Photoelectrochemical Electrode Research Articles

Boosting visible-light photoelectrochemical water splitting response of WO3–MoS2 nanocomposites by transition metal doping: Experimental and first-principles studies

The current study employs both theoretical and experimental methods to investigate the effect of Ti and Co doping on the WO3 nanocomposite with MoS2 photoanode's photoelectrochemical (PEC) water-splitting reaction. A simple hydrothermal and sol-gel method was adopted for the preparation of samples. The Ti-doped WO3–MoS2 (1.96 at %) sample showed the maximum optical absorption with a photocurrent density of 1.15 mA/cm2 at 1.6 V vs Ag/AgCl. The improvement in photocurrent density may be ascribed to the upward shifting of the conduction band edge towards the H+/H2 redox potential as well as the presence of a large number of active sites in MoS2. A high value of flat band potential of −0.3 V vs Ag/AgCl was achieved in Ti-doped WO3–MoS2, which was confirmed by Mott-Schottky measurements with the corresponding lowest charge transfer resistance at the semiconducting electrode/electrolyte interface. Furthermore, density functional theory calculations have also indicated that on doping WO3 with Ti and Co, there is a slight upward shift in the conduction band minimum, without any significant change in the valence band maximum, with respect to the Fermi level. This study provides new insight into the impact of transition metal doping and nanocomposite of chalcogenide materials for WO3-based PEC electrodes.

A Solar and Seawater Co‐Involved Durable Rechargeable Battery Enabled by Crown Ether‐Rich Polymer‐Mediated Photoelectrodes

AbstractThe first flow‐type solar and seawater co‐mediated sodium‐air rechargeable battery (SSRB) for efficient solar‐to‐electrochemical energy conversion/storage is established. Such SSRB is enabled by a robust self‐regulated CEP/ZnWO4/WO3 heterojunction photoelectrochemical electrodes (PE) by passivating predesigned crown ether‐rich photoresponsive covalent organic polymer (CEP) layers onto ZnWO4‐modified WO3 nanosheet arrays. The PE design utilizes the previously‐unexplored self‐mediated effect of CEP to endow PE with superior stability, facilitated electrode reaction kinetics, and high efficiency of spatial charge separation simultaneously. This leads to remarkable light‐enhanced oxygen evolution catalysis with impressive photocurrent density up to 6.1 mA cm−2 at 1.23 V versus RHE in seawater – surpassing metal‐oxide‐based PEs ever reported for seawater splitting. Thus, the SSRB breaks the limit of the equilibrium voltage (3.47 V) of conventional seawater sodium‐air cells to deliver a low charge voltage of 2.71 V along with stable photo‐charge over 100 h and good photo‐charge/normal discharge cycling stability over 240 h – superior to almost all existing light‐involved air batteries. Combined experimental and modeling studies for the first time unveil the multi‐regulation effects of CEP passivation which prevents detrimental Cl‐corrosion, and promote oxygen evolution kinetics.

Cu2O/ZnFe2O4 nanorod photoelectrode for photoelectrochemical water splitting

Photoelectrochemical water splitting is a promising technology for H2 generation via water splitting reaction using the semiconductor material. In this research, the ZnFe2O4/Cu2O nanorod was investigated. The products were synthesized by the electrochemical deposition method. The characteristics of materials were investigated by X-ray diffraction, scanning electron microscopy, and UV-visible spectroscopy. All materials exhibited the ptype photoelectrode characteristic. The performance of photoelectrochemical electrodes was studied by linear swept voltammetry, electrochemical impedance spectroscopy, and Mott-Schottky analysis. The best condition deposition was by applying -0.4 V and 10 min. The highest photocurrent density was 0.8 mA.cm-2 at -0.5 (vs. Ag/AgCl) bias voltage.

Facile synthesis of CoOx@C/Ti-Fe2O3 photoanodes for efficient photoelectrochemical water oxidation.

The development of photoelectrochemical (PEC) water splitting is hindered by the slow kinetics of four-electron processes for the oxygen evolution reaction (OER) and severe charge recombination. Amorphous carbon was chosen as a carrier for the active sites due to its exceptional conductivity and strong loading capacity. In addition, this enhanced performance was attributed to the loading of oxides of cobalt. Here, amorphous carbon-covered cobalt oxides chosen as a co-catalyst loaded on α-Fe2O3 (noted as CoOx@C/Ti-Fe2O3) have been synthesized, and they show a high current density (2.86 mA cm-2 under 1.23 V vs. RHE), and a low onset potential (0.611 V vs. RHE). Experimental analysis demonstrates that the charge transfer and separation leading to accelerated OER dynamics and improved PEC performance are enhanced by CoOx@C effectively. This study provides new ideas for designing high-performance photoelectrochemical electrodes based on amorphous carbon co-catalysts.

