Anatase TiO2 Nanocrystals Research Articles

Organic Ligand‐Free Scalable Dual‐Band Electrochromic Smart Windows

AbstractDual‐band electrochromic (DBEC) smart windows are an emerging energy‐saving technology, especially those constructed from single‐component DBEC materials as they offer an easy way to independently regulate visible (VIS) and near‐infrared (NIR) light. However, the current complicated organic ligand approach used to synthesize single‐component DBEC materials necessitates a post‐annealing treatment, which may severely compromise the scalability of DBEC smart windows. Herein, one organic ligand‐free process is developed to produce well‐controlled Nb‐doped anatase TiO2 nanocrystals (NTO NCs) followed by spraying on arbitrary substrates, giving NTO rigid or flexible films with good DBEC properties and a high optical modulation over 92%. A prototype of a 20 cm × 20 cm DBEC smart window is built. The simplicity and scalability of the synthesis and fabrication process make it a scalable approach to constructing large‐area electrochromic smart windows and foils, with promising applications in fields such as buildings and automobiles.

Photoelectric activity evaluation of surface-loaded ferroferric oxide/titanium dioxide composite prepared from ilmenite

This work demonstrates a surface-loaded Fe3O4/TiO2 composite with the magnetic Fe3O4 deposited on the surface of anatase TiO2 nanocrystal which can be directly prepared from the ilmenite using the coprecipitation method. After the acidolysis treatment with the 95% dissolution rate, the ilmenite will be first transformed into H2TiO3 and FeCl2, and the photoactive anatase TiO2 nanocrystals are obtained from the calcined H2TiO3 at 500[Formula: see text]C. Then a surface-loaded Fe3O4/TiO2 composite TF is finally achieved by the coprecipitation method, which is carefully elaborated to balance the magnetism and photoactivity of Fe3O4/TiO2 composite by the optimal contents of Fe3O4 and TiO2. It is encouraging to note that Fe3O4/TiO2 composite TF shows a good comprehensive performance in serial photodegradation experiments of Rhodamine B. The degradation rate of Rhodamine B is more than 99% during 60 min under the irradiation of both xenon lamp and sunlight. During at least six cycles, the composite TF can show stable photocatalytic activity and good durability together with the recovery and recycling potentials by using an external magnet.

In situ revealing the dehydration and atomic structure evolution of protonated titanate nanotubes via environmental transmission electron microscopy

The precise control of nanomaterial microstructure at the atomic level relies on the comprehensive understanding of atomic structural transition during the fabrication process at the atomic level. The phase transition from protonated titanate to TiO2 is a prevalent route to synthesize low dimensional TiO2-based nanomaterials, which exhibit excellent photocatalytic, lithium-ion battery performances, while the detailed phase transition mechanism remains to be clarified due to lack of atomic-level in situ information. Herein, the atomic structural transitions from one-dimensional H2Ti3O7 (HT) to TiO2(B) and anatase TiO2 (TB and TA) nanocrystals were revealed through in situ environmental transmission electron microscopy, which exhibited a two-step phase transition at 200–600 °C. (I) H2Ti3O7 to TiO2(B) transition began via an indirect pathway at ∼200 °C: The HT (200) interlayer dehydration occurred firstly with lattice shrinkage; Then TB discretely nucleated at the dehydrated H2Ti3O7 nanotube wall with a crystallographic relationship of (200)HT∥(200)TB {[001]HT∥[001]TB}; At higher temperature, the separated nuclei grew up with defects and distorted crystal lattice among them, which then connected and jointed to a single crystalline TB nanotube by atomic rearrangement. (II) The further transition of TiO2(B) to anatase TiO2 occurred via a direct pathway above 400 °C: Scarce nucleation event of TA phase was observed, which generated within TB nanocrystal with a crystallographic relationship of (200)TB∥(002)TA {[001]TB∥[010]TA}. Once a TA nucleus formed, it grew up to a large crystal by consuming the neighbor TB nanocrystals. These findings may contribute to comprehensively understanding phase transition and precisely manipulating the atomic structure of one-dimensional TiO2 nanocrystals.

