In situ synthesis of molybdenum carbide/N-doped carbon hybrids as an efficient hydrogen-evolution electrocatalyst

The development of non-precious metal based electrocatalysts for the hydrogen evolution reaction (HER) has received more and more attention over recent years owing to energy and environmental issues, and Mo based materials have been explored as a promising candidate. In this work, molybdenum carbide/N-doped carbon hybrids (Mo₂C@NC) were synthesized facilely via one-step high-temperature pyrolysis by adjusting the mass ratio of urea and ammonium molybdate. The Mo₂C@NC consisted of ultrasmall nanoparticles encapsulated by N-doped carbon, which had high specific surface area. They all exhibited efficient HER activity, and the Mo₂C@NC with a mass ratio of 160 (Mo₂C@NC-160) showed the best HER activity, with a low overpotential of 90 mV to reach 10 mA cm⁻² and a small Tafel slope of 50 mV dec⁻¹, which was one of the most active reported Mo₂C-based electrocatalysts. The excellent HER activity of Mo₂C@NC-160 was attributed to the following features: (1) the highly dispersed ultrasmall Mo₂C nanoparticles, which exhibited high electrochemically active surface areas; (2) the synergistic effect of the N-doped carbon shell/matrix, which facilitated the electron transport.

The molybdenum carbide/N-doped carbon hybrids (Mo₂C@NC) were synthesized facilely via one-step high-temperature pyrolysis, which exhibited efficient electrocatalytic hydrogen evolution performance.     

The structure and self-regeneration performance of Salix psammophila-activated carbon modified by Ag and N co-doped TiO2

In this study, Salix psammophila activated carbon (AC) was modified by immersing it in an AgNO₃ solution and coating it with an N-doped TiO₂ film to improve its self-regeneration performance in visible light. Ag⁺ was adsorbed and reduced to Ag nanoparticles by AC. Ti element only existed as Ti⁴⁺, and N element was incorporated into TiO₂ mainly in the form of interstitial nitrogen. The photodegradation of Ag-N-TiO₂-AC (AC coated with Ag and N co-modified TiO₂) was enhanced under visible light irradiation because of its three inherent structures: (1) Ag and N co-modified TiO₂ had a smaller average crystal size; (2) with a low bandgap (1.59 eV), the photoresponse region of Ag and N co-modified TiO₂ was greatly extended; (3) the lifetime of the photogenerated holes was increased. With the increase in the AgNO₃ dosage, the Ag-N-TiO₂-AC photodegradation increased, while its adsorption decreased. Because of these synergistic effects, 0.05Ag-0.1N-TiO₂-AC (where 0.05 is the dosage of AgNO₃, g) presented the best self-regeneration performance under visible light irradiation.

In this study, Salix psammophila activated carbon (AC) was modified by immersing it in an AgNO₃ solution and coating it with an N-doped TiO₂ film to improve its self-regeneration performance in visible light.     

Tuning the microstructural and magnetic properties of CoFe2O4/SiO2 nanocomposites by Cu2+ doping

Co–Cu ferrite is a promising functional material in many practical applications, and its physical properties can be tailored by changing its composition. In this work, Co_1−xCu_xFe₂O₄ (0 ≤ x ≤ 0.3) nanoparticles (NPs) embedded in a SiO₂ matrix were prepared by a sol–gel method. The effect of a small Cu²⁺ doping content on their microstructure and magnetic properties was studied using XRD, TEM, Mössbauer spectroscopy, and VSM. It was found that single cubic Co_1−xCu_xFe₂O₄ ferrite was formed in amorphous SiO₂ matrix. The average crystallite size of Co_1−xCu_xFe₂O₄ increased from 18 to 36 nm as Cu²⁺ doping content x increased from 0 to 0.3. Mössbauer spectroscopy indicated that the occupancy of Cu²⁺ ions at the octahedral B sites led to a slight deformation of octahedral symmetry, and Cu²⁺doping resulted in cation migration between octahedral A and tetrahedral B sites. With Cu²⁺ content increasing, the saturation magnetization (M_s) first increased, then tended to decrease, while the coercivity (H_c) decreased continuously, which was associated with the cation migration. The results suggest that the Cu²⁺ doping content in Co_1−xCu_xFe₂O₄ NPs plays an important role in its magnetic properties.

