroscopy (XPS) is widely used for the identification and quantification of chemical species. In particular, fitting of the Pt 4f spectra for Pt@TiO2 is frequently performed to determine the chemical environment and oxidation state of Pt, which strongly affect the physical behavior and catalytic performance of this system. Here, we show that neglecting contributions due to the Pt surroundings and the asymmetry of the Pt metal peak in the line shape fitting can lead to severe mischaracterization of the oxidation state of Pt. We quantify the effects of background contributions that stem from the TiO2 support and discuss how factoring in the strong asymmetry of Pt 4f doublets, which stems from the shake-up type processes, affects the interpretation of Pt 4f XPS line shape.

Atomically dispersed ruthenium single-atom alloy catalysts enabling efficient iodide oxidation reaction electrolysis in acidic media

Single-atom catalysts exhibit immense potential across diverse reactions, yet their synthesis and stability in acidic environments pose significant challenges. Herein, we introduce a facile one-step hydrothermal approach to fabricate Ru single-atom alloy catalysts (Ru SAAC) through the reaction of Ru and Ti precursors, followed by annealing in an argon atmosphere. Analysis via extended X-ray absorption fine structure spectroscopy and aberration-corrected scanning transmission electron microscopy confirms the atomically dispersed Ru alloy catalyst anchored on a TiO2 support. Remarkably, Ru SAAC demonstrates exceptional electrocatalytic performance in the iodide oxidation reaction (IOR), achieving a benchmark current density of 10 mA/cm2 at a mere voltage of 0.64 V in acidic conditions within a three-electrode electrolyzer setup. Surpassing nanoscale Ru/TiO2 and RuO2/TiO2 counterparts, Ru SAAC exhibits the highest voltage efficiency (84.4%), lowest Tafel slope (36 mV/dec), and lowest overpotential (100 mV) under identical experimental conditions. This method enables facile control over Ru morphology. It enhances the kinetics and thermodynamic favorability of Ru SAAC in acidic media, opening avenues for synthesizing diverse transition metal-based single-alloy catalysts for varied applications.

Laser-engraved defects in TiO2 support: Enhancing reducibility and redox capability of Pt/TiO2 catalyst for reactive and selective hydrogenation

Titanium dioxide (TiO2) has been studied as catalyst or catalyst support in catalysis. Its synthesis or modification approach controls the structural, optical, and electronic properties. Here we applied laser engraving to the anatase TiO2 and studied the consequent changes in its structure and property as well as the properties of TiO2 supported platinum (i.e., Pt/TiO2) catalyst. The laser engraving enlarged the particle size, formed rutile phase and created defects (i.e., oxygen vacancy (Ov) and Ti3+) in anatase TiO2. This induced band gap change and enhanced visible light absorption. The defects created by laser engraving are stable and more reducible than those existed in the pristine TiO2. The defective TiO2 is structurally stable and has great redox properties. The metal-support interaction in the Pt/defective TiO2 catalyst is stronger than that of the pristine Pt/TiO2 catalyst, which enabled higher reactivity and selectivity in hydrogenation of 3-nitrostyrene and furfuryl alcohol. Laser-engraved TiO2 has been rarely studied for thermal catalysis. This work provides basic understanding of material properties and catalysis application of laser-engraved catalyst supports and catalysts in field of thermal catalysis.

Effect of the RhnNin alloy cluster size on the catalytic performance of RhnNin/TiO2 in the conversion of syngas to ethanol

The direct conversion of syngas to ethanol on the RhnNin/TiO2 (n = 1, 2, 3, 4) catalyst has been investigated by using the density functional theory (DFT) and micro-kinetic methods, in order to elucidate the regulatory mechanism of RhnNin alloy cluster size-induced metal-support interaction on the catalytic performance of RhnNin/TiO2 in the ethanol synthesis. The results indicate that Rh1Ni1/TiO2 and Rh3Ni3/TiO2 can significantly enhance the conversion of CO and the formation of C–C bond and meanwhile inhibit the generation of methane. Rh1Ni1/TiO2 exhibits the highest ethanol production activity and relative selectivity. The electronic property analysis results suggest that Ni atoms on the alloy clusters and Ti and O atoms on the supports transfer the most charge to the Rh atoms on the Rh1Ni1/TiO2 catalyst, which displays the strongest Rh-Ni interaction on the alloy clusters as well as the strongest interaction between the alloy clusters and the TiO2 support, endowing Rh1Ni1/TiO2 with the highest catalytic activity. In addition, the Ab-initio molecular dynamics (AIMD) simulations at 525 K show that the Rh1Ni1/TiO2 catalyst has high thermal stability.

