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Cocatalysts (Pt or Pd) can significantly enhance the activity of photocatalysts. However, the electron transfer between cocatalysts and different kinds of functional groups have not been thoroughly studied. Here, a strategy of selectively anchoring cocatalysts (Pt or Pd nanoparticles (NPs)) on oxygen-doped carbon nitride (O-CN) was developed to optimize the electron transfer and enhance the photocatalytic activity. The oxygen functional groups are found to be beneficial to the loading of cocatalysts on the surface of O-CN. The adsorption energy (Eads) of Pd NPs on the N–C–O site is more negative than that on the C–O–C site, resulting in a favorable anchoring of Pd NPs on N–C–O, while the Eads of Pt NPs is lower on C–O–C than on N–C–O, leading to a preferential deposition of Pt on C–O–C. The O atom of N–C–O species, which possesses a lower value of isolated state than that of C–O–C species, shows a weaker electron-withdrawal property. So that the electrons can quickly transfer from O-CN to Pd than to Pt, leading to a higher hydrogen generation activity of O-CN/Pd than those of O-CN/Pt by photocatalytic water splitting. This is conducive to understand the interaction between the cocatalysts and O functional group on O-CN and the design of high-efficiency photocatalysts. [ABSTRACT FROM AUTHOR]

Introducing defect engineering into ZnO/ZnS heterojunction photocatalysts is an effective method to simultaneously improve their visible light performance and photocatalytic efficiency. Herein, a defect‐enriched ZnO/ZnS heterostructure photocatalyst was synthesized through a hydrozincite [Zn5(OH)6(CO3)2] intermediate‐deriving reaction. The mechanism analysis showed that there were interstitial Zn and Zn vacancies in the hydrozincite‐derived ZnO, while S vacancies and interstitial S and Zn vacancies were formed in ZnS components after calcination. These specific defect states endowed visible light response ability to both ZnO and ZnS components in the ZnO/ZnS photocatalysts. Under visible light irradiation, the photocatalytic hydrogen evolution rate of ZnO/ZnS reached 11.68 mmol h−1 g−1, and under simulated sunlight irradiation, the best photocatalytic hydrogen evolution rate could reach 27.94 mmol h−1 g−1, which was much higher than most previous reports. The analysis of energy band structure and photodeposition showed that the photocatalytic reduction sites were mainly on ZnS, and the photocatalytic reaction mainly followed the typical Z‐type mechanism. This work presents a simple and low‐cost method for the preparation of defects‐enriched ZnO/ZnS‐based photocatalytic materials with high photocatalytic activity and stability. [ABSTRACT FROM AUTHOR]

TiO2 has garnered a flourish of interest in the field of energy storage and energy conversion. Herein, a new generation of 3D Ni foam supported in situ grown 1D TiO2 nanoarray (Ni/TiO2) is successfully prepared, through an easy solution‐phase hydrothermal process, and then CdS nanorods branched Ni/TiO2 nanoarrays are fabricated (Ni/TiO2@CdS). Their formation parameters and growth mechanism are carefully studied. Both Ni/TiO2 and Ni/TiO2@CdS monolithic catalysts exhibit advantaged photocatalytic (PC) and photoelectrocatalytic (PEC) water splitting properties compared with that of most previously reported TiO2‐based film photocatalysts. Mechanism investigation reveals that both type II and Z‐scheme charge transport mechanisms coexist in Ni/TiO2@CdS sample, and an additional Z‐scheme charge transfer effect accelerates the photogenerated charge separation and transport efficiency. This study may open a new avenue for the utilization of TiO2‐based film catalysts in a broader field of energy and environmental catalysis areas. [ABSTRACT FROM AUTHOR]

The rational design and construction of cost‐effective nickel‐based phosphide or sulfide (photo)electrocatalysts for hydrogen production from water splitting has sparked a huge investigation surge in recent years. Whereas, nickel phosphides (NixPy) possess more than ten stoichiometric compositions with different crystalline. Constructing NixPy with well crystalline and revealing their intrinsic catalytic mechanism at atomic/molecular levels remains a great challenge. Herein, an easy‐to‐follow phase‐controllable phosphating strategy is first proposed to prepare well crystalline NixPy (Ni3P and Ni12P5) modified CdS@Ni3S2 heterojunction electrocatalysts. It is found that Ni3P modified CdS@Ni3S2 (CdS@Ni3S2/Ni3P) exhibits remarkable stability and bifunctional electrocatalytic activities in both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Density functional theory results suggest that P–Ni sites and P sites in CdS@Ni3S2/Ni3P, respectively, serve as OER and HER active sites during electrocatalytic water splitting processes. Moreover, benefiting from the advantageous photocatalyst@electrocatalyst core@shell structure, CdS@Ni3S2/Ni3P delivers an advantaged photoassisted electrocatalytic water splitting property. The champion electrical to hydrogen and solar to hydrogen energy conversion efficiencies of CdS@Ni3S2/Ni3P, respectively, reach 93.35% and 4.65%. This work will provide a general guidance for synergistically using solar energy and electric energy for large‐scale H2 production from water splitting. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) transition metal carbides and/or nitrides (MXenes) are a family of graphene-like 2D materials, with unique layered structures, high mechanical strength, excellent carrier mobility, and outstanding physical and chemical properties. In particular, the work function (Φ) of MXenes and Gibbs free energy of the adsorbed intermediate, such as H* (|△GH*|), can be regulated by their surface adsorption groups (–OH, –O, and –F), enabling the applications in the field of photocatalysis. This article systematically summarizes the recent advances of synthetic routes of MXene-based photocatalysts and discusses the interfacial charge kinetics and photogenerated charge transfer mechanism of MXene-based photocatalysts. Furthermore, major challenges and further research trends of MXene-based photocatalysts are also presented. [ABSTRACT FROM AUTHOR]