The Cu²⁺ doping content in Co_1−xCu_xFe₂O₄/SiO₂ plays an important role in tuning hyperfine interaction and magnetic properties.     

An exclusive deposition method of silver nanoparticles on TiO2 particles via low-temperature decomposition of silver-alkyldiamine complexes in aqueous media

An exclusive deposition method of Ag nanoparticles (NPs) on TiO₂ particles has been developed. Ag NPs supported on TiO₂ particles, Ag_x/TiO₂, with various Ag weight ratios versus total weights of Ag and TiO₂ between x = 2 and 16 wt% are prepared via low-temperature thermal decomposition of Ag(i)–alkyldiamine complexes generated by a reaction between AgNO₃ and N,N-dimethyl-1,3-propanediamine (dmpda) in an aqueous medium suspending TiO₂ particles. The thermal decomposition of the Ag(i)–alkyldiamine complexes is accelerated by TiO₂ particles in the dark, indicating that the reaction catalytically occurs on the TiO₂ surfaces. Under optimised reaction conditions, the thermal decomposition of the complex precursors is completed within 3 hours at 70 °C, and Ag NPs are almost exclusively deposited on TiO₂ particles with high conversion efficiencies (≥95%) of the precursor complexes. The thermal decomposition rates of the precursor complexes are strongly influenced by the chemical structure of a family of water-soluble dmpda analogues, and dmpda with both primary and tertiary amino groups is adopted as a suitable candidate for the exclusive deposition method. The number-averaged particle sizes of the Ag NPs are 6.4, 8.4, 11.8 and 15.2 nm in the cases of Ag_x/TiO₂, x = 2, 4, 8 and 16, respectively. To the best of our knowledge, the as-prepared Ag_x/TiO₂ samples show one of the highest catalytic abilities for the hydrogenation reduction of 4-nitrophenol into 4-aminophenol as a model reaction catalysed by Ag NPs.

The low-temperature decomposition of Ag(i)–dmpda complexes catalytically occurs on TiO₂ surfaces in water.     

Compact TiO2 films with sandwiched Ag nanoparticles as electron-collecting layer in planar type perovskite solar cells: improvement in efficiency and stability

Fabrication of perovskite solar cells (PSCs) in a simple way with high efficiency and stability remains a challenge. In this study, silver nanoparticles (Ag NPs) were sandwiched between two compact TiO₂ layers through a facile process of spin-coating an ethanolic AgNO₃ solution, followed by thermal annealing. The presence of Ag NPs in the electron-transporting layer of TiO₂ improved the light input to the device, the morphology of the perovskite film prepared on top, and eliminated leakage current. Photoluminescence and electron mobility studies revealed that the incorporation of Ag NPs in the ETL of the planar PSC device facilitated the electron–hole separation and promoted charge extraction and transport from perovskite to ETL. Hysteresis-free devices with incorporated Ag NPs gave a high average short-circuit current density (J_sc) of 22.91 ± 0.39 mA cm⁻² and maximum power conversion efficiency of 17.25%. The devices also showed enhanced stability versus a control device without embedded Ag NPs. The possible reasons for the improvement are analyzed and discussed.

Embedding silver nanoparticles in the compact TiO₂ layer effectively improves the efficiency and stability of a perovskite solar cell.     