3D/1D heterostructure of p-BiOBr nanoflowers modified n-TiO2 nanorod arrays for highly sensitive photoelectrochemical determination of hydrogen peroxide

Hydrogen peroxide (H2O2) is a major transmitter of redox signals during chemical processes. Cost-effective and easy-to-operate sensors for H2O2 are in high demand in a variety of fields. A novel photoelectrochemical (PEC) sensor for H2O2 detection was investigated, using BiOBr/TiO2NAs/FTO (BiOBr/TNAs) as a PEC electrode which is obtained by successive ionic layer adsorption and reaction (SILAR) method. This non-enzymatic PEC BiOBr/TNAs electrode shows excellent selectivity, stability, and reproducibility for H2O2 detection in optimizing modes. The linear relationship is in a broad range from 4 to 1800 μM (R2 = 0.994) and a detection limit of 0.65 μM (S/N = 3). In the detection of H2O2 in apple juice and milk real samples, the BiOBr/TNAs show outstanding recovery ranging from 98.0 % to 102.0 %, indicating great potential in practical applications. Meanwhile, the p-n heterojunction formed between BiOBr and TiO2 improves the utilization of visible light and effectively promotes the separation of photogenerated electrons and holes. This work provides a new strategy for the non-enzymatic detection of hydrogen peroxide in PEC mode.

Improved Sensitivity and Selectivity of Glutathione Detection through Target-Driven Electron Donor Generation in Photoelectrochemical Electrodes.

Glutathione (GSH) plays a vital role in many physiological processes, and its abnormal levels have been found to be associated with several diseases. In contrast to traditional methods using electron donor-containing electrolytes for photoelectrochemical (PEC) sensing, in this study, a target-driven electron donor generation in a PEC electrode was developed to detect GSH. Using well-aligned TiO2 nanotube arrays (TNTs) as the PEC substrate, mesoporous MIL-125(Ti) was grown in the TNTs through an in situ solvothermal method and subsequent two-step annealing treatment. The accommodation capacity of mesoporous MIL-125(Ti) allows a well loading of cystine and Pt nanoclusters (NCs). Taking advantage of the specific cleavage ability of disulfide bonds by GSH, cystine was converted to cysteine, which served as the electron donor for the PEC process. Benefiting from the confinement effect of mesoporous MIL-125(Ti), cysteine was effectively oxidized to cysteine sulfinic acid by the photogenerated holes. Importantly, the highly active Pt NCs decorated in the mesopores not only improved the charge transfer but also accelerated the above oxidation reaction. The synergistic effect of these factors enabled the efficient separation of the photogenerated electron-hole pairs, which induced a significant photocurrent increase and in turn led to the high-sensitivity detection of GSH. Consequently, the proposed PEC biosensor exhibited excellent performance in the detection of GSH in serum specimens. The target-driven electron donor generation designed in this study might open a new route for developing sensitive and selective PEC biosensors with application in complex biological environments.

Insight into interface electronic structure of ZnIn2S4/TiO2 heterostructure for enhanced photoelectrochemical glycerol oxidation

Developing a high-efficiency photoelectrochemical (PEC) electrode for the glycerol oxidation reaction (GOR) is important for producing valuable products. The PEC performance could be enhanced by rationally designing heterostructures with inhibited recombination of charge carriers. Nevertheless, the interface electronic structure of heterostructures has not been comprehensively analyzed. In this work, the PEC GOR performance of ZnIn2S4/TiO2 heterostructure photoanode showed 1.7 folds enhancement than that of pure TiO2 photoanode at 1.23 V vs. RHE. The ZnIn2S4/TiO2 heterostructure was simulated by constructing ZnIn2S4 on the TiO2 single crystal, which was beneficial for investigating the interface electronic structure of heterostructure. Single-particle spectroscopy demonstrated a significantly increased lifetime of charge carriers. Combined with the in-situ X-ray photoelectron spectroscopy, Kelvin probe force microscopy, work function, and electron paramagnetic resonance, the interface electronic structure of the ZnIn2S4/TiO2 heterostructure was proposed with a Z-scheme mechanism. This work provides a comprehensive strategy for analyzing the interface electronic structure of heterostructures.