The incorporation of oxygenic groups could remarkably enhance the light absorption and charge separation of graphitic carbon nitride (g‐C3N4). The intrinsic role of oxygenic species on photocatalytic activity in g‐C3N4 has been intensively studied, but it is still not fully explored. Herein, the essential relationships between oxygenic functionalities and the catalytic performance are revealed. Results demonstrate that C−O−C functionality as an electron trap could help to increase the resistance of conduction transfer (Rct) by limiting electrons transfer in CNx. In contrast, N−C−O functionality between different tri‐s‐triazine unites could promote the electrons transfer, leading to a reduced Rct in CNx. The best H2 production rate (3.70 mmol h−1 g−1, 12.76‐fold higher than that of CN) is obtained over CN3, because of the highest N−C−O ratio (rN−C−O). The apparent quantum efficiency (AQE) of CN3 at 405 nm, 420 nm, 450 nm, 500 nm and 550 nm is 33.90 %, 20.88 %, 8.25 %, 3.66 % and 1.01 %, respectively. [ABSTRACT FROM AUTHOR]

To improve the photocorrosion of CdS nanorod arrays (CdS NRAs), we have designed a simple and facile treatment method of in-situ hydrogenation to fabricate CdS@SnS/SnO 2 heterostructure on fluorine-doped tin oxide glass, which is a highly photostable hydrogenated CdS-based film photocatalyst (CdS NRAs-H 2 ). Over a 25-h long time irradiation, the total photocatalytic hydrogen production of hydrogenated CdS NRAs is almost 2.0 times higher than that of un-hydrogenated CdS NRAs. Moreover, the average hydrogen production rate of CdS NRAs-H 2 can steadily maintain at 23.75 μmol cm −2 h −1 with 102% of retention rate after 5 reaction cycles, while they are only 6.13 μmol cm −2 h −1 with 30% of retention rate for un-hydrogenated common CdS NRAs. The photocatalytic mechanism on enhanced activity and stability for hydrogenated CdS NRAs photocatalyst is also investigated and discussed in detail. [ABSTRACT FROM AUTHOR]

Abstract: Boron and nitrogen codoped TiO2 nanorods (BNTRs) were synthesized via two-step hydrothermal reactions using TiN as a starting material. The as-prepared samples were characterized by X-ray diffraction, field-emission scanning electron microscope (SEM), transmission electron microscopy and X-ray photoelectron spectroscopy techniques. The results showed that TiO2 nanorods with the diameter of approximately 50–100nm and the length of several micrometers were doped by the interstitial N and B. The nanorods were firstly formed in the hydrothermal synthesis of nitrogen doped TiO2. The growing process of nanorods was observed by SEM and a most probable formation mechanism of the trititanate nanorods was proposed. The BNTRs showed a higher photocatalytic activity and a bigger photocurrent response than N–TiO2 nanorods under visible light irradiation. [Copyright &y& Elsevier]

Abstract: Nitrogen doped anatase TiO2 (N-TiO2) were prepared by hydrothermally treating TiN with H2O2. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), UV–vis diffuse reflectance spectrum (DRS), Fourier transform infrared spectra (FT-IR) and X-ray photoelectron spectroscopy (XPS) techniques. The results confirmed that the hydrothermal oxidation is an effective method to prepare N-doped TiO2 anatase. The nitrogen concentration in TiO2 could be controlled by the concentration of H2O2 solution. Photocatalytic degradation of methyl orange (MO) was carried out under visible light and UV–visible light irradiation, respectively. The as-prepared optimal N-TiO2 showed higher photocatalytic activity than N-P25 and P25, and exhibited excellent reusability. [Copyright &y& Elsevier]

Abstract: Ag nanoparticles loaded N-doped TiO2 nanotube arrays (Ag/N-TNTs) were successfully fabricated by an electrodeposition method. The Ag/N-TNTs were characterized using field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and UV–vis diffusion reflection spectroscopy (UV–vis DRS). The average photocurrent density and the photocatalytic degradation efficiency of the Ag/N-TNTs obtained for the degradation of Acid Orange II（AO-II）are 6 times and 6.8 times higher than those of annealed TiO2 nanotube arrays (A-TNTs), respectively. This bestows the Ag/N-TNTs as a promising photocatalytic material for organic pollutant degradation under visible light. [Copyright &y& Elsevier]

Abstract: B, N-codoped TiO2 nanotube arrays (BN-TNTs) were prepared in an electrolyte containing BF3 via an anodization process on a Ti sheet and subsequently annealed in ammonia ambient at 500 cu°C, and were characterized by the field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and UV–Vis diffusion reflection spectroscopy (DRS). The highly-ordered vertically oriented nanotube arrays were obtained. The BN-TNTs exhibited more excellent photoelectrochemical properties and photocatalytic activities than those of TiO2 nanotube arrays (TNTs), B-doped TiO2 nanotube arrays (B-TNTs) and N-doped TiO2 nanotube arrays (N-TNTs) under UV–visible and visible light. The synergistic effects of B and N codoping were proven by photocatalytic and photoelectrochemical performances. [Copyright &y& Elsevier]