N-doped mixed Co,Ni-oxides with petal structure as effective catalysts for hydrogen and oxygen evolution by water splitting

Developing electrocatalytic nanomaterials for green H₂ energy is inseparable from the exploration of novel materials and internal mechanisms for catalytic enhancement. In this work, nano-petal N-doped bi-metal (Ni, Co) and bi-valence (+2, +3) (Ni_1−xCo_x)²⁺Co₂³⁺O₄ compounds have been in situ grown on the surface of Ni foam. The N³⁻ atoms originate from the amino group in urea and doped in the compound during annealing. The as-synthesized N-doped (Ni_1−xCo_x)²⁺Co₂³⁺O₄ nano-petals demonstrate commendable hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) bi-functional catalytic efficiency and stability. Electrochemical measurements confirm that the nitrogen doping significantly improves the catalytic kinetics and the surface area. Density functional theory calculations reveal that the improved HER and OER kinetics is not only due to the synergistic effect of bi-metal and bi-valence, as well as the introduction of defects such as oxygen vacancies, but also it more depends on the shortened bond length between the nitrogen N³⁻ atoms and the metal atoms, and the increased electron density of the metal atoms attached to the N³⁻ atoms. In other words, the change of lattice parameters caused by nitrogen doping is more conducive to the catalytic enhancement than the synergistic effect brought by bi-metal. This study provides an experimental and theoretical reference for the design of bi-functional electrocatalytic nanomaterials.

Developing electrocatalytic nanomaterials for green H₂ energy is inseparable from the exploration of novel materials and internal mechanisms for catalytic enhancement.     

Black TiO2 nanotube arrays fabricated by electrochemical self-doping and their photoelectrochemical performance

Herein, black TiO₂ nanotube arrays (NTAs) were fabricated using electrochemical self-doping approaches, and characterized systemically by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), UV-visible absorption spectroscopy and photoluminescence spectroscopy (PL). The as-obtained black TiO₂ nanotube arrays (NTAs) exhibited stronger absorption in the visible-light region, a better separation rate of light-induced carriers, and higher electrical conductivity than TiO₂ nanotube arrays (NTAs). These characteristics cause black TiO₂ nanotube array (NTA) electrodes to have higher photoelectrocatalytic activity for degrading anthraquinone dye (reactive brilliant blue KN-R) than the TiO₂ nanotube array (NTA) electrode. Furthermore, a synergetic action between photocatalysis and electrocatalysis was also observed. The black TiO₂ nanotube array (NTA) electrode is considered to be a promising photoanode for the treatment of organic pollutants.

It was found that the removal of KN-R on black TiO₂ NTAs electrodes can be improved by combination of electro-enhanced photocatalysis and electrochemical oxidation at high bias.     

Rapid and continuous fabrication of TiO2 nanoparticles encapsulated by polyimide fine particles using a multistep flow-system and their application

PI fine particles encapsulating a large number of TiO₂ nanoparticles (PI FPs/TiO₂ NPs) were successfully fabricated rapidly and continuously by the emulsion re-precipitation method using a multistep flow synthetic system. The fabricated material, PI FPs/TiO₂ NPs, was spherical in structure with a diameter of 214 nm, and the mean size of TiO₂ NPs was 5.2 nm. Line scan elemental analysis with SEM-EDX showed that the TiO₂ NPs were disproportionately embedded near the surface of the PI FPs. UV-vis transmission spectra revealed high UV shielding efficiency of the PI FPs/TiO₂ NPs as the NPs are located near the surface.

We rapidly and continuously fabricated TiO₂ nanoparticles encapsulated by polymer fine particles, and the fabricated nanomaterials showed high UV shielding efficiency.     

