Bimetallic phosphide decorated Mo–BiVO4 for significantly improved photoelectrochemical activity and stability

Bismuth vanadate photoanode has shown great potential for photoelectrochemical (PEC) catalysis, but it needs to be further modified because of its relatively low charge-separation efficiency and poor stability. Herein, the bimetallic phosphide NiCoP decorated Mo–BiVO₄ is fabricated through the electrodeposition and drop-casting method, which significantly improves the charge separation and surface oxidation reaction. Therefore, the fabricated NiCoP/Mo–BiVO₄ photoanode exhibits a low onset potential of 0.21 V (vs. RHE) and high photocurrent of 3.21 mA cm⁻² at 1.23 V (vs. RHE), which is 3.12 times higher than that of pure BiVO₄. Importantly, the decoration of NiCoP significantly improve the stability of BiVO₄ photoanode.

Bimetallic phosphide NiCoP decorated Mo–BiVO₄ photoanode was fabricated, and showed significantly improved photoelectrochemical activity and stability.     

Green fabrication of nanoporous BiVO4 films on ITO substrates for photoelectrochemical water-oxidation

A new green method was developed to prepare nanoporous BiVO₄ films on ITO substrates for photoelectrochemical (PEC) water-oxidation under visible light irradiation. The films can be prepared by simple drop-casting of a stable aqueous solution of Bi³⁺ and V⁵⁺ complexes with tartaric acid and ethylenediaminetetraacetic acid, followed by drying and calcination in air. Thanks to these ligands, the aqueous precursor solution is remarkably stable over a wide range of pH (pH 4–9). The BiVO₄ films on ITO substrates possess a 3D-network structure comprised of nanoparticles with a scheelite–monoclinic phase and a diameter of ca. <100 nm, after calcination at 450–500 °C for 1 h. The PEC performance clearly depended on the film thickness that can be controlled by coating times, and calcination conditions (temperature and time). The CoPi-loaded BiVO₄ electrodes exhibited relatively high performance for PEC water oxidation (ABPE of 0.35% at 0.8 V vs. RHE) under simulated sunlight irradiation.

Nanoporous BiVO₄ photoanodes for efficient water oxidation were directly fabricated on an ITO substrate using an aqueous solution of mild pH.     

Efficient photoelectrochemical water oxidation using a TiO2 nanosphere-decorated BiVO4 heterojunction photoanode

Constructing heterojunctions by coupling dissimilar semiconductors is a promising approach to boost charge separation and charge transfer in photoelectrochemical (PEC) water splitting. In this work, we fabricated a highly efficient TiO₂/BiVO₄ heterojunction photoanode for PEC water oxidation via a simple hydrothermal method. The resulting heterojunction photoanodes show enhanced PEC performance compared to the bare BiVO₄ due to the simultaneous improvements in charge separation and charge transfer. Under simulated sunlight illumination (AM 1.5G, 100 mW cm⁻²), a high photocurrent of 3.3 mA cm⁻² was obtained at 1.23 V (vs. the reversible hydrogen electrode (RHE)) in a neutral solution, which exceeds those attained by the previously reported TiO₂/BiVO₄ heterojunctions. When a molecular Co–cubane catalyst was immobilized onto the electrode, the performance of the TiO₂/BiVO₄ heterojunction photoanode can be further improved, achieving a higher photocurrent density of 4.6 mA cm⁻² at 1.23 V, an almost three-fold enhancement over that of the bare BiVO₄. These results engender a promising route to designing an efficient photoelectrode for PEC water splitting.

Constructing heterojunctions by coupling dissimilar semiconductors is a promising approach to boost charge separation and charge transfer in photoelectrochemical (PEC) water splitting.     