Electrochemical performance of rice grains like high Mn-doped anatase TiO2 nanoparticles as lithium-ion batteries electrode material

Rice grain-shaped high Mn-doped anatase TiO2(TMO) nanocrystals have been fabricated through redox method at room temperature using several simple chemical reagents. The samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy(XPS), scanning electron microscopy(SEM), transmission electron microscopy and High-resolution transmission electron microscopy (TEM & HRTEM). It indicates that the manganese element was successfully incorporated into the anatase TiO2 nanostructure, and the atomic Mn-to-Ti could reach up to 18.2%. We also analyzed the merits and weaknesses of the nanostructured TMO in electrochemistry by dint of some relevant measures. And the cause of influence on the TMO electrochemical properties was briefly discussed.

Unusual facet and co-catalyst effects in TiO2-based photocatalytic coupling of methane

Photocatalytic coupling of methane to ethane and ethylene (C2 compounds) offers a promising approach to utilizing the abundant methane resource. However, the state-of-the-art photocatalysts usually suffer from very limited C2 formation rates. Here, we report our discovery that the anatase TiO2 nanocrystals mainly exposing {101} facets, which are generally considered less active in photocatalysis, demonstrate surprisingly better performances than those exposing the high-energy {001} facet. The palladium co-catalyst plays a pivotal role and the Pd2+ site on co-catalyst accounts for the selective C2 formation. We unveil that the anatase {101} facet favors the formation of hydroxyl radicals in aqueous phase near the surface, where they activate methane molecules into methyl radicals, and the Pd2+ site participates in facilitating the adsorption and coupling of methyl radicals. This work provides a strategy to design efficient nanocatalysts for selective photocatalytic methane coupling by reaction-space separation to optimize heterogeneous-homogeneous reactions at solid-liquid interfaces.

Templated Growth of In2S3 in Ti3C2TX MXene with Enhanced Photocatalytic Properties

The growth of ultrathin semiconductors is advantageous for photocatalysis due to improved photophysical properties and reduced charge recombination. Along these lines, templating the growth of semiconductors in confined spaces can allow control over semiconductor growth while also conferring the properties of the template to provide composite nanomaterial hybrids. Herein, the semiconductor In2S3 is grown in the organically‐modified interlayer space of Ti3C2TX MXene, a versatile 2D material with metallic character and broadband light absorption. The growth of 1–2 nm thick layers of In2S3 in the interlayer of MXene leads to a drastic increase in photocatalytic properties and light‐induced charge generation due to decreased interfacial charge transfer resistance. Interestingly, the hydrothermal conditions of In2S3 growth lead to partial oxidation of Ti3C2TX MXene to form anatase TiO2 nanocrystals, although this effect is strongly limited by increased In2S3 precursors due to passivation of the MXene surface. MXenes serve as effective templates for the confined growth of semiconductors, emphasizing the potential of MXene as a template for 2D material heterostructures. Overall, this work further develops MXene‐based 2D material composites, offering insights into the origins of the enhanced photocatalytic and photoelectrochemical properties, toward improvements in energy production and aqueous phase catalysis.

The electrochemical performances of high surface area mesocellular anatase TiO2 foam anode for lithium–ion battery

Porous anatase TiO2 with mesocellular foam structure (MCF−TiO2) was facilely prepared through hard-templating using mesocellular foam carbon (MCF−C), which had been prepared through hard-templating using mesocellular silica foam (MCF). During the dual hard-templating processes, the MCF−TiO2 well preserved the original three-dimensional (3D) mesocellular nanostructure of MCF. The wall of MCF−TiO2 was composed of very tiny anatase TiO2 nanocrystals (NCs). The TiO2 NCs were of less than 20 nm dimension. The surface area of MCF−TiO2 was 144 m2 g−1, and the MCF−TiO2 also contained large void spaces. The high surface area 3D nanostructured anatase MCF−TiO2 with large void spaces was ideal for Li+ transport and charge transfer reactions when MCF−TiO2 was applied to the anode material of the lithium–ion battery (LIB). Galvanostatic charge–discharge measurement and cyclic voltammetry confirmed that the MCF−TiO2 was an efficient anode material. The specific capacity after 50 cycles at a current rate of 0.1C reached 187 mAh g−1; it also showed stable recycling performances due to the robust high surface area 3D nanostructure.