In situ growth of carbon dots on TiO2 nanotube arrays for PEC enzyme biosensors with visible light response

Carbon dots (CDs) were grown in situ on secondary anodized TiO₂ nanotube arrays (TiO₂ NTAs) via a hydrothermal method. The combination of CDs and TiO₂ NTAs enhanced the photoelectrochemical performance. Morphology, structure, and elemental composition of the CDs were characterized. No simple physical adsorption was found between the CDs and TiO₂, but chemical bonds were formed. UV-vis absorption and fluorescence spectroscopy showed that the CDs could enhance the absorption of TiO₂ in the visible and near-infrared regions. Owing to their up-conversion fluorescence properties, the CDs could convert low-energy photon absorption into high-energy photons, which may be used to excite TiO₂ to produce a stronger photoelectric response. Moreover, the CDs could effectively transport electrons and accept holes, thus contributing to the effective separation of electrons and holes during photoexcitation. Finally, the PEC biosensor was prepared by immobilizing glucose oxidase (GOx) on the surface of the composite. The PEC biosensor exhibited a broad range of 0.1–18 mM with a detection limit of 0.027 mM under visible irradiation because the composite material reflected strong light absorption for visible light, good conductivity, and good biocompatibility.

Carbon dots (CDs) were grown in situ on secondary anodized TiO₂ nanotube arrays (TiO₂ NTAs) via a hydrothermal method.     

In vitro cytotoxicity and antibiotic application of green route surface modified ferromagnetic TiO2 nanoparticles

The enormous numbers of applications of TiO₂ nanoparticles (NPs) cause concern about their risk to the environment and human health. Consequently, motivated by the necessity of searching for new sources of TiO₂ NPs of low cytotoxicity with antibacterial activity, we synthesized TiO₂ NPs by a green route using a solution of titanium(iv) isopropoxide as a precursor and an aqueous extract of Artocarpus heterophyllus leaf as a reducing and surface modifying agent. We investigated their structure, shape, size, and magnetic properties, and evaluated their antibiotic application and cytotoxicity. The synthesized TiO₂ NPs were applied against two Gram-negative bacteria (E. coli and S. typhimurium) and two Gram-positive bacteria (S. aureus and B. subtilis) to observe their antibacterial activity; and eventually clear zones of inhibition formed by the TiO₂ NPs were obtained. Moreover, after exposing the synthesized TiO₂ NPs to HeLa cells (carcinoma cells) and Vero cells (normal cells), no toxic effect was found up to a dose of 1000 mg L⁻¹, indicating the safe use of the samples up to at least 1000 mg L⁻¹. However, toxic effects on HeLa cells and Vero cells were observed at doses of 2000 mg L⁻¹ and 3000 mg L⁻¹, respectively. These results indicate the safe use of Artocarpus heterophyllus leaf extract mediated synthesized TiO₂ NPs in their potential applications.

Artocarpus heterophyllus leaf extract mediated green synthesized TiO₂ nanoparticles exhibit less toxicity with high antibacterial activity.     

Synthesis of core–shell N-TiO2@CuOx with enhanced visible light photocatalytic performance

In this paper, a core–shell N-TiO₂@CuO_x nanomaterial with increased visible light photocatalytic activity was successfully synthesized using a simple method. By synthesizing ammonium titanyl oxalate as a precursor, N-doped TiO₂ can be prepared, then the core–shell structure of N-TiO₂@CuO_x with a catalyst loading of Cu on its surface was prepared using a precipitation method. It was characterized in detail using XRD, TEM, BET, XPS and H₂-TPR, while its photocatalytic activity was evaluated using the probe reaction of the degradation of methyl orange. We found that the core–shell N-TiO₂@CuO_x nanomaterial can lessen the TiO₂ energy band-gap width due to the N-doping, as well as remarkably improving the photo-degradation activity due to a certain loading of Cu on the surfaces of N-TiO₂ supports. Therefore, a preparation method for a novel N, Cu co-doped TiO₂ photocatalyst with a core–shell structure and efficient photocatalytic performance has been provided.

In this paper, a core–shell N-TiO₂@CuO_x nanomaterial with increased visible light photocatalytic activity was successfully synthesized using a simple method.     