Efficient charge separation and transfer of a TaON/BiVO4 heterojunction for photoelectrochemical water splitting

The separation and transfer of photogenerated electron–hole pairs in semiconductors is the key point for photoelectrochemical (PEC) water splitting. Here, an ideal TaON/BiVO₄ heterojunction electrode was fabricated via a simple hydrothermal method. As BiVO₄ and TaON were in well contact with each other, high performance TaON/BiVO₄ heterojunction photoanodes were constructed. The photocurrent of the 2-TaON/BiVO₄ electrode reached 2.6 mA cm⁻² at 1.23 V vs. RHE, which is 1.75 times as that of the bare BiVO₄. TaON improves the PEC performance by simultaneously promoting the photo-generated charge separation and surface reaction transfer. When a Co-Pi co-catalyst was integrated onto the surface of the 2-TaON/BiVO₄ electrode, the surface water oxidation kinetics further improved, and a highly efficient photocurrent density of 3.6 mA cm⁻² was achieved at 1.23 V vs. RHE. The largest half-cell solar energy conversion efficiency for Co-Pi/TaON/BiVO₄ was 1.19% at 0.69 V vs. RHE, corresponding to 6 times that of bare BiVO₄ (0.19% at 0.95 V vs. RHE). This study provides an available strategy to develop photoelectrochemical water splitting of BiVO₄-based photoanodes.

TaON/BiVO₄ heterojunction electrodes exhibited significant enhancement in the photoelectrochemical water oxidation.     

Selective and sensitive visible-light-prompt photoelectrochemical sensor of paracetamol based on Bi2WO6 modified with Bi and copper sulfide

Paracetamol (PA) is a ubiquitous non-steroidal anti-inflammatory drug, mainly used to treat headaches, arthritis and osteoarthritis and other diseases. In this work, a novel label free photoelectrochemical (PEC) sensor based on Bi–CuS/Bi₂WO₆ has been developed for the detection of PA, which was fabricated by a simple two-step hydrothermal process. It was found that Bi–CuS/Bi₂WO₆ with a CuS/Bi₂WO₆ heterojunction and surface plasmon resonance (SPR) effect of Bi possesses enhanced charge transfer and absorption wavelengths under visible light, particularly when compared to pristine Bi₂WO₆ films, thus producing an increase in the observed photocurrent. The photocurrent was increased after adding PA. And the photocurrent increment was linear with PA concentration in the range from 0.01–60 μM with a detection limit of 2.12 nM. Moreover, the PEC sensor also exhibited high anti-interference property and acceptable stability. In the present study, a Bi–CuS/Bi₂WO₆ photoelectrode is considered a promising candidate for carrying out PEC analysis.

When the compound is illuminated, Bi–CuS/Bi₂WO₆ generates lots of photogenerated electrons and exhibits outstanding performance for paracetamol (PA).     

Titanium phosphonate oxo-alkoxide “clusters”: solution stability and facile hydrolytic transformation into nano titania

Titanium (oxo-) alkoxide phosphonate complexes were synthesized using different titanium precursors and tert-butylphosphonic acid (tBPA) as molecular models for interaction between phosphonates and titania surfaces and to investigate the solution stability of these species. Reflux of titanium(iv) ethoxide or titanium(iv)(diisopropoxide)bis(2,4-pentadionate) with tert-butylphosphonic acid in toluene–ethanol mixture or acetone yielded seven titanium alkoxide phosphonate complexes; [Ti₅(μ₃-O)(μ₂-O)(μ-HOEt)₂(μ-OEt)₃(μ₂-OEt)(μ₃-tBPA)₃(μ₃-HtBPA)(μ₂-tBPA)₂(μ₂-HtBPA)]·3EtOH, 1, [Ti₄O(μ-OEt)₅(μ₂-OEt)₇(μ₃-tBPA)], 2, [Ti₄(μ₂-O)₂(μ-OEt)₂(μ-HOEt)₂(μ₂-tPBA)₂(μ₂-HtPBA)₆]·4EtOH, 3, [Ti₄(μ₂-O)₂(μ-OEt)₂(μ-HOEt)₂(μ₂-tPBA)₂(μ₂-HtPBA)₆]·2EtOH, 4, [Ti₆(μ₂-O)(μ₃-O)₂(μ₂-OEt)₅(μ-OEt)₆(μ₃-tBPA)₃(μ₃-HtBPA)], 5, [Ti₄(μ-ⁱOPr)₄(acac)₄(μ₂-tBPA)₄], 6 and [Ti₅(μ₄-O)(μ₂-O)₃(μ₂-OEt)₄(μ-OEt)₆(μ-HOEt)(μ₃-tBPA)]₂, 7. The binding mode of tBPA to the titanium oxo-core were either double or triple bridging or a combination of the two. No monodentate or chelating coordination was observed. ³¹P NMR spectrometry of dissolved single crystals indicates that 1 and 5 retain their solid-state structures in solution, the latter even on moderate heating, while 6 and 7 dissolved into several other forms. The complexes were found to be sensitive towards hydrolysis, proceeding in a topotactic fashion with densification of the material into plates and lamellae resulting finally in “core–shell” nanoparticles with a crystalline core (anatase) and an amorphous outer shell upon contact with water at room temperature as observed by HRTEM and AFM analyses. ³¹P NMR data supported degradation after addition of water to solutions of the complexes. Hydrolysis under different conditions affords complex oxide structures of different morphologies.