Synthesis and growth mechanism of starfish-like anatase TiO2 nanocrystal with outstanding antibacterial property and super-hydrophobicity

Synthesis and growth mechanism of starfish-like anatase TiO2 nanocrystal with outstanding antibacterial property and super-hydrophobicity

Distinguishing the roles of anatase TiO2 nanocrystals with {101}, {010} or {001} facets catalyzed O3/H2O2 for low-temperature NO oxidation

To study the crystal facets effects of TiO2 on catalytic O3/H2O2 for NO oxidation at low temperature, anatase TiO2 nanocrystals with a high percentage of {101}, {010} and {001} facets were prepared by hydrothermal routes without fluorine. The percentages of the {101}, {010} and {001} facets in these three samples were 80%, 70% and 66%, respectively. The sequence of NO oxidation efficiency was determined as TiO2(001) (92%) > TiO2(101) (86%) > TiO2(010) (71%) under the molar ratio of O3/NO = 0.5 and H2O2/NO = 2.9. The crystal facets mechanism exhibited that TiO2(010) sample had the strongest Lewis acid sites, but TiO2(010) activated H2O2 to produce a stable Ti-OOH, which could not react with O3 to generate more •O2– radicals. TiO2(101) possessed a lower density of five-coordinated Ti atoms (Ti5c) than TiO2(010) and TiO2(001), the cooperative effect between Ti5c and H2O2 was the weakest. On the contrary, Ti-OOH on the surface of TiO2(001) was more active for •O2– production, meanwhile, TiO2(001) also exhibited the strongest NO adsorption properties. Thus, TiO2(001) had excellent NO oxidation efficiency.

Formation and growth of anatase TiO2 nanocrystals under hydrothermal conditions

This work is devoted to the study of the processes of formation and growth of TiO2 nanoparticles under hydrothermal conditions. TiO2 nanocrystals were obtained during the dehydration of hydrated titanium dioxide by varying the temperature and duration of hydrothermal treatment, as well as the method of precipitation of the synthesis precursor. The study of various characteristics of the synthesized TiO2 nanoparticles by PXRD, SEM, TEM, and low-temperature nitrogen sorption made it possible to propose mechanisms for the formation of crystalline titanium dioxide from an X-ray amorphous precursor and the growth of titanium dioxide nanocrystals with an anatase structure under hydrothermal conditions. Within the scope of the chosen model of oriented attachment, the dependence of the sizes of TiO2 crystallites on the parameters of hydrothermal synthesis is mathematically described. It was concluded that the direct precipitation of the synthesis precursor from titanium tetrachloride is superior to the reverse. It is shown that the temperature of hydrothermal treatment largely determines the size and morphology of the formed crystallites and TiO2 nanoparticles, the rate of the crystallization process, and the preferred mechanisms of nanocrystal growth, while the duration of synthesis affects the agglomeration processes and the specific surface area of titanium dioxide powders.

Charge Separation in BaTiO3 Nanocrystals: Spontaneous Polarization Versus Point Defect Chemistry.

The fate of photogenerated charges within ferroelectric metal oxides is key for photocatalytic applications. The authors study the contributions of i) tetragonal distortion, responsible for spontaneous polarization, and ii) point defects, on charge separation and recombination within BaTiO3 (BTO) nanocrystals of cubic and tetragonal structure. Electron paramagnetic resonance (EPR) in combination with O2 photoadsorption experiments show that BTO nanocrystals annealed at 600 °C have a charge separation yield enhanced by a factor > 10 compared to TiO2 anatase nanocrystals of similar geometries. This demonstrates for the first time the beneficial effect of the BTO perovskite nanocrystal lattice on charge separation. Strikingly, charge separation is considerably hindered within BTO nanoparticles annealed ≥ 600 °C, due to the formation of Ba-O divacancies that act as charge recombination centers. The opposing interplay between tetragonal distortion and annealing-induced defect formation inside the lattice highlights the importance of defect engineering within perovskite nanoparticles.

Water effect on the band edges of anatase TiO2 surfaces: A theoretical study on charge migration across surface heterojunctions and facet-dependent photoactivity.