A Co-MOF-derived Co9S8@NS-C electrocatalyst for efficient hydrogen evolution reaction

The exploitation of efficient hydrogen evolution reaction (HER) electrocatalysts has become increasingly urgent and imperative; however, it is also challenging for high-performance sustainable clean energy applications. Herein, novel Co₉S₈ nanoparticles embedded in a porous N,S-dual doped carbon composite (abbr. Co₉S₈@NS-C-900) were fabricated by the pyrolysis of a single crystal Co-MOF assisted with thiourea. Due to the synergistic benefit of combining Co₉S₈ nanoparticles with N,S-dual doped carbon, the composite showed efficient HER electrocatalytic activities and long-term durability in an alkaline solution. It shows a small overpotential of −86.4 mV at a current density of 10.0 mA cm⁻², a small Tafel slope of 81.1 mV dec⁻¹, and a large exchange current density (J₀) of 0.40 mA cm⁻², which are comparable to those of Pt/C. More importantly, due to the protection of Co₉S₈ nanoparticles by the N,S-dual doped carbon shell, the Co₉S₈@NS-C-900 catalyst displays excellent long-term durability. There is almost no decay in HER activities after 1000 potential cycles or it retains 99.5% of the initial current after 48 h.

A porous Co₉S₈@NS-C-900 composite was fabricated by the pyrolysis of crystal Co-MOF involving thiourea. The composite exhibits efficient electrocatalytic activities and long-term durabilities towards HER in alkaline electrolytes.     

Synthesis and characterization of nickel-doped ceria nanoparticles with improved surface reducibility

Nickel-doped ceria nanoparticles (Ni_0.1Ce_0.9O_2−x NPs) were fabricated from Schiff-base complexes and characterized by various microscopic and spectroscopic methods. Clear evidence is provided for incorporation of nickel ions in the ceria lattice in the form of Ni³⁺ species which is considered as the hole trapped state of Ni²⁺. The Ni_0.1Ce_0.9O_2−x NPs exhibit enhanced reducibility in H₂ as compared to conventional ceria-supported Ni particles, while in O₂ the dopant nickel cations are oxidized at higher valence than the supported ones.

Nickel-doped ceria nanoparticles (Ni_0.1Ce_0.9O_2−x NPs) were fabricated from Schiff-base complexes and characterized by various microscopic and spectroscopic methods.     

Nanostructured N doped TiO2 efficient stable catalyst for Kabachnik–Fields reaction under microwave irradiation

Herein, we report nitrogen-doped TiO₂ (N-TiO₂) solid-acid nanocatalysts with heterogeneous structure employed for the solvent-free synthesis of α-aminophosphonates through Kabachnik–Fields reaction. N-TiO₂ were synthesized by direct amination using triethylamine as a source of nitrogen at low temperature and optimized by varying the volume ratios of TiCl₄, methanol, water, and triethylamine, under identical conditions. An X-ray diffraction (XRD) study showed the formation of a rutile phase and the crystalline size is 10 nm. The nanostructural features of N-TiO₂ were examined by HR-TEM analysis, which showed they had rod-like morphology with a diameter of ∼7 to 10 nm. Diffuse reflectance spectra show the extended absorbance in the visible region with a narrowing in the band gap of 2.85 eV, and the high resolution XPS spectrum of the N 1s region confirmed successful doping of N in the TiO₂ lattice. More significantly, we found that as-synthesized N-TiO₂ showed significantly higher catalytic activity than commercially available TiO₂ for the synthesis of a novel series of α-amino phosphonates via Kabachnik–Fields reaction under microwave irradiation conditions. The improved catalytic activity is due to the presence of strong and Bronsted acid sites on a porous nanorod surface. This work signifies N-TiO₂ is an efficient stable catalyst for the synthesis of α-aminophosphonate derivatives.

Herein, we report nitrogen-doped TiO₂ (N-TiO₂) solid-acid nanocatalysts with heterogeneous structure employed for the solvent-free synthesis of α-aminophosphonates through Kabachnik–Fields reaction.     