Oligonuclear Ti(iv) oxo-alkoxide-phosphonate complexes, produced by reaction of tBuPO(OH)₂ with Ti(OR)₄, are easily topotactically hydrolyzed forming intricate nanostructures.     

Highly efficient hamburger-like nanostructure of a triadic Ag/Co3O4/BiVO4 photoanode for enhanced photoelectrochemical water oxidation

The combination of a semiconductor heterojunction and oxygen evolution cocatalyst (OEC) is an important strategy to improve photoelectrochemical (PEC) water oxidation. Herein, a novel hamburger-like nanostructure of a triadic photoanode composed of BiVO₄ nanobulks, Co₃O₄ nanosheets and Ag nanoparticles (NPs), that is, Ag/Co₃O₄/BiVO₄, was designed. In our study, an interlaced 2D ultrathin p-type Co₃O₄ OEC layer was introduced onto n-type BiVO₄ to form a p–n Co₃O₄/BiVO₄ heterojunction with an internal electric field (IEF) in order to facilitate charge transport. Then the modification with Ag NPs can significantly facilitate the separation and transport of photogenerated carriers through the surface plasma resonance (SPR) effect, inhibiting the electron–hole recombination. The resulting Ag/Co₃O₄/BiVO₄ photoanodes exhibit largely enhanced PEC water oxidation performance: the photocurrent density of the ternary photoanode reaches up to 1.84 mA cm⁻² at 1.23 V vs. RHE, which is 4.60 times higher than that of the pristine BiVO₄ photoanode. The IPCE value is 2.83 times higher than that of the pristine BiVO₄ at 400 nm and the onset potential has a significant cathodic shift of 550 mV for the ternary well-constructed photoanode.

A novel hamburger-like nanostructure of a triadic photoanode Ag/Co₃O₄/BiVO₄ was designed to enhance photoelectrochemical water splitting, providing a fascinating pathway to efficiently improve the PEC conversion efficiency.     

In situ synthesis of C-doped BiVO4 with natural leaf as a template under different calcination temperatures

In this work, a series of C-doped BiVO₄ (BiVO₄-T) with natural leaf structures were synthesized by a dipping-calcination method with the leaf of Chongyang wood seedling as a template under different calcination temperatures. The structures and morphologies of BiVO₄-T were observed by FE-SEM observations. The doped carbon in BiVO₄-T was formed in situ from the natural leaf during the calcination process and the amount of doping could be regulated from 0.51–1.16 wt% by controlling the calcination temperature. It was found that the sample calcined at 600 °C (BiVO₄-600) with a C-doping content of 1.16 wt% showed the best photocatalytic degradation activity. After 120 min visible light irradiation, the photocatalytic decomposition efficiency of RhB for BiVO₄-600 is 2.2 times higher than that of no template BiVO₄. The enhanced photocatalytic performance is ascribed to the combined action of the unique morphology and doped-carbon. It is considered that the unique structures and carbon doping of BiVO₄-600 are in favor of the enhancement of visible light absorption, which was supported by UV-vis DRS. Furthermore, the C-doping can enhance the efficient separation and transfer of the photo-generated electron–hole pairs, as proved by PL measurements. This study provides a simple dipping-calcination method and found the best calcination temperature to fabricate a high-performance BiVO₄, which simultaneously achieves morphology and C-doping control in one step.