Abstract: B,N-TiO2 photocatalysts were synthesized by boron doping firstly and subsequently nitrogen doping in NH3 at variable temperatures. The effects of the nitrogen doping temperature on the structure and photocatalytic activity of the B,N-codoped TiO2 were investigated. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectrum (DRS), electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity was evaluated with photocatalytic degradation of methyl orange dye (MO) under visible light and UV–visible light irradiation. The results suggested that the boron and nitrogen can be incorporated into the TiO2 lattice either interstitially or substitutionally or both, while the Ti–O–B–N structure plays a vital role in photocatalytic activity in visible light region. The optimal nitrogen doping temperature is 550°C. Higher temperature may form many oxygen vacancies and Ti3+ species, resulting in the decrease of photocatalytic activity in visible light. [ABSTRACT FROM AUTHOR]

Abstract: Cu2O/TiO2 nano–nano heterostructures with different concentrations of Cu2O were prepared by an alcohol-aqueous based chemical precipitation method, and were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy and UV–vis diffuse reflection absorption spectra. The photocatalytic efficiency of the Cu2O/TiO2 heterostructures was evaluated by degradation of Acid Orange II in water under UV–vis light and visible light irradiation. The results show that the heterostructures have dramatically improved photocatalytic activity comparing with pure TiO2 (P25). The prepared Cu2O/TiO2 heterostructures with the Cu2O concentrations of 30% and 70% have the best photocatalytic efficiencies, which are 6 times and 27 times higher than that of pure TiO2 (P25) under UV–vis light and visible light irradiation, respectively. [Copyright &y& Elsevier]

Abstract: Na x Ba y BiO3·nH2O (NBBO) has been prepared using a commercial NaBiO3·nH2O (NBO) as a starting material with a hydrothermal iron-exchange reaction. As-synthesized samples were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible light (UV–vis) absorbance spectra, thermogravimetry-differential scanning calorimetry (TG-DSC) and X-ray photoelectron spectroscopy (XPS) techniques. The photooxidation decomposition of phenol over NBBO has been carried out under visible-light irradiation (λ >400nm). The result revealed that the NBBO showed considerable photooxidation activity for phenol degradation in the range of visible light. The result of reusability indicated the structure of NBBO was instable, which was changed to Bi2O2CO3 in the photooxidation process, although photooxidation activity kept high in three runs. This study has provided useful information for the development of new bismuthate photocatalyst with higher photoactivity under visible-light irradiation. [Copyright &y& Elsevier]

Abstract: Cuprous oxide (Cu2O) nanoparticles and microparticles have been prepared by liquid phase chemical synthesis. The samples were characterized by means of SEM, XRD, UV/DRS and XPS. It was presented that as-prepared Cu2O nanoparticles are substantially stable in ambient atmosphere and the Cu+ as main state exists on the surface of Cu2O nanoparticles. As-prepared Cu2O microparticles can exist stably as a Cu2O/CuO core/shell structure; and the Cu2+ as main state exists on the surface of Cu2O microparticles. The behaviors of adsorption, photocatalysis and photocorrosion of Cu2O particles with different sizes were investigated in detail. The results show that Cu2O nanoparticles are very easy to photocorrosion during the photocatalytic reaction, which cannot be used as photocatalyst directly to degrade organic compound, although as-prepared Cu2O nanoparticles exhibit special property of adsorption. Cu2O microparticles have a higher photocatalytic activity than Cu2O nanoparticles because of its slower photocorrosion rate, although Cu2O microparticles have much lower adsorption capacity than Cu2O nanoparticles. The mechanisms of photocatalysis and photocorrosion for Cu2O under visible light were also discussed. [Copyright &y& Elsevier]

Abstract: Nitrogen-doped TiO2 (N-TiO2) nanoparticles have been successfully prepared via a direct and simple hydrothermal reaction of a commercial Degussa P25 with triethanol amine as solvent and nitrogen source. As-prepared N-TiO2 was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible light (UV–vis) absorption spectra, electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS) techniques. The results confirm that hydrothermal reaction is an effective way to incorporate nitrogen into the TiO2 lattice, especially nitrogen substitute for titanium. The nitrogen concentration in TiO2 can be as high as 21% (molar ratio), which is described as Ti1− y O2− x N x + y (in this paper, x=0.36, y=0.27, i.e., Ti0.73O1.64N0.63). The chemical statuses of N have been assigned to N–Ti–O and O–N–O in the TiO2 lattice as identified by XPS. Photocatalytic degradation of methyl orange has been carried out in both UV–vis (simulated solar light) and the visible region (λ>400nm). N-TiO2 exhibits higher activity than the Degussa P25 TiO2 photocatalyst, particularly under visible-light irradiation. This study has developed a promising and practical pathway to new nitrogen-doped photocatalysts. [Copyright &y& Elsevier]

Abstract: Both substitutional and interstitial nitrogen-doped titanium dioxides (N-TiO2) were prepared. Their surface states were clarified by XPS spectra of N 1s, O 1s and Ti 2p. The results of photocatalysis show that both substitutional and interstitial N impurities greatly enhance the photoactivity of TiO2 in visible light. Moreover, the visible light activity of interstitial N-doped TiO2 is higher than that of substitutional N-doped TiO2. The microwave synthesis presented in this paper is a promising and practical method to produce interstitial nitrogen-doped photocatalysts with high visible light activity. [Copyright &y& Elsevier]

Novel carbon nitride polymer sensitized TiO2nanotube arrays with high photocatalytic activity and photoelectrochemical response under visible light irradiation are prepared by electrodeposition. [ABSTRACT FROM AUTHOR]