Modulating d-p-band electron coupling by N-doping for promoting CuSAs-N/TiO2 photocatalytic hydrogen evolution

Doping can effectively improve the light absorption of single-atoms photocatalysts, but the metal-support interaction (MSI) and surface electronic structure will change due to doping, which needs further study. Herein, we report a nano-TiO2 co-modified with internal doping of N and surface loading of Cu single atoms (CuSAs-N/TiO2) for photocatalytic water-splitting hydrogen evolution. Experimental and theoretical studies confirm that the internal doped N can interact strongly with the surface-loaded CuSAs by modulating the d-p-band electronic coupling. The enhancement of d-p-band electronic coupling enhances the strong electron interaction between CuSA and support of N-doped TiO2. Especially, it significantly affects the d-p-band electronic structure of the catalyst surface lattice and causes electron redistribution in the local structure of surface CuSAs, which can optimize the surface hydrogen evolution kinetics and promote hydrogen production. Consequently, the photocatalytic hydrogen evolution activity, photoelectric response rate and light energy utilization of CuSAs-N/TiO2 are significantly improved. This work reveals the fundamental necessity of d-p-band electron coupling in MSI and catalyst surface electronic structure for driving solar water splitting. It provides valuable insights for the rational design of metal single-atom photocatalysts with high activity and efficient light energy utilization.

Synergistic removal of NO and CO in industrial waste gas by Fe-modified Cu/TiO2 catalysts: The synergistic effect of metal oxides interaction

NH3-based selective catalytic reduction (NH3-SCR) combined with carbon monoxide (CO) catalytic oxidation is a productive way to synergistically remove nitrogen oxides (NOx) and CO from industrial waste gas. Catalyst is the undoubtedly centerpiece of the synergistic removal technology, which has aroused tremendous attention. Herein, in this investigation a variety of Cu/TiO2 catalysts modified by various metal oxides were prepared by impregnation method, and the excellent synergistic removal performance of Fe-modified Cu/TiO2 catalyst was observed. The Cu/TiO2 catalyst with a 7 wt% Fe doping amount exhibited the highest NO and CO removal efficiency (86 % for NO at 300 °C and over 98 % for CO from 300 ∼ 400 °C). Through a series of characterization techniques, it was discovered that Cu and Fe oxides interacted to evenly distribute them throughout the surface of TiO2 support, resulting in smaller particle size and abundant variable valence species (Cu+/Cu2+ and Fe2+/Fe3+) to enhance the redox performance of the catalysts. Moreover, the creation of additional surface chemisorbed oxygen, the adsorption of NO and CO, and the improvement of surface acidity were all facilitated by the electron transfer between various Cu and Fe species. In addition, in-situ diffuse reflectance infrared transform spectroscopy (in situ DRIFTS) results revealed the interaction between NH3-SCR and CO oxidation. This study proposes a viable approach to develop efficient catalysts for the synergistic removal of NO and CO in industrial applications.

A Tandem Catalysis for Isoindolinone Synthesis over Single-Atom Pd/TiO2 Catalyst.

Developing an efficient strategy to replace the conventional synthesis method for producing isoindolinone (IIO) scaffold, a crucial structural motif for constructing pharmaceutical molecules, remains to be a great challenge. Herein, a single-atom Pd/TiO2 tandem catalysis has been developed for the IIO scaffold synthesis by using readily available phthalic anhydride (PA), ammonia, and H2. The single-atom Pd/TiO2 catalyst demonstrates superior catalytic performance, achieving a PA conversion of 99 %, an IIO selectivity of 91 %, and a turnover frequency (TOF) up to 4807 h-1. This exceptional performance can be attributed to the tandem catalysis between TiO2 support and single-atom Pd. The TiO2 efficiently catalyzes the conversion of PA with ammonia to form phthalimide (PAM), subsequently transformed into IIO over TiO2 through the reaction of PAM with NH3 and the spillover hydrogen species derived from single-atom Pd. Notably, NH3 functions not only as a reactant but also as a promoter to accelerate the reduction of amides combined with the Pd/TiO2 catalyst. This tandem catalysis of a single-atom Pd/TiO2 catalyst provides a promising strategy for the synthesis of the crucial IIO platform molecules.