A series of C-doped BiVO₄ with natural leaf as a template were synthesized under different calcination temperatures by the dipping-calcination method, which simultaneously achieves morphology and C-doping control in one step.     

Annealing temperature effects on photoelectrochemical performance of bismuth vanadate thin film photoelectrodes

The effects of annealing treatment between 400 °C and 540 °C on crystallization behavior, grain size, electrochemical (EC) and photoelectrochemical (PEC) oxygen evolution reaction (OER) performances of bismuth vanadate (BiVO₄) thin films are investigated in this work. The results show that higher temperature leads to larger grain size, improved crystallinity, and better crystal orientation for the BiVO₄ thin film electrodes. Under air-mass 1.5 global (AM 1.5) solar light illumination, the BiVO₄ thin film prepared at a higher annealing temperature (500–540 °C) shows better PEC OER performance. Also, the OER photocurrent density increased from 0.25 mA cm⁻² to 1.27 mA cm⁻² and that of the oxidation of sulfite, a hole scavenger, increased from 1.39 to 2.53 mA cm⁻² for the samples prepared from 400 °C to 540 °C. Open-circuit photovoltage decay (OCPVD) measurement indicates that BiVO₄ samples prepared at the higher annealing temperature have less charge recombination and longer electron lifetime. However, the BiVO₄ samples prepared at lower annealing temperature have better EC performance in the absence of light illumination and more electrochemically active surface sites, which are negatively related to electrochemical double-layer capacitance (C_dl). C_dl was 0.0074 mF cm⁻² at 400 °C and it decreased to 0.0006 mF cm⁻² at 540 °C. The OER and sulfide oxidation are carefully compared and these show that the efficiency of charge transport in the bulk (η_bulk) and on the surface (η_surface) of the BiVO₄ thin film electrode are improved with the increase in the annealing temperature. The mechanism behind the light-condition-dependent role of the annealing treatment is also discussed.

The effects of annealing treatment on crystallization behavior, grain size, electrochemical (EC) and photoelectrochemical (PEC) oxygen evolution reaction (OER) performances of bismuth vanadate (BiVO₄) thin films are investigated in this work.     

Superior visible light photocatalytic performance of reticular BiVO4 synthesized via a modified sol–gel method

Reticular BiVO₄ catalysts were successfully synthesized via a modified sol–gel method. Here, citric acid (CA) was used as the chelating agent and ethylenediaminetetraacetic acid (EDTA) was used as the chelating agent and template. Furthermore, the effects of pH values and EDTA on the structure and morphology of the samples were studied. We determined that EDTA and pH played important roles in the determination of the morphology of the as-prepared BiVO₄ samples. Photocatalytic evaluation revealed that the reticular BiVO₄ exhibited superior photocatalytic performance characteristics for the degradation of methylene blue (MB) under visible-light (λ > 400 nm) exposure, about 98% of the MB was found to degrade within 50 min. Moreover, the degradation kinetics of MB was in good agreement with pseudo-first-order kinetics. The obtained apparent reaction rate constant k_app of reticular BiVO₄ was much higher than that of BiVO₄ synthesized by the citric acid sol–gel method.

Reticular BiVO₄ catalysts with superior visible light photocatalytic performance were successfully synthesized via a modified sol–gel method.     

Insight into the PEC and interfacial charge transfer kinetics at the Mo doped BiVO4 photoanodes