Graphical abstract 2H- and 1T- mixed phase few-layer MoS 2 is prepared by a simple hydrothermal synthesis method for the first time. The designed MoS 2 @TiO 2 catalyst exhibits two times activity of Pt@TiO 2 for photocatalytic H 2 evolution, where the mixed phase MoS 2 as a co-catalyst shows the characteristic of 1 T-MoS 2 like Pt, rather than a semiconductor. Highlights • 1T-phase MoS 2 can be obtained by a facile hydrothermal method for the first time. • The MoS 2 @TiO 2 exhibits two times activity of Pt@TiO 2 for photocatalytic H 2 evolution. • The photo-generated electrons transfer path of MoS 2 @TiO 2 is clearly proven by KPFM. • The mixed phase MoS 2 apparently shows the characteristic of 1 T-MoS 2 like Pt. • MoS 2 here is as a superior to Pt co-catalyst rather than as a semiconductor. Abstract Recently, MoS 2 as an efficient co-catalyst has attracted much attention for photocatalytic water splitting. MoS 2 has two polymorphs: semiconducting phase (2H) and metallic phase (1T). The 2H- and 1T- MoS 2 show different reaction mechanism in photocatalytic H 2 evolution. However, so far, very few experiments have clearly evidenced the electron transfer process between TiO 2 and mixed phase MoS 2. This study for the first time has reported a simple hydrothermal synthesis method to prepare mixed phase few-layer MoS 2 nanosheets coated on TiO 2 nanorod arrays (MoS 2 @TiO 2) with a conductive fluorine-doped tin oxide (FTO) as a substrate. The structure of mixed phase MoS 2 was characterized carefully. The designed MoS 2 @TiO 2 exhibits two times higher activity than Pt@TiO 2 for photocatalytic H 2 evolution. The reliable conclusion that the photo-generated electrons from TiO 2 to MoS 2 nanosheets has clearly been evidenced by photoelectrochemical analyses and in-situ KPFM experiments, and the mixed phase MoS 2 here is a co-catalyst such like Pt rather than as a semiconductor. This study not only presents a series of solid experimental evidences to verify the electrons transfer process and photocatalytic mechanism, but also provides a new method in substituting MoS 2 for noble metal Pt as co-catalyst in high-efficiency photocatalytic water splitting into hydrogen. [ABSTRACT FROM AUTHOR]

Abstract: Nano-sized polyhedral crystalline Cu2O was evenly loaded throughout the structure of TiO2 nanotube arrays (TNTs) using an electrodeposition method, which resulted in a nanocomposite namely Cu2O/TNTs. The content of Cu2O loaded on the arrays was controlled by varying the electrodeposition charges. Under visible light, the photocurrent for water splitting and photocatalytic decolorization efficiency of dye Acid orange II (AO-II) of the Cu2O/TNTs obtained with the deposition charges of 500mC were about 35 and 18 times that of TNTs, respectively. The polyhedral Cu2O/TNTs would be a promising material for solar energy conversion and organic pollutant degradation. [Copyright &y& Elsevier]

A novel spherical N-CQDs/BiOI photocatalyst was successfully synthesized through a facile solvothermal method. The optimization experiments of hydrothermal time and temperature were carried out. The effect of ammonium citrate addition was investigated. The as-synthesized photocatalysts were characterized via X-ray diffraction, scanning and transmission electron microscopy, Fourier transform infrared spectrum and elemental analysis. The adsorption and photocatalytic performance of as-synthesized photocatalysts were studied, 0.2N-CQDs/BiOI showed the best performance. For the removal of anionic dye RhB, adsorption occupied a major position. The maximum adsorption capacity was 97.09 mg/g for RhB. For the removal of cationic dyes X3B, photocatalysis occupied a major position. The photocatalytic activity of 0.2N-CQDs/BiOI was superior to that of nano-TiO2 under the simulate sunlight irradiation. Different scavengers were used to analyze the effect of active species and photocatalytic degradation mechanism of X3B. The outstanding stability and performance make 0.2N-CQDs/BiOI has highly potential applications in wastewater treatment. [ABSTRACT FROM AUTHOR]

An efficient Ni 2 P–CdS photocatalyst for photocatalytic hydrogen evolution was synthesized by phosphorizing β-Ni(OH) 2 nanosheet with exposed (001) facets on CdS nanorods. The obtained Ni 2 P–CdS composite displays an outstanding and stable photocatalytic hydrogen generation rate of 68.47 mmol g−1 h−1 in 10 vol% lactic acid under visible light irradiation, more than 17 times higher than that for pure CdS nanorods. The transient photocurrent response, EIS measurement, Mott-Schottky plots, acidic LSV measurement, and PL spectra have proved that Ni 2 P loading can significantly improve the separation of photo-excited electron-hole pairs in CdS nanorods and enhance the hydrogen evolution capability for CdS. These improvements are achieved by features of Ni 2 P such as the high capability of trapping photo-generated electrons from CdS, lifting the total Fermi level and lowering the hydrogen evolution overpotential of the composite. The results show that β-Ni(OH) 2 precursor with a high exposure degree of (001) facet is contributed to the epitaxial formation of (001)-facet-exposed Ni 2 P co-catalyst on CdS nanorods, resulting in that the Fermi level and the hydrogen evolution overpotential of the composite can be further lifted and lowered. This study has provided a novel precursor-derived route to fabricate high-performance co-catalysts with highly exposed active facets on CdS nanorods for effective photocatalytic hydrogen evolution. • Ultrathin β-Ni(OH) 2 nanosheet precursor is employed in fabricating Ni 2 P on CdS. • β-Ni(OH) 2 nanosheet with exposed (001) facet facilitate Ni 2 P(001) growth on CdS. • Hydrogen evolution and charge separation of CdS can be markedly improved by Ni 2 P. [ABSTRACT FROM AUTHOR]