Regulating crystal phase of TiO2 to enhance catalytic activity of Ni/TiO2 for solar-driven dry reforming of methane

Ni/TiO2 catalyst is widely employed for photo-driven DRM reaction while the influence of crystal structure of TiO2 remains unclear. In this work, the rutile/anatase ratio in supports was successfully controlled by varying the calcination temperature of anatase-TiO2. Structural characterizations revealed that a distinct TiOx coating on the Ni nanoparticles (NPs) was evident for Ni/TiO2-700 catalyst due to strong metal-support interaction. It is observed that the TiOx overlayer gradually disappeared as the ratio of rutile/anatase increased, thereby enhancing the exposure of Ni active sites. The exposed Ni sites enhanced visible light absorption and boosted the dissociation capability of CH4, which led to the much elevated catalytic activity for Ni/ TiO2-950 in which rutile dominated. Therefore, the catalytic activity of solar-driven DRM reaction was significantly influenced by the rutile/anatase ratio. Ni/TiO2-950, characterized by a predominant rutile phase, exhibited the highest DRM reactivity, with remarkable H2 and CO production rates reaching as high as 87.4 and 220.2 mmol/(g·h), respectively. These rates were approximately 257 and 130 times higher, respectively, compared to those obtained on Ni/TiO2-700 with anatase. This study suggests that the optimization of crystal structure of TiO2 support can effectively enhance the performance of photothermal DRM reaction.

Strong Metal‐Support Interaction Triggered by Molten Salts

Strong metal‐support interaction (SMSI) plays a vital role in tuning the geometric and electronic structures of metal species. Generally, a high‐temperature treatment (>500 °C) in reducing atmosphere is required for constructing SMSI, which may induce the sintering of metal species. Herein, we use molten salts as the reaction media to trigger the formation of high‐intensity SMSI at reduced temperatures. The strong ionic polarization of the molten salt promotes the breakage of Ti‐O bonds in the TiO2 support, and hence decreases the energy barrier for the formation of interfacial bonds. Consequently, a high‐intensity SMSI state is achieved in TiO2 supported Ir nanoclusters, evidenced by a large number of Ir‐Ti bonds at the interface, at a low temperature of 350 °C. Moreover, this method is applicable for triggering SMSI in various supported metal catalysts with different oxide supports including CeO2 and SnO2. This newly developed SMSI construction methodology opens a new avenue and holds significant potential for engineering advanced supported metal catalysts toward a broad range of applications.

Strong Metal-Support Interaction Triggered by Molten Salts.

Strong metal-support interaction (SMSI) plays a vital role in tuning the geometric and electronic structures of metal species. Generally, a high-temperature treatment (>500 °C) in reducing atmosphere is required for constructing SMSI, which may induce the sintering of metal species. Herein, we use molten salts as the reaction media to trigger the formation of high-intensity SMSI at reduced temperatures. The strong ionic polarization of the molten salt promotes the breakage of Ti-O bonds in the TiO2 support, and hence decreases the energy barrier for the formation of interfacial bonds. Consequently, a high-intensity SMSI state is achieved in TiO2 supported Ir nanoclusters, evidenced by a large number of Ir-Ti bonds at the interface, at a low temperature of 350 °C. Moreover, this method is applicable for triggering SMSI in various supported metal catalysts with different oxide supports including CeO2 and SnO2. This newly developed SMSI construction methodology opens a new avenue and holds significant potential for engineering advanced supported metal catalysts toward a broad range of applications.

TiO2-Supported Catalysts in Low-Temperature Selective Reduction of NOx with NH3: A Review of Recent Progress

Selective catalytic reduction (SCR) stands out as a pivotal method for curbing NOx emissions from flue gas. The support, crucially, for SCR efficacy, loads and interacts with the active components within the catalyst. The catalysts could be amplified by the denitration performance of the catalyst by enhancements in support pore structure, acidity, and mechanical robustness. These improvements ensure efficient interaction between the support and active materials, thereby optimizing the structure and property of the catalysts. TiO2 is the most commonly used support of the NH3-SCR catalyst. The catalyst with TiO2 support has poor thermal stability and a narrow temperature range, which can be improved. This paper reviews the research progress on the effects of various aspects of TiO2 support on the NH3-SCR catalyst’s performance, focusing on the TiO2 crystal type, TiO2 crystal surface, different TiO2 structures, TiO2 support preparation methods, and the effects of TiO2-X composite support on the NH3-SCR catalyst’s performance. The reaction mechanism, denitrification performance, and anti-SO2/H2O poisoning performance and mechanism of TiO2 support with different characteristics were described. At the same time, the development trend of the NH3-SCR catalyst using TiO2 as the support is prospected. It is hoped that this work can provide optimization ideas for SCR catalyst research.