Photoelectrochemical Deposition of Silicon–Carbon Layer on P-Type Semiconductors and Aluminum–Copper Alloy in Ionic Liquid

Electrochemical deposition of silicon at room temperature is problematic due to the intrinsically low conductivity of the deposits. This study reports the photoelectrochemical (PEC) deposition of silicon (Si) and silicon–carbon (Si–C) layers from an ionic liquid at 40 °C using silicon tetrachloride (SiCl4) as a silicon precursor. Amorphous layers are deposited on p-type silicon (p-Si), p-type gallium arsenide (p-GaAs), and aluminum–copper alloy AA2024. The semiconductor substrates are activated by white LED illumination, which generates photoelectrons, thereby making the substrate conductive with respect to the cathodic reaction. The photoresponsiveness of the deposits is proven by the light-induced photocurrents on an optically inactive substrate made of the alloy AA 2024. The proposed method paves the way for the electrochemical modification of semiconductors and metals with Si and Si–C structures, which are applicable in various fields, such as batteries, anti-corrosion coatings, photovoltaics, or PEC electrodes for hydrogen production.

Coupled Solar Battery with 6.9 % Efficiency.

Solar-to-electrochemical energy storage in solar batteries is an important solar utilization technology comparable to solar-to-electricity (solar cells) and solar-to-fuel (photocatalytic cells) conversion. Unlike the indirect approach of integrated solar flow batteries combining photoelectrodes with redox-electrodes, coupled solar batteries enable direct solar energy storage, but are hampered by low efficiency due to rapid charge recombination of materials and misaligned energy levels between electrodes. Herein, we propose a design for a coupled solar battery that intercouples two photo-coupled ion transfer (PCIT) reactions through electron-ion transfer upon co-photo-pumping of photoelectrochemical storage cathode and anode. We used a representative covalent organic framework (COF) to achieve efficient charge separation and directional charge transfer between two band-matched photoelectrochemical storage electrodes, with a photovoltage sufficient for COF dual-redox reactions. By pumping these electrodes, the coupled solar battery stores solar energy via two synergistic PCIT reactions of electron-proton-relayed COF oxidation and reduction, and the stored solar energy is released as electrochemical energy during COF regeneration in discharge while interlocking the loops. A breakthrough in efficiency (6.9 %) was achieved, adaptive to a large-area (56 cm2 ) tandem device. The presented photo-intercoupled electron-ion transfer (PIEIT) mechanism provides expandable paths toward practical solar-to-electrochemical energy storage.

Coupled Solar Battery with 6.9 % Efficiency

AbstractSolar‐to‐electrochemical energy storage in solar batteries is an important solar utilization technology comparable to solar‐to‐electricity (solar cells) and solar‐to‐fuel (photocatalytic cells) conversion. Unlike the indirect approach of integrated solar flow batteries combining photoelectrodes with redox‐electrodes, coupled solar batteries enable direct solar energy storage, but are hampered by low efficiency due to rapid charge recombination of materials and misaligned energy levels between electrodes. Herein, we propose a design for a coupled solar battery that intercouples two photo‐coupled ion transfer (PCIT) reactions through electron‐ion transfer upon co‐photo‐pumping of photoelectrochemical storage cathode and anode. We used a representative covalent organic framework (COF) to achieve efficient charge separation and directional charge transfer between two band‐matched photoelectrochemical storage electrodes, with a photovoltage sufficient for COF dual‐redox reactions. By pumping these electrodes, the coupled solar battery stores solar energy via two synergistic PCIT reactions of electron‐proton‐relayed COF oxidation and reduction, and the stored solar energy is released as electrochemical energy during COF regeneration in discharge while interlocking the loops. A breakthrough in efficiency (6.9 %) was achieved, adaptive to a large‐area (56 cm2) tandem device. The presented photo‐intercoupled electron‐ion transfer (PIEIT) mechanism provides expandable paths toward practical solar‐to‐electrochemical energy storage.