The substitution of noble metal platinum catalyst is one of the important research contents for sustainable development and is also the key to the practical application of photoelectrochemical (PEC) hydrogen production. In this work, we loaded the 1T-2H mixed phase MoS 2 on the hydrogenated anatase/rutile heterophase TiO 2 (A-H-RTNA) by hydrothermal method to prepare a new MoS 2 /A-H-RTNA electrode material. The prepared material exhibited higher carrier density, lower PL intensity and higher conductivity than Pt/A-H-RTNA because 1T-MoS 2 has more active sites and lower charge transfer resistance than Pt. With the bias voltage of −0.4 V, the optimized 16MoS 2 /A-H-RTNA as photocathode shows the largest PEC hydrogen production rate of 1840 mmol m−2 h−1, which is 2.9 and 2.2 times higher than those of A-H-RTNA (625 mmol m−2 h−1) and Pt/A-H-RTNA (848 mmol m−2 h−1), respectively. We innovatively used the prepared 16MoS 2 /A-H-RTNA film as counter electrode instead of Pt electrode to construct a PEC system without any noble-metal. The result demonstrates that the noble-metal-free MoS 2 loaded on TiO 2 electrode as counter electrode has 75% PEC activity of noble metal Pt electrode. This study develops a PEC method for hydrogen evolution, which no longer depends on precious metal platinum as cathode. A new MoS 2 /A-H-RTNA electrode with 2 times higher hydrogen production rate than Pt/A-H-RTNA was prepared by loading MoS 2 on the hydrogenated TiO 2 heterostructure film. The prepared MoS 2 /A-H-RTNA film was used as photocathode instead of Pt electrode to construct an innovative and efficient PEC system without any noble-metal. Image 1 • MoS 2 is loaded on hydrogenated anatase/rutile TiO 2 heterophase structure (A-H-RTNA). • MoS 2 /A-H-RTNA has low charge transfer resistance for photoelectrochemical (PEC) reaction. • MoS 2 /A-H-RTNA as photocathode has 2 times higher PEC hydrogen production rate than Pt/A-H-RTNA. • MoS 2 /A-H-RTNA film can be used as photocathode instead of Pt electrode. • An innovative and efficient PEC system without any noble metal is constructed. [ABSTRACT FROM AUTHOR]

A facile method of loading CoS x nanosheet onto CdS nanorod has been designed, and the prepared CdS-CoS x composite catalyst exhibited significantly improved performance for photocatalytic hydrogen evolution compared with CdS catalyst. This composite catalyst was also used as a photoanode for photoelectrochemical (PEC) hydrogen production. The hydrogen production rate reached 168.6 μmol cm−2 h−1 (37.77 L m−2 h−1) under the simulated solar light, which is 2.7 times that of CdS and the same as that of CdS–Pt. In addition, in the Na 2 S–Na 2 SO 3 system for PEC hydrogen production, an abnormal relationship between photocurrent and the hydrogen production yield was found. By designing a series of experiments, the photocatalytic and photoelectrochemical characteristics for hydrogen production were reasonably revealed for the first time. In this work, the prepared structured catalyst is easy to be recycled, and CoS x can replace precious metal Pt, showing a promising application. Image 1 • CoS x as co-catalyst is loaded on CdS nanorod by a facile method. • CdS-CoS x has good activity and stability for photoelectrochemical (PEC) reaction. • PEC activity of CdS-CoS x as photoanode for H 2 production is the same as that of CdS–Pt. • An abnormal relationship between photocurrent and hydrogen production is found. • The reaction network in Na 2 S–Na 2 SO 3 system for PEC H 2 production is proposed. [ABSTRACT FROM AUTHOR]

The active sites of nitrogen-defected carbon nitride with high efficiency for photocatalytic H 2 production are revealed. • g-C 3 N 4 with abundant N-defects (CNx) is synthesized by the HNO 3 modification. • CNx shows 19 times higher activity than g-C 3 N 4 for photocatalytic H 2 evolution. • CNx has an excellent stability for photocatalytic H 2 evolution. • The surface functional groups and the N defects impact the catalytic efficiency significantly. • The active-site structure diagram of CNx for photocatalysis is revealed. The deficient carbon nitride (g-C 3 N 4) displays not only an improved visible light absorption, but also an enhanced photocurrent and restricted electron-hole pair recombination. In this work, nitric acid was used to engineer the defects in g-C 3 N 4 , which simultaneously possessed fibrous and layered structures. The modified g-C 3 N 4 (CNx) was utilized as photocatalyst for the effective photocatalytic H 2 evolution. As high as 1160 μmol/h/g H 2 production rate (λ > 400 nm) was achieved over CN3, 19 times higher than that of pristine g-C 3 N 4 (CN0, 60 μmol/h/g). The apparent quantum efficiencies (AQE) of CN3 at 405 and 420 nm were 7.83% and 7.67%, respectively. The mechanism study showed that the surface functionality and the N defects impacted the catalytic efficiency significantly. The O C, NH x species and N defects at N 2C site acted as the active sites for the photocatalytic hydrogen evolution, while the OH group displayed the negative effect in this process. To the best of our knowledge, the active-site structure diagram of the nitrogen-defected CNx for photocatalysis was shown systematically. Additionally, this nitrogen-defected CNx demonstrated a high stability for photocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]