Au@Co2P core/shell nanoparticles as a nano-electrocatalyst for enhancing the oxygen evolution reaction

Core/shell nanoparticles (NPs) of Au@Co₂P, each comprising a Au core with a Co₂P shell, were prepared, and shown to efficiently catalyze the oxygen evolution reaction (OER). In particular, Au@Co₂P has a small overpotential of 321 mV at 10 mA cm⁻² in 1 M KOH aqueous solution at room temperature, which is about 95 mV less than pure Co₂P. More importantly, the Tafel slope of Au@Co₂P, at 57 mV dec⁻¹, is 44 mV dec⁻¹ lower than that of Co₂P. Hence, Au@Co₂P outperforms Co₂P drastically in practical production when a high current density is required.

Au@Co₂P core/shell nanoparticles were designed and prepared to improve the oxygen evolution reaction performance.     

Interior engineering of seaweed-derived N-doped versatile carbonaceous beads with CoxOy for universal organic pollutant degradation

The rational optimization of catalytic composites with excellent catalytic activities and long-term cycling stabilities for environmental remediation is still maintained as highly desired but is an ongoing challenge. Here, seaweed-derived N-doped versatile carbonaceous beads with Co_xO_y (Co-NC-0.25-700 °C) are employed as a novel catalyst to activate peroxymonosulfate (PMS) for methylene blue (MB) degradation. Profiting from the improved structure–activity relationship and the synergistic effects between the “egg-box” structure and the Co_xO_y loaded on the N-doped carbonaceous beads, Co-NC-0.25-700 °C exhibited relatively high performance and comparative long-term stability. The universal applicability of Co-NC-0.25-700 °C was investigated by degrading other types of organic pollutants in various systems. For this type of newly fabricated high-performance versatile composites, structure–property relationships were plausibly proposed. Notably, the degradation efficiency and the catalyst structure could be tailored by the amount of polyethyleneimine (PEI) introduced in the preparation process and by the pyrolysis temperature. More favorably, the coupling of the magnetic properties and bead-like shape endows the resultant composites with remarkable reusability and recyclability, as compared to powder state materials. Another interesting finding is that MB degradation over Co-NC-0.25-700 °C is minimally affected by common ions (Cl⁻, NO₃⁻, SO₄²⁻, etc.), and holds a certain catalytic activity under the background conditions of two simulated real water conditions (running water and seawater). Of particular interest, a microreactor filled with Co-NC-0.25-700 °C was utilized as a verification model for practical applications of the reaction in continuous-flow. More far-reaching, the simulations of actual water conditions and the design of a continuous-flow reactor represent a giant step towards universal applications for organic pollution treatment.

Interior engineering of seaweed-derived N-doped versatile carbonaceous beads with Co_xO_y formed by simple co-crosslinking and pyrolysis procedures are utilized for the degradation of various organic pollutants via peroxymonosulfate (PMS) activation.     

Controlling the oxidation state of molybdenum oxide nanoparticles prepared by ionic liquid/metal sputtering to enhance plasmon-induced charge separation

Nanoparticles composed of molybdenum oxide, MoO_x, were successfully prepared by room-temperature ionic liquid (RTIL)/metal sputtering followed by heat treatment. Hydroxyl groups in RTIL molecules retarded the coalescence between MoO_x NPs during heat treatment at 473 K in air, while the oxidation state of Mo species in MoO_x nanoparticles (NPs) could be modified by changing the heat treatment time. An LSPR peak was observed at 840 nm in the near-IR region for MoO_x NPs of 55 nm or larger in size that were annealed in a hydroxyl-functionalized RTIL. Photoexcitation of the LSPR peak of MoO_x NPs induced electron transfer from NPs to ITO electrodes.

MoO_x NPs, prepared by sputtering Mo metal on a room-temperature ionic liquid (RTIL) followed by heating in air, produced anodic photocurrents with the excitation of their LSPR peak.     