The electrochemical performance of Lanthanum Indium Sulphide photoactive electrode in a simple yet efficacious photoelectrochemical cell

The most effective way to boost electrochemical efficiency is to design nanostructures that fully exploit the advantages of all metals and create an interfacial impact between structures. In this study, diethyl dithiocarbamate compound is used to produce an elongated with flowery flakes In:SnO2/La3InS6 structure. The morphological, crystalline, and opto-electrical properties of the substance were examined. According to UV–visible analysis, the direct optical band gap was 4.2 eV. The core level of La3d, In3d and S2p was revealed by X-ray photoelectron spectroscopy. Electrical testing of a photoelectrochemical cell's transparent photoactive electrode revealed an extraordinary specific capacity of 603 F g-1 at 5 mV s−1 when illuminated. The photoelectrode's brief chronoamperometric response showed the creation of 19.8 mA of photocurrent. In the presence of light, higher photocurrent densities were obtained at each scan rate, demonstrating that exposure to light enhanced the performance of the electrode. A helpful photoelectrode that may be applied to renewable energy systems is unquestionably introduced by this work.

Solar photoelectro-Fenton: A very effective and cost-efficient electrochemical advanced oxidation process for the removal of organic pollutants from synthetic and real wastewaters

Recalcitrant and toxic organic pollutants from wastewaters are scarcely removed in conventional wastewater treatment plants. To preserve the water quality, organics need to be removed by developing powerful oxidation technologies. Our laboratory proposed in 2007 a potent electrochemical advanced oxidation process (EAOP) for wastewater remediation, so-called solar photoelectro-Fenton (SPEF). This review summarizes the advances of this emerging technology up to 2022, making evident its effectiveness and cost-efficiency for the destruction of usual organic pollutants. The simultaneous action of generated hydroxyl radicals and the photolysis by sunlight explains the high oxidation power of SPEF respect to other EAOPs. The review is initiated by describing the fundamentals of the process to remark the role of the produced oxidants and the benefits of using solar irradiation in its performance. The photoelectrochemical systems used (bench tank reactor and solar pre-pilot flow plant) and the assessment of the operating variables are discussed. The characteristics of the most common homogeneous SPEF for the degradation and mineralization of several synthetic solutions of industrial chemicals, herbicides, pharmaceuticals, and synthetic organic dyes, as well as of some real wastewaters, are further described. The influence of the photoelectrochemical cell, electrodes, solution pH, electrolyte composition, Fe2+ and pollutant concentration, and current density is analyzed. The performance of a homogeneous SPEF-like process with active chlorine and heterogeneous SPEF processes with solid catalysts such as Fe3O4 and sodium vermiculite is also discussed. Finally, the advances of homogeneous SPEF combined with other techniques like solar photocatalysis, solar photoelectrocatalysis, anaerobic digestion, and nanofiltration are reported.

Promoting photoelectrochemical water oxidation of BiVO4 photoanode via Co-MOF-derived heterostructural cocatalyst

The sluggish surface reaction kinetic is the bottleneck limiting the photoelectrochemical (PEC) water oxidation of BiVO4 photoanode, especially for the porous structured BiVO4 with high surface area. Here, Co-based metal–organic frameworks (MOFs) were modified on porous BiVO4 photoanode followed by calcining in the N2 atmosphere, forming BiVO4-MOF-N2 photoanode. The MOF-derived heterostructural cocatalysts significantly enhanced the photocurrent density of BiVO4-MOF-N2, reaching 2.32 mA·cm−2 (1.23 V vs RHE), about 1.15 times that of BiVO4-MOF and 2.64 times that of pristine BiVO4. The comparative study of BiVO4-MOF-N2, BiVO4-MOF, and pristine BiVO4 photoanodes suggested that the Co-MOF-derived heterostructural cocatalyst had a much stronger effect on promoting the surface reactions than pure MOF. The BiVO4-MOF-N2 photoanode had the highest charge transfer efficiency of 63.1 % at 1.3 V vs RHE and the lowest charge transfer resistivity compared with BiVO4 and BiVO4-MOF. Both Co-active centers and conductive carbon matrix contributed to the enhanced charge transfer of BiVO4-MOF-N2 photoanode. A MOF-loading-time dependent PEC performance of BiVO4 photoanode also indicated that the intermediate charge transfer process from BiVO4 to active centers strongly affected the final charge transfer and PEC performances. This work provides new insights into the design of high-performance photoelectrochemical electrodes based on heterostructural cocatalysts.