Electronic interaction between sub-nanometric Ru entity and TiO2 support regulates the hydrogenation chemistry for selective C-O bond cleavage

Selective C-O bond cleavage without ring saturation is the pillar pursuit in the hydrotreating process for lignin valorization/depolymerization since it avoids the consumption of excessive hydrogen. In this work, the sub-nanometric cluster and nanometric particle of Ru were supported on TiO2 for the hydrogenolysis of C-O bond in aromatic ether. The experimental and theoretical results reveal that, in the catalyst of larger Ru nanoparticles, less electron transfer occurs from individual Ru atom to TiO2, making the Ru-related domains retain the nature of bulky Ru for deep hydrogenation. Sub-nanometric Ru cluster shows more intense electron transfer for individual Ru atom, leading to a stronger modification to Ru domain by TiO2. Such electronic hybridization makes Ru gain the catalytic property of TiO2 to attenuate the activation of aromatic ring, inhibiting ring saturation with maintained C-O cleavage activity. This work implies that further decrease of Ru entity size to single-atom level may achieve the complete inhibition of ring saturation.

Value-Added Electrolysis Hydrogen Production Via Methanol Oxidation over a Synergetic Pt1-W Dual-Site Catalyst

Electrochemical water splitting is a promising way of generating hydrogen for future sustainable green energy source technology options to replace nonrenewable and environmentally pollutant hydrocarbon energy sources. However, due to its high overpotential in oxygen evolution reaction (OER) and low-value product O2, some candidate anodic reactions with low potential should be proposed to replace OER, such as alcohol oxidation. Unlike fuel cell applications, partial oxidation is preferred to achieve high-value products rather than complete oxidation. For this purpose, we design a synergistic effect Pt1-W site on the dual-doped TiO2 support (Ti0.8W0.2NxOy) to catalyze alkaline methanol oxidation and gain 90% selectivity of formate production. Comparing the case of the Pt nanoparticles (69% selectivity of formaldehyde), the Pt single-atom catalyst controls selectivity and enhances the reactivity and stability attributed to the strong catalyst-support interaction. As a result, this work shows a novel strategy for electrochemical hydrogen production at far lower anodic potential by designing a stable and efficient Pt-based single-atom catalyst.

Simultaneously activating molecular oxygen and surface lattice oxygen on Pt/TiO2 for low-temperature CO oxidation

Developing high-performance Pt-based catalysts with low Pt loading is crucial but challenging for CO oxidation at temperatures below 100 °C. Herein, we report a Pt-based catalyst with only a 0.15 wt% Pt loading, which consists of Pt–Ti intermetallic single-atom alloy (ISAA) and Pt nanoparticles (NP) co-supported on a defective TiO2 support, achieving a record high turnover frequency of 11.59 s–1 at 80 °C and complete conversion of CO at 120 °C. This is because the coexistence of Pt–Ti ISAA and Pt NP significantly alleviates the competitive adsorption of CO and O2, enhancing the activation of O2. Furthermore, Pt single atom sites are stabilized by Pt–Ti ISAA, resulting in distortion of the TiO2 lattice within Pt–Ti ISAA. This distortion activates the neighboring surface lattice oxygen, allowing for the simultaneous occurrence of the Mars-van Krevelen and Langmuir–Hinshelwood reaction paths at low temperatures.

Flame made low Pt loading catalysts supported on different metal oxides for catalytic combustion of CO and CH4