BiVO₄ is a promising photoanode material for the photoelectrochemical (PEC) oxidation of water; however, its poor charge transfer, transport, and slow surface catalytic activity limit the expected theoretical efficiency. Herein, we have investigated the effect of Mo doping on SnO₂ buffer layer coated BiVO₄ for PEC water splitting. SnO₂ and Mo doped BiVO₄ layers are coated with layer by layer deposition through a precursor solution based spin coating technique followed by annealing. At 5% doping of Mo, the sample (SBM5) shows a maximum current density of 1.65 mA cm⁻² at 1.64 V vs. RHEl in 0.1 M phosphate buffer solution under AM 1.5 G solar simulator, which is about 154% improvement over the sample without Mo (SBM0). The significant improvement in the photocurrent upon Mo doping is due to the improvement of various bulk and interfacial properties in the materials as measured by UV-vis spectroscopy, electrochemical impedance spectroscopy (EIS), Mott–Schottky analysis, and open-circuit photovoltage (OCPV). The charge transfer kinetics at the BiVO₄/electrolyte interface are investigated to simulate the oxygen evolution process in photoelectrochemical water oxidation in the feedback mode of scanning electrochemical microscopy (SECM) using 2 mM [Fe(CN)₆]³⁻ as the redox couple. SECM investigation reveals a significant improvement in effective hole transfer rate constant from 2.18 cm s⁻¹ to 7.56 cm s⁻¹ for the hole transfer reaction from the valence band of BiVO₄ to [Fe(CN)₆]⁴⁻ to oxidize into [Fe(CN)₆]³⁻ with the Mo doping in BiVO₄. Results suggest that Mo⁶⁺ doping facilitates the hole transfer and suppresses the back reaction. The synergistic effect of fast forward and backward conversion of Mo⁶⁺ to Mo⁵⁺ expected to facilitate the V⁵⁺ to V⁴⁺ which has an important step to improve the photocurrent.

BiVO₄ is a promising photoanode material for the photoelectrochemical (PEC) oxidation of water; however, its poor charge transfer, transport, and slow surface catalytic activity limit the expected theoretical efficiency.     

Interrogating solar photoelectrocatalysis on an exfoliated graphite–BiVO4/ZnO composite electrode towards water treatment

A novel photoanode consisting of an exfoliated graphite–BiVO₄/ZnO heterostructured nanocomposite was fabricated. The material was characterised with scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). Photoelectrochemical studies were carried out with cyclic/linear sweep voltammetry and chronoamperometry. The solar photoelectrochemical properties of the heterojunction photoanode were investigated through the degradation of rhodamine B in water. The results revealed that the nanoparticles of BiVO₄ and ZnO were well entrapped within the interlayers of the exfoliated graphite (EG) sheets. Improved charge separation was achieved in the EG–BiVO₄/ZnO composite electrode which resulted in superior photoelectrochemical performance than individual BiVO₄ and ZnO electrodes. A higher degradation efficiency of 91% of rhodamine B was recorded using the composite electrode with the application of 10 mA cm⁻² current density and a solution pH of 7. The highest total organic carbon removal of 74% was also recorded with the EG–BiVO₄/ZnO. Data from scavenger studies were used to support the proposed mechanism of degradation. The electrode has high stability and reusability and hence lends itself to applications in photoelectrocatalysis, especially in water treatment.

Band alignment between ZnO and BiVO₄ on exfoliated graphite (EG) support.     

Ag2O-decorated electrospun BiVO4 nanofibers with enhanced photocatalytic performance

Semiconductor photocatalysts are emerging as tools for pollutant degradation in industrial wastewater, air purification, antibacterial applications, etc. due to their use of visible light, which is abundant in sunlight. Here, we report a new type of p–n junction Ag₂O/BiVO₄ heterogeneous nanostructured photocatalyst with enhanced photocatalytic performance. P-type Ag₂O nanoparticles were in situ reduced and assembled on the surface of electrospun BiVO₄ nanofibers using ultraviolet (UV) irradiation; this process hindered the recombination of localized photogenerated electron–hole pairs, and hence resulted in the enhanced photocatalytic activity of the BiVO₄/Ag₂O nanocomposites. The photocatalytic activities of the obtained BiVO₄ and BiVO₄/Ag₂O nanocomposites were assessed by measuring the degradation of rhodamine B (RhB) under visible light. The 10 wt% Ag₂O/BiVO₄ sample yielded the optimum degradation of RhB (98.47%), much higher than that yielded by pure BiVO₄ nanofibers (64.67%). No obvious change in the XRD pattern of an Ag₂O/BiVO₄ sample occurred as a result of its use in the photocatalytic reaction, indicating its excellent stability. The high photocatalytic performance observed was attributed to the large surface-to-volume ratio of the essentially one-dimensional electrospun BiVO₄ nanofibers and to the in situ growth of p-type Ag₂O on the surface of the n-type BiVO₄ nanofibers.