Graphical abstract Oxygen vacancy on CuBi 2 O 4 and interfacial electric field between Bi 2 WO 6 and CuBi 2 O 4 are introduced via a solvothermal process, facilitating the formation of Z-scheme heterojunction for high photocatalytic degradation efficiency for tetracycline. Highlights • A solvothermal process is proposed to design Bi 2 WO 6 /CuBi 2 O 4 Z-scheme heterojunction. • Bi 2 WO 6 /CuBi 2 O 4 shows high activity for visible-light degradation of tetracycline. • Surface oxygen vacancy is introduced to increase the generation of O 2 −. • Interfacial electric field is formed to promote charge injection from Bi 2 WO 6 to CuBi 2 O 4. • Interfacial charge migration at heterojunction has facilitated the electric field formation. Abstract In order for the removal of Tetracycline (TC) in wastewaters, an efficient binary Bi 2 WO 6 /CuBi 2 O 4 Z-scheme heterojunction photocatalyst was synthesized by loading Bi 2 WO 6 (BWO) nanoparticles on CuBi 2 O 4 (CBO) nanorods via a solvothermal route. The obtained Bi 2 WO 6 /CuBi 2 O 4 composite displays photocatalytic activity for TC degradation more than five times higher than that for pure CBO nanorods. The recycling experiment shows that over 91% of TC can be photo-degraded by the optimal Bi 2 WO 6 /CuBi 2 O 4 photocatalyst within 60 min even after four cycles. Results of SEM, transient photocurrent response, EIS measurement prove that solvothermal process for BWO loading can introduce rough surface with high-density negative charge on CBO, contributing to effective photo-induced carrier transfer. XPS, Mott–Schottky plots and PL spectra reveal that the loading of BWO as well as interfacial charge redistribution can induce the formation of interfacial electric field for Z-scheme heterojunction, contributing to the high oxidation and reduction capabilities ability of Bi 2 WO 6 /CuBi 2 O 4 composite. The study on photocatalytic mechanism discloses that hole (h+) and superoxide radical (O 2 −) are dominating reactive oxidation species (ROS) in the photodegradation process. This study has provided a novel route to fabricate Z-scheme photocatalysts for effective photocatalytic degradation processes. [ABSTRACT FROM AUTHOR]

Photocatalytic water splitting into hydrogen is a very attractive and desirable technology to realize sustainable and renewable green energy conversion. Up to now, many research results have confirmed that cocatalyst such as Pt is essential for a high efficiency photocatalytic H 2 evolution system. In a traditional view, the cocatalyst should be closely combined with the photocatalyst to achieve a high H 2 or O 2 photo-productive rate. In this work, an unusual point has been put forward that the suitable loading position of cocatalyst Pt for film-type TiO 2 catalyst is on the bare Fluorine-doped tin oxide (FTO) substrate instead of on the surface of TiO 2 in the electrolyte solutions. Especially, in acidic electrolyte, the hydrogen production rate of this new designed catalyst with Pt loaded on FTO (TiO 2 -Pt/FTO) reaches 2.4 times that of the common catalyst with Pt loaded on TiO 2 (Pt/TiO 2 -FTO). According to the experiment results, it is supposed that this loading way of cocatalyst on the substrate can construct a self-bias photocatalytic electrochemical cell system, drive electrolyte ions' movement directionally, and obtain high photocatalytic H 2 production efficiency. The universality of this innovation has been verified by CdS and CdS@TiO 2 film-type catalysts. This study provides a new guide in exploring high-efficiency film-type photocatalytic system for water splitting into hydrogen in the electrolyte solution. [ABSTRACT FROM AUTHOR]

CuO 1− x cluster-modified TiO 2 (CuO 1− x /TiO 2 ) photocatalysts were prepared by an in-situ photoreduction deposition of Cu on TiO 2 powder support using copper acetate as a Cu source. The prepared samples without any Pt co-catalyst present an especially high photocatalytic H 2 -evolution activity under solar light irradiation with 5% glycerol as sacrificial agent. The optimal CuO 1− x /TiO 2 catalyst with only 1 wt% CuO 1− x exhibits a high activity of 1725 μmol h −1 g −1 for H 2 evolution, which reaches 120 times that of TiO 2 . The high photocatalytic activity of H 2 production is attributed to the highly dispersed CuO 1− x nano clusters on the surface of the TiO 2 . In addition, Pt/CuO 1− x /TiO 2 was also prepared by loading Pt on CuO 1− x /TiO 2 sample, and its photocatalytic hydrogen evolution activity is enhanced 1.8 times compared with that of Pt/TiO 2 for overall water splitting reaction under solar light, demonstrating that a small amount CuO 1− x wondrously improves the photocatalytic activity of Pt/TiO 2 for overall water splitting reaction. This paper reports an economic and simple approach to prepare a photocatalyst with high hydrogen-production activity. [ABSTRACT FROM AUTHOR]

The rational design of interface is a key factor for improving the performance of photocatalysts. Herein, a nanocomposite comprised of Ti 3+ doped rutile TiO 2 octahedrons exposing active (111) facets and two-dimensional Ti 3 C 2 sheets was synthesized by a hydrothermal oxidation route and subsequent hydrazine hydrate reduction. The crystallographic facet proportions of TiO 2 can be controlled by NH 4 F as a facet controlling agent. The photocatalytic activity of the TiO 2 /Ti 3 C 2 composite was maximized by completely exposing the active (111) surfaces. The interfacial microstructure between Ti 3 C 2 and TiO 2 can be tuned by the hydrothermal reaction duration. The charge kinetics was substantially steered by the hole trapping effect of 2D Ti 3 C 2 terminated by OH groups. Through the reduction by hydrazine hydrate, Ti 3+ was doped into the bulk of TiO 2 , thereby enabling the photocatalytic activity under visible light. This work opens a new window to the rational design of photocatalysts based on 2D MXene materials. [ABSTRACT FROM AUTHOR]