The charge migration mechanism across the surface heterojunction constructed on an anatase TiO2 nanocrystal is still under debate. To solve this longstanding question, we present a systematic study of the band edges (vs. standard hydrogen electrode, SHE) of aqueous TiO2 interfaces with anatase (101), (100) and (001) surfaces, using a combination of density functional theory-based molecular dynamics (DFTMD) and efficient computational SHE (cSHE) methods. Our calculations show that the conduction band minimum (CBM) of the (101) surface is lower than that of (001) and (100) surfaces, which is thermodynamically favorable for electrons migrating to the (101) surface through the surface heterojunction, while the hole preferentially accumulates on the (100) surface due to its highest valence band minimum (VBM). In addition, we qualitatively explore the facet-dependent photocatalytic activity of anatase TiO2. Due to the possession of both the beneficial atomic structure (with 100% undercoordinated Ti5c atoms at the surface) and electronic structure (more strongly oxidizing holes in the VBM and efficient electron-hole spatial separation separation), the (001) surface exhibits the most efficient photocatalytic performance for water oxidation. Furthermore, it is confirmed that the use of simplified theoretical models neglecting the detailed atomic structures of water at the aqueous interface is inadequate to predict the band alignment of semiconductors relative to water redox potentials, so that it may result in substantial errors in evaluating the photocatalytic performance of materials to be used for water splitting.

Synthesis of High-Energy Faceted TiO2 Nanocrystals with Enhanced Photocatalytic Performance for the Removal of Methyl Orange

In this work, brookite TiO2 nanocrystals with co-exposed {001} and {120} facets (pH0.5-T500-TiO2 and pH11.5-T500-TiO2), rutile TiO2 nanorod with exposed {110} facets and anatase TiO2 nanocrystals with exposed {101} facets (pH3.5-T500-TiO2) and {101}/{010} facets (pH5.5-T500-TiO2, pH7.5-T500-TiO2 and pH9.5-T500-TiO2) were successfully synthesized through a one-pot solvothermal method by using titanium (V) iso-propoxide (TTIP) colloidal solution as the precursor. The crystal structure, morphology, specific surface area, surface chemical states and photoelectric properties of the pHx-T500-TiO2 (x = 0.5, 1.5, 3.5, 5.5, 7.5, 9.5, 11.5) were characterized by powder X-ray diffraction (XRD), field scanning transmission electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), nitrogen adsorption instrument, X-ray photoelectron spectroscopy (XPS), UV-Visible diffuse reflectance spectra and electrochemical impedance spectroscopy (EIS). The photocatalytic activity performance of the pHx-T500-TiO2 samples was also investigated. The results showed that as-prepared pH3.5-T500-TiO2 nanocrystal with exposed {101} facets exhibited the highest photocatalytic activity (95.75%) in the process of photocatalytic degradation of methyl orange (MO), which was 1.1, 1.2, 1.2, 1.3, 1.4, 1.6, 10.7, 15.1 and 27.8 fold higher than that of pH5.5-T500-TiO2 (89.47%), P25-TiO2 (81.16%), pH9.5-T500-TiO2 (79.41%), pH7.5-T500-TiO2 (73.53%), pH0.5-T500-TiO2 (69.10%), CM-TiO2 (61.09%), pH11.5-T500-TiO2 (8.99%), pH1.5-T500-TiO2 (6.33%) and the Blank (3.44%) sample, respectively. The highest photocatalytic activity of pH3.5-T500-TiO2 could be attributed to the synergistic effects of its anatase phase structure, the smallest particle size, the largest specific surface area and exposed {101} facets.

Plasmonic colloidal Nb-doped TiO2 nanocrystals with improved electrochromism in visible-infrared region

Dual-band electrochromic materials can achieve separate modulate of visible and near-infrared (NIR) transmittance, which are important components of smart windows. A promising colloidal Nb-doped TiO2 anatase nanocrystals (NCs) was prepared via the fluoride-assisted synthesis technique. The dual-band electrochromic properties of the NCs are closely related to the localized surface plasmon resonance (LSPR) absorption intensity. With the assistance of fluoride anions, TiO2 NCs can be easily doped with Nb, which is an important discovery. The product is a highly uniform Nb-doped TiO2 colloidal solution. Spectral analysis clarified that the Nb5+ replaced Ti4+, resulting in free carrier generation in the TiO2 conduction band, thereby exciting LSPR. Moreover, Nb-doped TiO2 NCs exhibited outstanding dual-band electrochromic properties including a wide modulation range for visible and NIR region (92.8 % at 620 nm and 75.2 % at 1800 nm) and a high electrochemical cycling stability (83.1 % at 620 nm and 70.3 % at 1800 nm after 1800 cycles). As a novel kind of electrochromic materials, the Nb-doped TiO2 NCs have great potential application for the smart windows.