Catalytic combustion is an effective approach to remove air pollutants from various emission sources. For this purpose, supported noble metal catalysts are preferred in commercial applications due to their outstanding catalytic activity for eliminating CO, hydrocarbon compounds and NOx. In this paper, we employ the flame spray pyrolysis method to prepare a series of Pt-based catalysts with four different supports (TiO2, ZrO2, MgO and ZnO) and variable low Pt loadings for catalytic combustion of CO and CH4. The performance of 0.5 Pt/TiO2 is the best in all samples, in which the T90 temperatures are 107 and 500 °C for 90% conversion of CO and CH4, respectively. To examine its thermal stability, a time-on-stream test at 700 °C for 420 min is carried out, resulting in a decrease of about 5% in the final conversion of CH4. The X-ray diffraction results show that TiO2 support is a mixed phase with a major amount of anatase and a small amount of rutile other than a pure phase of ZrO2, MgO and ZnO. Furthermore, X-ray photoelectron spectroscopy analysis and high-angle annular dark-field scanning transmission electron microscopy observation show that when the Pt loading is low, the Pt species exist as highly dispersed single atoms on the surface of the TiO2 support. As the Pt loading gradually increases, the state of the Pt species transitions from single atoms to Pt clusters, resulting in a decrease in dispersion. Ultimately, the Pt can successfully accumulate on the surface of the TiO2 nanoparticles, providing abundant active sites for efficient catalytic combustion reactions.

The nature of synergy effects between VOx and TiO2 in low temperature NH3-SCR reaction

In this study, we investigated the low-temperature activity of selective catalytic reduction of NO by NH3 (NH3-SCR) with the effect of different vanadium oxide (VOx) loading in the VOx/TiO2 catalyst. By calculating the specific rate of activity, it was found that the fastest specific rate of activity was achieved when the loading of V2O5 reached 10 wt%, and the nitrogen oxides (NOx) conversion of the above optimal catalyst reached over 80 % in the temperature range of 180–465 °C. The effects of preparation method, calcination temperature, and support on the aggregation state of the vanadium species and the SCR activity of the catalyst were also investigated on the basis of the ideal ratio. Combining the activity and characterization results, it is found that the impregnation method and calcination at 410 °C are more favorable for the moderate dispersion of the vanadium species on the TiO2 surface, producing more highly reactive polymorphic VOx, which is more readily dispersed on the surface of the TiO2 support and interacts more strongly with the TiO2. The interaction between the two can promote the transfer of electrons, resulting in the production of more active O species and low-valent vanadium. The aforementioned species can enhance the catalyst's low- temperature denitrification activity.

In situ photodeposition of ultra-small palladium particles on TiO2.

In situ and operando investigation of photocatalysts plays a fundamental role inunderstanding the processes of active phase formation and the mechanisms ofcatalytic reactions, which is crucial for the rational design of more efficient materials. Using a custom-made operando photocatalytic cell, an in situ procedure to follow the formation steps of Pd/TiO2 photocatalyst by synchrotron-based X-ray absorption spectroscopy (XAS) is proposed. The procedure resulted in the formation of ∼1 nm Pd particles with a much narrower size distribution and homogeneous spreading over TiO2 support compared with the samples generated in a conventional batch reactor. The combination of in situ XAS spectroscopy with high-angle annular dark-field scanning transmission electron microscopy demonstrated the formation of single-atom Pd(0) sites on TiO2 as the initial step of the photodeposition process. Palladium hydride particles were observed for all investigated samples upon exposure to formic acid solutions.

Titanium dioxide heterojunction support design induced robust platinum catalytic hydrogen evolution over wide pH range

The development of efficient hydrogen evolution reaction (HER) electrocatalysts is critical for water splitting. Herein, rutile/anatase titanium dioxide heterojunction supported platinum nanoparticles (Pt-NPs) design with interfacial effect was developed as efficient HER catalyst (Pt@R/A-TiO2) over wide pH range. The R/A-TiO2 support design induces aggregated Pt-NPs on the heterojunction interface. In-situ Raman and in-situ infrared investigations over wide pH range reveal that there exists a strong hydrogen spillover from Pt-NPs to R/A-TiO2 support and fast proton transfer HER kinetics on Pt@R/A-TiO2. Theoretical calculations demonstrate that the R/A-TiO2 heterojunction modulates more electrons transferred from TiO2 support to Pt-NPs, and this electron-rich Pt-NPs weakens H adsorption, thus enhancing the hydrogen spillover effect and improving the HER performance of Pt@R/A-TiO2. In acidic/alkaline/neutral media, Pt@R/A-TiO2 demonstrates excellent HER activity and stability. Especially in acidic media, Pt@R/A-TiO2 exhibits high mass activity of 12.57 A mgPt−1 at an overpotential of 100 mV, which is nearly 11 times higher than Pt/C, and outperforms the recently reported Pt-based catalysts as well. This work advances the design of efficient and stable HER catalysts over wide pH range.