In recent years, tremendous efforts have been devoted to develop new photocatalyst with wide spectrum response for H 2 generation from water or aqueous solution. In this work, CdS nanoparticles (NPs) have been immobilized on hydrogenated three-dimensional (3D) branched TiO 2 nanorod arrays, resulting in a highly efficient photocatalyst, i.e, CdS/H-3D-TiO 2 . In addition, electrochemical reduction of H + ion is identified as a limiting step in the photocatalytic generation of H 2 at this catalyst, while here a Pt wired photocatalysis system (CdS/H-3D-TiO 2 /Pt-wire) is designed to overcome this barrier. Without the application of potential bias, visible light photocatalytic hydrogen production rate of CdS/H-3D-TiO 2 /Pt-wire is 18.42 μmol cm −2 h −1 , which is 11.2 times that of CdS/H-3D-TiO 2 without Pt (1.64 μmol cm −2 h −1 ). The Pt wire acts as an electron super highway between the FTO substrate and H + ions to evacuate the generated electrons to H + ions and catalyze the reduction reaction and consequently generate H 2 gas. This work successfully offers a novel direction for dramatic improvement in H 2 generation efficiency in photocatalysis field. [ABSTRACT FROM AUTHOR]

Two kinds of branched hydrogenated TiO 2 nanorod arrays, i.e., hydrogenated TiO 2 nanorod supported hydrogenated TiO 2 branch arrays (H-BTNRs) and hydrogenated TiO 2 nanorod supported unhydrogenated TiO 2 branch arrays (B/H-TNRs), have been successfully designed and prepared by a facile approach. Under simulated solar light, the prepared B/H-TNRs have the highest hydrogen evolution rate of 6.65 μmol cm −2 h −1 , which is 4.7 and 2.4 times those of hydrogenated TiO 2 nanorod arrays (H-TNRs) and H-BTNRs, respectively. This study indicates that the heterostructure design of the unhydrogenated TiO 2 branch and hydrogenated TiO 2 nanorod promotes the separation of charge carries on the interface and enhances photocatalytic hydrogen evolution. [ABSTRACT FROM AUTHOR]

Non-noble metals are attractive alternatives to Pt co-catalysts for hydrogen production. Herein, Co nanoparticles were designed to uniformly deposit on the surface of TiO 2 nanotube arrays (Co/TNAs) via photo-deposition and reduction method. The structure and optical property of the Co/TNAs were characterized. Compared with pure TNAs, Co/TNAs showed a highly photocatalytic activity for hydrogen production without the Pt co-catalyst under UV–vis light irradiation. The study presents a promising practical way using non-noble metal as co-catalyst for photocatalytic splitting of water into hydrogen. [ABSTRACT FROM AUTHOR]

The hierarchical Ag NPs with a bimodal size distribution were auto-decorated on the surface of rice-like N-TiO 2 (named h-Ag/N-TiO 2 ) by semiconductor-metal double excitation process under solar light irradiation. The photoinduced growth process of self-assembled h-Ag/N-TiO 2 and its photocatalytic mechanism of photo-splitting ethanol into hydrogen have been discussed in detail. The synthesized h-Ag/N-TiO 2 as a plasmonic photocatalyst for photo-splitting ethanol exhibited a higher hydrogen production rate (4.7 mmol h −1 g −1 ) than Ag NPs universally loaded N-TiO 2 (3.4 mmol h −1 g −1 ) and pure N-TiO 2 (2.1 mmol h −1 g −1 ). This work presents a reversed photo-induced synthesis strategy to design a stable Ag-TiO 2 plasmonic photocatalyst with high photocatalytic efficiency under solar light. A better understanding of this solar light induced self-assembled process for Ag-TiO 2 is crucial in developing metal-semiconductor system for solar energy materials. [ABSTRACT FROM AUTHOR]

Uniformly dispersed Ag nanoparticles (NPs) were successfully loaded on both the outer and inner surface of the TiO 2 nanotube arrays (NTs) through a simple polyol method. The as-prepared Ag/TiO 2 -NTs were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV–vis diffusion reflectance spectroscopy. Photoelectrochemical behaviors were investigated via photocurrent response and electrochemical impedance spectroscopy (EIS). Photocatalytic activity of Ag/TiO 2 -NTs was evaluated by degradation of acid orange II under visible light irradiation. The results showed that photocatalytic efficiency of Ag/TiO 2 -NTs is more than 5 times higher than that of pure TiO 2 NTs. Comparing with the electrochemical deposition method, the photocatalytic activity of Ag/TiO 2 -NTs prepared by polyol method has been obviously increased. [ABSTRACT FROM AUTHOR]

Highlights: [•] The coupled Cu2O with g-C3N4 of narrow-band-gap semiconductor has been designed. [•] g-C3N4/Cu2O is prepared via an alcohol-aqueous based on chemical precipitation method. [•] g-C3N4/Cu2O exhibits the enhanced photocatalytic activity under visible-light. [•] The enhanced photocatalytic activity is proven by the transient photocurrent test. [•] A mechanism for the visible-light-driven photocatalysis of g-C3N4/Cu2O is revealed. [Copyright &y& Elsevier]

Abstract: The influence of the electrodeposition potential on the morphology of Cu2O/TiO2 nanotube arrays (Cu2O/TNA) and their visible-light-driven photocatalytic activity for hydrogen evolution have been investigated for the first time in this work. The photocatalytic hydrogen evolution rate of the as-prepared Cu2O/TNA at the deposition potential of −0.8 V was about 42.4 times that of the pure TNA under visible light irradiation. This work demonstrated a feasible and simple electrodeposition method to fabricate an effective and recyclable visible-light-driven photocatalyst for hydrogen evolution. [Copyright &y& Elsevier]