Molecular oxygen enhances H2O2 utilization for the photocatalytic conversion of methane to liquid-phase oxygenates

H2O2 is widely used as an oxidant for photocatalytic methane conversion to value-added chemicals over oxide-based photocatalysts under mild conditions, but suffers from low utilization efficiencies. Herein, we report that O2 is an efficient molecular additive to enhance the utilization efficiency of H2O2 by suppressing H2O2 adsorption on oxides and consequent photogenerated holes-mediated H2O2 dissociation into O2. In photocatalytic methane conversion over an anatase TiO2 nanocrystals predominantly enclosed by the {001} facets (denoted as TiO2{001})-C3N4 composite photocatalyst at room temperature and ambient pressure, O2 additive significantly enhances the utilization efficiency of H2O2 up to 93.3%, giving formic acid and liquid-phase oxygenates selectivities respectively of 69.8% and 97% and a formic acid yield of 486 μmolHCOOH·gcatalyst−1·h−1. Efficient charge separation within TiO2{001}-C3N4 heterojunctions, photogenerated holes-mediated activation of CH4 into ·CH3 radicals on TiO2{001} and photogenerated electrons-mediated activation of H2O2 into ·OOH radicals on C3N4, and preferential dissociative adsorption of methanol on TiO2{001} are responsible for the active and selective photocatalytic conversion of methane to formic acid over TiO2{001}-C3N4 composite photocatalyst.

Facile Synthesis of TiO2/MoS2 Composites with Co-Exposed High-Energy Facets for Enhanced Photocatalytic Performance.

In this work, with the the H2TiO3 colloidal suspension and MoS2 as the precursors, TiO2/MoS2 composites composed of anatase TiO2 nanocrystals with co-exposed {101} and [111]-facets (nanorod and nanocuboid), {101} and {010} facets (nanospindle), and MoS2 microspheres constructed by layer-by-layer self-assembly of nanosheets were hydrothermally synthesized under different pH conditions. The characterization has been performed by combining X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectra, and UV-visible absorption spectrum analyses. The photocatalytic degradation of rhodamine B (RhB) in an aqueous suspension was employed to evaluate the photocatalytic activity of the as-prepared pHx-TiO2/MoS2 composites. The photocatalytic degradation efficiency of pH3.5-TiO2/MoS2 composite was the highest (99.70%), which was 11.24, 2.98, 1.48, 1.21, 1.09, 1.03, 1.10, and 1.14 times that of Blank, MoS2, CM-TiO2, pH1.5-TiO2/MoS2, pH5.5-TiO2/MoS2, pH7.5-TiO2/MoS2, pH9.5-TiO2/MoS2, pH11.5-TiO2/MoS2, respectively. The pH3.5-TiO2/MoS2 composite exhibited the highest photocatalytic degradation rate, which may be attributed to the synergistic effects of its large specific surface area, suitable heterojunction structure, and favorable photogenerated charge-separation efficiency. This work is expect to provide primary insights into the photocatalytic effect of TiO2/MoS2 composite with co-exposed high-energy facets, and make a contribution to designing more efficient and stable photocatalysts.

Determination of Crystallographic Orientation and Exposed Facets of Titanium Oxide Nanocrystals.

Titanium dioxide (TiO2 ) nanocrystals have attracted great attention in heterogeneous photocatalysis and photoelectricity fields for decades. However, contradicting conclusions on the crystallographic orientation and exposed facets of TiO2 nanocrystals frequently appear in the literature. Herein, using anatase TiO2 nanocrystals with highly exposed {001} facets as a model, the misleading conclusions that exist on anatase nanocrystals are clarified. Although TiO2 -001 nanocrystals are recognized to be dominated by {001} facets, in fact, anatase nanocrystals with both dominant {001} and {111} facets always co-exist due to the similarities in the lattice fringes and intersection angles between the two types of facets (0.38nm and 90° in the [001] direction, 0.35nm and 82° in the [111] direction). A paradigm for determining the crystallographic orientation and exposed facets based on transmission electron microscopy (TEM) analysis, which provides a universal methodology to nanomaterials for determining the orientation and exposed facets, is also given.

Scavenger-Supported Photocatalytic Evidence of an Extended Type I Electronic Structure of the TiO2@Fe2O3 Interface.