Electrochemical properties of TiOx/rGO composite as an electrode for supercapacitors

Transition metal oxides are known as the active materials for capacitors. As a class of transition metal oxide, Magnéli phase TiO_x is particularly attractive because of its excellent conductivity. This work investigated the electrochemical characteristics of TiO_x and its composite with reduced graphene oxide (rGO). Two types of TiO_x, i.e. low and high reduction extent, were employed in this research. Electrochemical impedance spectroscopy revealed that TiO_x with lower reduction extent delivered higher electro-activity and charge transfer resistance at the same time. However, combining 10% of low-reduction state TiO_x and rGO using a simple mixing process delivered a high specific capacitance (98.8 F g⁻¹), which was higher than that of standalone rGO (49.5 F g⁻¹). A further improvement in the specific capacitance (102.6 F g⁻¹) was given by adding PEDOT:PSS conductive polymer. Results of this research gave a basic understanding in the electrochemical behavior of Magnéli phase TiO_x for the utilization of this material as supercapacitor in the future.

This work investigated the electrochemical characteristics of TiO_x and its composite with reduced graphene oxide.     

Surface plasmon-driven photoelectrochemical water splitting of a Ag/TiO2 nanoplate photoanode

A silver/titanium dioxide nanoplate (Ag/TiO₂ NP) photoelectrode was designed and fabricated from vertically aligned TiO₂ nanoplates (NP) decorated with silver nanoparticles (NPs) through a simple hydrothermal synthesis and electrodeposition route. The electrodeposition times of Ag NPs on the TiO₂ NP were crucial for surface plasmon-driven photoelectrochemical (PEC) water splitting performance. The Ag/TiO₂ NP at the optimal deposition time of 5 min with a Ag element content of 0.53 wt% demonstrated a remarkably high photocurrent density of 0.35 mA cm⁻² at 1.23 V vs. RHE under AM 1.5G illumination, which was 5 fold higher than that of the pristine TiO₂ NP. It was clear that the enhanced light absorption properties and PEC performance for Ag/TiO₂ NP could be effectively adjusted by simply controlling the loading amounts of metallic Ag NPs (average size of 10–30 nm) at different electrodeposition times. The superior PEC performance of the Ag/TiO₂ NP photoanode was attributed to the synergistic effects of the plasmonic Ag NPs and the TiO₂ nanoplate. Interestingly, the plasmonic effect of Ag NPs not only increased the visible-light response (λ_max = 570 nm) of TiO₂ but also provided hot electrons to promote photocurrent generation and suppress charge recombination. Importantly, this study offers a potentially efficient strategy for the design and fabrication of a new type of TiO₂ hybrid nanostructure with a plasmonic enhancement for PEC water splitting.

A hybrid nanostructure Ag/TiO₂ photoelectrode for PEC water splitting with a remarkable high photocurrent density, 0.35 mA cm⁻² (5 fold higher than that of the pristine TiO₂ photoeletrode) was fabricated by a facile one-pot hydrothermal and electrodeposition method.     

Growth and properties of spinel structure Zn1.8Co0.2TiO4 single crystals by the optical floating zone method

The spinel structure Zn_1.8Co_0.2TiO₄ single crystals with 5 mm diameter and 30 mm length were successfully grown by an optical floating zone method. The as-grown crystals were characterized by X-ray diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS). Some Zn²⁺ ions at tetrahedral and octahedral sites should be replaced by doped transition metal Co²⁺ ions. The temperature-dependent Raman spectra of spinel Zn_1.8Co_0.2TiO₄ crystals were also described. The optical phonon behaviors of Zn_1.8Co_0.2TiO₄ are stable within the temperature range. The magnetic properties of Zn_1.8Co_0.2TiO₄ were investigated by using Physical Property Measurement System.

The spinel structure Zn_1.8Co_0.2TiO₄ single crystals with 5 mm diameter and 30 mm length were successfully grown by an optical floating zone method.