Abstract: Cu(OH)2/TNAs photocatalyst was prepared by loading Cu(OH)2 nanoparticles on TiO2 nanotube arrays (TNAs) using a chemical bath deposition method. The amount of Cu(OH)2 loaded on the arrays was controlled by the repeated deposition times. The prepared catalyst was used to generate hydrogen under simulated solar light irradiation, and the results demonstrated that the hydrogen yield of Cu(OH)2/TNAs was 20.3 times that of the pure TNAs. Furthermore, the photocatalytic efficiency for hydrogen production decreased only 5.8% after five cycles, indicating that Cu(OH)2/TNAs photocatalyst showed excellent stability and reusability. This work presents an applicable and facile method to fabricate a highly active and stable photocatalyst for hydrogen production. [Copyright &y& Elsevier]

Abstract: A facile approach for the preparation of Fe3O4/g-C3N4 nanospheres with good porous structure has been demonstrated by a hydrothermal method. The as-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible light (UV–vis) absorbance spectra and X-ray photoelectron spectroscopy (XPS). The photocatalytic decomposition of methyl orange (MO) by the as-prepared samples was carried out under visible light irradiation. The reusability and magnetic properties were also investigated. The results revealed that the porous Fe3O4/g-C3N4 nanospheres showed considerable photocatalytic activity, and exhibited excellent reusability and magnetic properties with almost no change after five runs. [Copyright &y& Elsevier]

Abstract: Boron and phosphor co-doped TiO2 nanotube arrays (BP–TNTs) were prepared in an electrolyte containing triethyl borate and tributyl phosphate via an anodization process on a Ti sheet, and were characterized by the field-emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV–Vis diffusion reflectance spectroscopy. The photoelectrochemical properties and photocatalytic activities of obtained-samples were tested under visible light irradiation. The results showed that the photoelectrochemical and photocatalytic activities of B–TNTs, P–TNTs and BP–TNTs were higher than those of pure TiO2 nanotube arrays (TNTs). The synergistic effect of B and P co-doping was absent. [Copyright &y& Elsevier]

Abstract: Hierarchically structured TiO2 (HST) films composed of top porous nanoparticle layer and underneath nanotube array layer are obtained by an anodization method on fluorine doped tin oxide surfaces. Compared with the TiO2 nanotube arrays photoanode on Ti substrate, the HST photoanode exhibits a higher photoelectrocatalytic activity towards the oxidation of water and organics (e.g., glucose). [Copyright &y& Elsevier]

Ultrathin Bi 2 WO 6 nanosheet with hydrophobic and nonpolar surface boosts both the mass-transfer and adsorption of CO 2 , resulting in a high-efficiency photocatalytic conversion of CO 2 in H 2 O vapor. • Bi 2 WO 6 with ultrathin structure with hydrophobic and nonpolar surface is successfully prepared. • This ultrathin nanosheet displays 3.2-fold higher CO 2 adsorption amount than that of bulk. • This special structure endows a high-efficiency photocatalytic CO 2 conversion in H 2 O vapor without co-catalyst. • The photocatalytic CO 2 reduction mechanism is revealed by the in-situ DRIFTS. The artificial carbon dioxide (CO 2) photoreduction into useful chemicals utilizing solar energy demands the stable photocatalysts with high-efficiency charge separation and effective CO 2 adsorption capacity. For all this, for the first time, Bi 2 WO 6 photocatalysts with atomically thin structure along with hydrophobic and nonpolar surface are successfully designed and prepared using CTAB as assistant. The ultrathin feature with short diffusion distance significantly facilitates the charge separation. The hydrophobic surface, modified by nonpolar long carbon chains of CTA+, boosts both the mass-transfer and adsorption of CO 2 , meanwhile suppressing the H 2 O adsorption. Hence, the prepared photocatalyst exhibits a high-efficiency photocatalytic conversion of CO 2 in H 2 O vapor without co-catalyst due to high CO 2 concentration and sufficient photogenerated carriers. The photocatalytic mechanisms including adsorption concentration and activation process of CO 2 are further revealed by the in-situ diffuse reflectance infrared fourier transform spectra (DRIFTS). As a new feature, linearly adsorbed CO at 2035 cm−1 is found on hydrophobic surface of Bi 2 WO 6 , and the absorbance of CO is critical to the next reaction step for CH 4 generation. This innovation provides a facile avenue for the design of photocatalysts with remarkable CO 2 capture ability to achieve the practical application of photocatalytic CO 2 reduction. [ABSTRACT FROM AUTHOR]

• The density functional theory calculations reveal highly active phase structure of MoSe 2. • A volcano-like correlation of MoSe 2 structure and photocatalytic activity is presented. • The mixed phase MoSe 2 is prepared controllably as an excellent cocatalyst for H 2 production. • The photogenerated electron-hole transfer mechanism is confirmed. It is still of great practical significance to exploring low-cost and earth-abundant alternative materials as cocatalyst for photocatalytic hydrogen evolution. The density functional theory (DFT) calculations indicated that both the basal plane and the edge of mixed phase MoSe 2 provide the highly catalytic activity for hydrogen evolution reaction (HER). Based on this, the mixed phase MoSe 2 was designed as an excellent cocatalyst because of superior ability to receive electrons and optimal active sites for HER. Herein, the ternary (1T/2H) MoSe 2 /CdS-CdSe structure was prepared by a simple hydrothermal method. The hydrazine monohydrate as reductant helps to control 1T phase content of MoSe 2 , and the maximum content of 1T phase MoSe 2 reaches 66.5%. The results showed that the H 2 evolution rate of the optimized MoSe 2 /CdS-CdSe reached a value of 24.34 mmol h−1 g−1 and a high quantum efficiency (QE) of 28.5% at 500 nm. A volcano-like correlation has been presented for the first time to illustrate the effect of structures of MoSe 2 on photocatalytic activity for HER, which provides the direction of design of MoSe 2 cocatalyst. [ABSTRACT FROM AUTHOR]