TiO2 nanotube arrays as a photoelctrochemical platform for sensitive Ag+ ion detection based on a chemical replacement reaction

Silver ions (Ag+) are essential for living organisms; however, they are toxic at high concentrations. Herein, a photoelectrochemical (PEC) platform is constructed using TiO2 nanotube arrays (TiNTs) prepared by electrochemical anodization of electrode substrate, with high photocurrent response in visible-light region by coating PbS nanocrystals (NCs) through continuous chemical bath deposition (CBD) technique. Combining the low band-gap of PbS with the improved photogenerated electron-hole separation at PbS/TiO2 heterojunctions, the resulting PbS/TiNTs electrode possesses a highly improved PEC response under visible light. Owing to an efficient chemical replacement of Pb(II) in PbS by targeted Ag+ ions, the formed Ag2S components become the new recombination centers for charge carriers, leading to decreased PEC response. Based on photocurrent reduction, the PEC electrode demonstrated an excellent sensing ability for trace Ag+ in solution with a linear range of 5.0 × 10−3 ∼ 5.0 × 10−8 mol L−1 and a limit of detection reaching 1.5 × 10−8 M (S/N = 3). The semiconductor hybrid nanotubes-based photoelectrochemical platform provides a promising route to design highly sensitive and selective sensors for directly detecting ions or molecules.

Kinetically versus thermodynamically controlled factors governing elementary pathways of GaP(111) surface oxidation

GaP and related III-V semiconductors have attracted interest as high-efficiency photoelectrochemical electrodes for solar water splitting. However, their efficacy is linked to the presence, identity, and integrity of native surface oxides, which are structurally and chemically complex and evolve during operation. Using ambient pressure X-ray photoelectron spectroscopy (APXPS) coupled with ab initio simulations, we track key chemical motifs expressed during evolution of GaP(111) surface oxides, their associated reaction kinetics, and their correlations with electronic properties. We identify two distinct thermal regimes corresponding to kinetically and thermodynamically controlled oxidation. Below 600 K, exposure to O2 generates kinetically facile Ga-O-Ga configurations, whereas higher temperatures cause activated oxygen to insert into Ga–P bonds as part of a thermodynamically driven transformation into a complex, heterogeneous 3D network of surface POx (1≤x ≤ 4) groups and Ga2O3 species, the latter of which eventually dominates upon depletion of surface phosphorus. Our study highlights the critical competition between kinetic and thermodynamic factors during GaP oxidation, yielding insights for fabricating stable III-P-based photoelectrodes with precisely engineered surface properties.

A carbon quantum layer modified BiVO4 photoelectrochemical aptamer biosensor for ultra-sensitive cTnI biomarker detection based on the interface nephelauxetic effect and heterojunction assistance.

The sensitivity and specificity of a semiconductor photoelectrochemical (PEC) aptamer biosensor are determined by the separation and transport of the photoinduced carriers as well as aptamer probe immobilization. In this study, an in situ thermal transformation organic polymer strategy was employed to produce an ∼2.5 nm carbon quantum layer on the surface of the BiVO4(BVO) photoanode. Experimental tests and theoretical calculations have revealed that this carbon quantum layer-coated BVO(C@BVO) heterostructure could generate surface charge depletion regions through an interface nephelauxetic effect. These charge depletion regions facilitated the efficient immobilization of DNA aptamer probes of the acute myocardial infarction biomarker cardiac troponin I (cTnI), while showing almost no immobilization capability on a pure-phase C quantum layer or BVO crystals. Simultaneously, the formation of the C@BVO heterostructure also enhanced the directional transport of photo-generated holes from BVO to the C quantum layer. Due to the above reasons, the C@BVO PEC aptamer biosensor achieved a linear detection range for cTnI from 10-14 g L-1 to 10-10 g L-1, with a record detection limit (LOD) of ∼0.33 × 10-14 g L-1 (N > 3). Meanwhile, the biosensor also demonstrated well the detection reproducibility and specificity for cTnI detection. Therefore, the strategy of using a carbon quantum layer-coated PEC electrode shows good potential to develop PEC biosensors with high sensitivity, specificity, and robustness.