Ag₂O doped electrospun BiVO₄ nanofibers with p–n junction heterogeneous structures show enhanced photocatalytic activity under visible light (photocatalytic efficiency: 98.47% within 100 min) and good cycling stability.     

Co2+ substituted for Bi3+ in BiVO4 and its enhanced photocatalytic activity under visible LED light irradiation

We investigated the fabrication of Co-doped BiVO₄ (Bi_1−xCo_xVO_4+δ, 0.05 < x < 0.5) by the substitution of Co ions for Bi sites in BiVO₄. The X-ray diffraction (XRD), Raman, and X-ray photoelectron spectroscopy (XPS) results indicated that the substitution of Co²⁺ ions for Bi³⁺ sites in BiVO₄ was successful, although a change in the crystal phase of BiVO₄ did not occur. UV-vis DRS and PL results suggested that the Co-incorporation could slightly improve the visible light absorption of BiVO₄ and induce the separation of photoinduced electron–hole pairs; therefore, a significant enhancement of photocatalytic performance was achieved. The Bi_0.8Co_0.2VO_4+δ sample showed superior photocatalytic activity in comparison with other samples, achieving 96.78% methylene blue (MB) removal within 180 min. In addition, the proposed mechanism of improved photocatalytic activities and the stability of the catalyst were also investigated.

We investigated the fabrication of Co-doped BiVO₄ (Bi_1−xCo_xVO_4+δ, 0.05 < x < 0.5) by the substitution of Co ions for Bi sites in BiVO₄.     

Z-scheme BiVO4/Ag/Ag2S composites with enhanced photocatalytic efficiency under visible light

The Z-scheme BiVO₄/Ag/Ag₂S photocatalyst was fabricated via a two-step route. The as-prepared samples were characterized by XRD, FE-SEM, HRTEM, XPS and UV-vis diffuse reflectance spectroscopy. The results of PL and photocurrent response tests demonstrate that the ternary BiVO₄/Ag/Ag₂S composites had a high separation and migration efficiency of photoexcited carriers. As a result, the ternary photocatalyst exhibits enhanced photocatalytic activity for decomposing Rhodamine B (RhB) under LED light (420 nm) irradiation. The results of trapping experiments demonstrate both h⁺ and ˙OH play crucial roles in decomposing RhB molecules. Additionally, the energy band structures and density of states (DOS) of BiVO₄ and Ag₂S were investigated via the density functional theory (DFT) method. Finally, a Z-scheme electron migration mechanism of BiVO₄ → Ag → Ag₂S was proposed based on the experimental and calculated results.

The Z-scheme BiVO₄/Ag/Ag₂S photocatalyst was fabricated via a two-step route.     

Facile and rapid synthesis of a novel spindle-like heterojunction BiVO4 showing enhanced visible-light-driven photoactivity

A spindle-like monoclinic–tetragonal heterojunction BiVO₄ was successfully synthesized by a pressure-controllable microwave method. The as-prepared BiVO₄ samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy, transient photocurrent responses and electrochemical impedance spectroscopy (EIS). The visible-light-driven photocatalytic activity of the BiVO₄ samples was evaluated for the degradation of Rhodamine B (RhB) and tetracycline (TC). The synthesis process needs microwave irradiation for only 10 min without the addition of any auxiliary reagent, pH adjustment, and calcination. The as-prepared spindle-like monoclinic–tetragonal heterojunction BiVO₄ exhibits excellent photocatalytic activity for the degradation of both RhB and TC. The photocatalytic degradation rates of RhB and TC over spindle-like BiVO₄ are 1.77 and 1.64 times higher, respectively, than that measured over monoclinic BiVO₄. The enhanced photocatalytic activity is mainly attributed to the fact that the existence of a heterojunction effectively promotes the separation of photo-generated carriers and extends the visible-light absorption of BiVO₄.

A novel spindle-like monoclinic–tetragonal BiVO₄ heterojunction is rapidly synthesized via a pressure-controllable microwave method.     