Heterostructures of TiO2@Fe2O3 with a specific electronic structure and morphology enable us to control the interfacial charge transport necessary for their efficient photocatalytic performance. In spite of the extensive research, there still remains a profound ambiguity as far as the band alignment at the interface of TiO2@Fe2O3 is concerned. In this work, the extended type I heterojunction between anatase TiO2 nanocrystals and α-Fe2O3 hematite nanograins is proposed. Experimental evidence supporting this conclusion is based on direct measurements such as optical spectroscopy, X-ray photoemission spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), and the results of indirect studies of photocatalytic decomposition of rhodamine B (RhB) with selected scavengers of various active species of OH•, h•, e–, and •O2–. The presence of small 6–8 nm Fe2O3 crystallites at the surface of TiO2 has been confirmed in HRTEM images. Irregular 15–50 nm needle-like hematite grains could be observed in scanning electron micrographs. Substitutional incorporation of Fe3+ ions into the TiO2 crystal lattice is predicted by a 0.16% decrease in lattice parameter a and a 0.08% change of c, as well as by a shift of the Raman Eg(1) peak from 143 cm–1 in pure TiO2 to 149 cm–1 in Fe2O3-modified TiO2. Analysis of O 1s XPS spectra corroborates this conclusion, indicating the formation of oxygen vacancies at the surface of titanium(IV) oxide. The presence of the Fe3+ impurity level in the forbidden band gap of TiO2 is revealed by the 2.80 eV optical transition. The size effect is responsible for the absorption feature appearing at 2.48 eV. Increased photocatalytic activity within the visible range suggests that the electron transfer involves high energy levels of Fe2O3. Well-programed experiments with scavengers allow us to eliminate the less probable mechanisms of RhB photodecomposition and propose a band diagram of the TiO2@Fe2O3 heterojunction.

Tailoring Ir-FeOx interactions and catalytic performance in preferential oxidation of CO in H2 via the morphology engineering of anatase TiO2 over Ir-FeOx/TiO2 catalysts

Ir-FeOx/TiO2 catalysts with both Ir and Fe contents of ∼1% wt. employing anatase TiO2 nanocrystals predominantly exposing either {100}, {101}, or {001} facets as the support were prepared and a comprehensive study was conducted on their interactions in pairs that are strongly dependent on the TiO2 morphology. The strongest FeOx-TiO2 interactions occurred over TiO2{001} support while TiO2{101} support contributes to the strongest Ir-TiO2 and Ir-FeOx interactions. Catalytic performance of the Ir-FeOx/TiO2 catalysts in preferential oxidation of CO in H2 is not only affected by the CO reactivity, but also determined by the Ir-FeOx interfaces. Ir-FeOx/TiO2{101} catalyst exhibits the highest CO conversion and best O2 selectivity over the three Ir-FeOx/TiO2 catalysts, which could be ascribed to stronger Ir-FeOx interactions that contribute to the enhancement of a H-spillover effect and subsequently facilitate the transformation of surface carbonaceous intermediates into CO2. These results add the versatility of the morphology engineering strategy in tailoring the structures and catalytic performance of oxide-based catalysts, and broaden the concept of morphology-dependent catalysis of oxide-based nanocrystal catalysts.

Graphene-assisted titanium dioxide Z-mechanism photoelectrode as enzymatic glucose biosensor

Highly exposed surfaces of anatase TiO2 crystals are of interest due to their excellent photogenerated electron–hole pair separation effect and high photocatalytic activity. In this work, a Z-mechanism biosensor with reduced graphene oxide (rGO) and anatase TiO2 nanocrystals combined with PDA (TiO2/rGO/PDA) was successfully synthesized. rGO was combined with the co-exposed (001) and (101) facets of TiO2 nanocrystals to construct a Z-mechanism in which rGO acts as an electron transport medium and provides a channel for the transfer of electrons, resulting in TiO2 nanocrystals with high photoelectron–hole pair separation efficiency and strong redox ability. The coated PDA polymer not only could absorb visible light but also has good stability and biocompatibility, which helps to increase the adsorption of target enzyme molecules. The TiO2/rGO/PDA/GOx biosensor with the Z-mechanism displays the sensitivity of 13.82 μA mM−1 cm−2 in 0.1M PBS solution (pH = 7.4) with a linear range of 0–3 mM and the LOD of 0.034 µM. In general, the application of the Z-mechanism in biosensors would provide a new orientation for the design of biosensors.