Synthesis of photocatalytic TiO2 nanotubes on additively manufactured Ti-alloy substrates

The pursuit of sustainable and clean energy sources has led to the exploration of green hydrogen as a versatile and eco-friendly energy carrier. This research paper focuses on the application of photocatalytic electrolysis, particularly utilizing titanium dioxide (TiO2) nanotubes, for efficient hydrogen production. The study investigates the synthesis of TiO2 nanotubes on additive manufacturing (AM)-produced substrates and explores the effects of post-synthesis annealing and cleaning techniques. The results demonstrate well-organized and uniform nanotubes, with the morphology depending on the annealing ramp rate. X-ray diffraction analysis reveals a phase transformation to anatase with a grain size of approximately 28 nm upon annealing. The study emphasizes the importance of post-synthesis cleaning in achieving desired nanotube surfaces. Cleaning with ethanol followed by 10 vol% HCl produces well-organized nanotubes of varying sizes. Overall, the research contributes to the understanding of surface modification techniques and nanostructured architectures for optimizing hydrogen photoelectrodes. The study also highlights the potential of AM in advanced fabrication methods for improved photoelectrochemical electrodes and offers valuable insights for future work in this field.

A TiO2@MWCNTs nanocomposite photoanode for solar-driven water splitting.

A TiO2@MWCNTs (multi-wall carbon nanotubes) nanocomposite photoanode is prepared for photoelectrochemical water splitting in this study. The physical and photoelectrochemical properties of the photoanode are characterized using field emission-scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and linear sweep voltammetry. The results show that the TiO2@MWCNTs nanocomposite has an optical bandgap of 2.5 eV, which is a significant improvement in visible-light absorption capability compared to TiO2 (3.14 eV). The cyclic voltammograms show that incorporating TiO2 with the MWCNTs leads to a decrease in the electrical double layer, thereby facilitating the electron transfer rate in the TiO2@MWCNTs electrode. Moreover, the current density of the photoelectrochemical electrode formed by TiO2@MWCNTs under solar irradiation is significantly higher than that prepared by TiO2 (vs Ag/AgCl). The low charge capacity of the TiO2@MWCNTs electrode-electrolyte interface hinders the recombination of the photogenerated electrons and holes, which contributes to the enhancement of the solar-to-hydrogen (STH) conversion efficiency. The average STH conversion efficiency of the TiO2@MWCNTs electrode under solar exposure from 6 AM to 5 PM is 11.1%, 8.88 times higher than that of a TiO2 electrode. The findings suggested TiO2@MWCNTs is a feasible nanomaterial to fabricate the photoanode using photoelectrochemical water splitting under solar irradiation.

Thin Layers of SrTiO3-TiO2 with Eutectic Composition for Photoelectrochemical Water Splitting

Hydrogen as a potential fuel of the future can be produced in a photoelectrochemial water splitting process. Herein, we demonstrate the fabrication of photoelectrochemical electrodes based on SrTiO3-TiO2 with a eutectic composition on titanium and conductive glass FTO (fluorine doped tin oxide) substrates by magnetron sputtering. The XRD and SEM/EDS reveal the amorphous nature and homogeneity of the sputtered material. The influence of the layer thickness on the photoactivity was investigated. There were three-layer thicknesses (50, 350, and 750 nm) selected by sputtering for 12, 80 and 220 min for the preparation of photoelectrodes. The photoelectrochemical analysis confirms the photoactivity of the obtained layers under illumination with a xenon lamp (600 mW/cm2). The highest photocurrent density of 11.8 × 10−3 mAcm−2 at 1.2 V vs. SCE was recorded for a layer thickness of 50 nm on titanium as better matching between the Ti work function and the conduction band.

Heterostructure-based 3D-CdS/TiO2 nanotubes/Ti: Photoelectrochemical performances and interface simulation investigation

Heterojunction can effectively improve the charge separation efficiency and facilitate electron transfer, producing a strong photoelectric signal. By using 3D-TiO2 nanotubes/Ti foil as support, CdS–TiO2 heterojunction electrodes with different CdS proportions were fabricated as photoelectrochemical (PEC) biosensor to respond the visible irradiation and improve the PEC performance of TiO2 nanotubes. Density functional theory (DFT) simulation was conducted to clarify the PEC process of CdS–TiO2NTs and revealed the important role of CdS in enhancing electron–hole separation on TiO2 nanotubes. Owing to the 3D tubular structure of the support, 2 mM CdS–TiO2 nanotubes/Ti PEC electrode exhibited low detection limit of 0.27 μM and good sensitivity of 328.87 μA mM−1 cm−2 for glucose in the range of 2–9 μM under visible illumination. The fabricated CdS–TiO2 nanotubes/Ti biosensor also showed high selectivity and good stability, which indicated a new candidate for biosensors.