A mechanochemically synthesized porous organic polymer derived CQD/chitosan–graphene composite film electrode for electrochemiluminescence determination of dopamine

Herein, we explore a new carbon source for preparation of carbon quantum dots (CQDs) with controllable composition using a porous organic polymer (POP) derived porous carbon via a nitric acid oxidation method. The POP used for the preparation of CQDs was synthesized by mechanochemical Friedel–Crafts alkylation under solvent free conditions. Using the as-prepared CQDs, we develop a simple and effective electrochemiluminescence (ECL) detection method for dopamine (DA) using a CQD/chitosan–graphene composite modified glassy carbon electrode (GCE). Both the electrochemical and ECL behaviors were studied in detail with ammonium persulfate as a coreactant. The complementary structure and synergistic function of the composite give the ECL sensor special properties. Apart from the high stability, it also presents good repeatability and high sensitivity to DA with a wide linear range from 0.06 to 1.6 μM. And a satisfactory detection limit of 0.028 μM (S/N = 3) was achieved for the prepared sensor. Furthermore, the ECL also shows high selectivity toward DA with an excellent interference resistance ability at a high concentration ratio of 100 (C_interference : C_DA = 100). In addition, the ECL sensor was successfully applied for effective detection and quantitative analysis of the actual dopamine in human body fluids for disease diagnosis and pathological studies.

CQDs were obtained from a POP derived porous carbon via nitric acid oxidation. CQDs/CG composite film with special properties were fabricated and used for ECL detection of DA in human body fluids.     

Constructing a TiO2/PDA core/shell nanorod array electrode as a highly sensitive and stable photoelectrochemical glucose biosensor

Developing stable PEC glucose biosensors with high sensitivity and low detection limit is highly desirable in the biosensor field. Herein, a highly stable and sensitive enzymatic glucose photoelectrochemical biosensor is rationally designed and fabricated by constructing TiO₂/PDA core/shell nanorod arrays. The TiO₂ nanorod as the core has the advantages of increasing charge transportation towards interfaces and enhancing the absorption of incident sunlight due to its single-crystal nature and one dimensional array structure. The PDA shell not only induces a rapid charge transfer across the interfaces but also stabilizes the biosensor performance by avoiding the decomposition of enzymes induced by the strong oxidizing holes from the TiO₂ core. A remarkable performance with an ultrahigh sensitivity of 57.72 μA mM⁻¹ cm⁻², a linear range of 0.2–1.0 mM, a glucose detection limit of 0.0285 mM (S/N = 3) and a high sensitivity of 8.75 μA mM⁻¹ cm⁻² in a dynamic range of 1.0–6.0 mM were obtained for the glucose detection. This study might provide a strategy for constructing inorganic/organic core/shell structures with a satisfactory PEC performance.

Developing stable PEC glucose biosensors with high sensitivity and low detection limit is highly desirable in the biosensor field.     

Free-standing graphene/bismuth vanadate monolith composite as a binder-free electrode for symmetrical supercapacitors

Preparation of new types of electrode material is of great importance to supercapacitors. Herein, a graphene/bismuth vanadate (GR/BiVO₄) free-standing monolith composite has been prepared via a hydrothermal process. Flexible GR sheets act as a skeleton in the GR/BiVO₄ monolith composites. When used as a binder-free electrode in a three-electrode system, the GR/BiVO₄ composite electrode can provide an impressive specific capacitance of 479 F g⁻¹ in a potential window of −1.1 to 0.7 V vs. SCE at a current density of 5 A g⁻¹. A symmetrical supercapacitor cell which can be reversibly charged–discharged at a cell voltage of 1.6 V has been assembled based on this GR/BiVO₄ monolith composite. The symmetrical capacitor can deliver an energy density of 45.69 W h kg⁻¹ at a power density of 800 W kg⁻¹. Moreover, it ensures rapid energy delivery of 10.75 W h kg⁻¹ with a power density of 40 kW kg⁻¹.

A symmetrical supercapacitor with a high energy density has been assembled based on a free-standing GR/BiVO₄ monolith composite.