Insights into morphology-dependent Au/TiO2catalyst in glycerol aqueous solutions towards photothermal reforming hydrogen production

Probing the effect of spatial morphology of catalyst on its photothermal catalytic performance is crucial for solar-driven renewable catalytic reforming of hydrogen production. In this study, Au nanoparticles loaded on various morphologies of TiO₂ nanoparticles were synthesized and characterized. The experimental results indicated that decorating TiO₂ with Au nanoparticles could dramatically increase its photocatalytic activities by 20–40 times. The photothermal conversion efficiency of Au/TiO₂ (12.74%–25.54%) was higher than those of TiO₂ due to the introduction of LSPR of Au nanoparticles could effectively improve the utilization of solar spectrum. Titania nanoflower (TNF) nanoparticles with high light absorption capacity, better colloidal dispersion stability, porous properties and narrow band gap represented the highest H₂ productivity (144.13 μmol·g⁻¹·h⁻¹). The coarse surface structure was also conducive to the dispersion of gold particles on the surface of the carrier and the growth rate of Au/TNF hydrogen production (40 times) which was higher than that of other morphology within 2 h. The results of glycerol photothermal hydrogen generation highlighted the effect of temperature on colloidal dispersion stability and hydrogen production capability of nanoparticle suspension. It demonstrated that the photothermal effect aroused a temperature rise that would deteriorate the dispersion stability of the suspension although a local entropy increase in the catalyst nanoparticles might occur. At the same time, the temperature rise caused by the photothermal effect efficiently produces hydrogen in the reaction temperature range. Therefore, an ideal temperature setting for maximal hydrogen generation could be validated and improved the photothermal synergistic impact on biomass-reformed hydrogen generation.     

Highly efficient photocatalytic hydrogen evolution by using Rh as co-catalyst in the Cu/TiO2 system

Cu/TiO₂ was modified by adding Rh as co-catalyst and used as a highly efficient photocatalyst for the hydrogen evolution reaction. A low amount of Rh was loaded onto Cu/TiO₂ by the deposition-precipitation with urea (DPU) method to observe the effect on the hydrogen production displayed by different samples. The Rh–Cu/TiO₂ oxide structure exhibited a remarkably high photocatalytic hydrogen evolution performance, which was about twofold higher than that of the Cu/TiO₂ monometallic photocatalyst. This outstanding performance was due to the efficient charge carrier transfer as well as to the delayed electron-hole recombination rate caused by the addition of Rh. The influence of the different parameters of the photocatalyst synthesis and reaction conditions on the photocatalytic activity was investigated in detail. Hydrogen evolution was studied using methanol, ethanol, 2-propanol and butanol as scavengers with an alcohol:water ratio of 20:80. The methanol-water system, which showed the highest hydrogen production, was studied under 254, 365 and 450 nm irradiation; Rh–Cu/TiO₂ showed high photocatalytic activity with H₂ production rates of 9260, 5500, and 1940 μmol h^?1 g^?1, respectively. The Cu–Rh/TiO₂ photocatalyst was active under visible light irritation due to its strong light absorption in the visible region, low band gap value and ability to reduce the electron (e^?) and hole (h⁺) recombination.     

Investigation on multifunctional Au/TiO2@n-octadecane microcapsules towards catalytic photoreforming hydrogen production and photothermal conversion

Combining solar energy utilization and hydrogen production is an ideal model for renewable energy development. Especially the conversion of broad-spectrum solar energy into chemical energy of hydrogen and thermal energy can enrich solar energy storage methods. Herein, novel multifunctional Au/TiO₂@n-octadecane microcapsules with core-shell structure were design and synthesized by wet chemical reduction and electrostatic adsorption self-assembly methods for photothermal hydrogen production and thermal storage. The results showed that microencapsulation of photothermal catalysts could provide an effective reaction area and excellent dispersion stability, where hydrogen production and light to hydrogen efficiency were increased in the 43% and 0.3% respectively, compared to the nanoparticle suspension system. Based on the recorded temperature variations caused by the photothermal effect, the calculated photothermal conversion efficiency and specific absorption rate of Au/TiO₂@n-octadecane was 25.01% and 277% higher than that of Au/TiO₂ suspension. The proposed hydrogen production and thermal storage method via multifunctional microcapsules might shed some light on the study of improving full-spectrum energy conversion efficiency of solar energy.     

CuO-TiO2 nanostructures prepared by chemical and electrochemical methods as photo electrode for hydrogen production

In present study, copper (II) oxide (CuO) nanostructures were separately synthesized via chemical and electrochemical methods. CuO were coated with chemically synthesized titanium dioxide (TiO₂). Morphological and structural properties of CuO and TiO₂ coated CuO (CuO-TiO₂) materials were examined via field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). FESEM images showed that nanowire like CuO formed at both chemical and electrochemical techniques. TiO₂ nanoparticles were homogenously distributed all over CuO surfaces. XRD pattern revealed CuO has monoclinic crystal structure with metallic Cu. Moreover, rutile TiO₂ crystallized in the tetragonal crystal structure. Electrochemical impedance spectroscopy (EIS) and potentiodynamic (PD) polarization measurements were utilized to study electro catalytic performance of the materials towards hydrogen evolution reaction (HER). The values of both energy consumption, and energy efficiency were determined as 329.43 kJ mol^?1 and 86.0% at ?50 mA cm^?2 current density for HER on electrochemically synthesized CuO-TiO₂ at 25 °C.     

Investigation on the effect of temperature on photothermal glycerol reforming hydrogen production over Ag/TiO2 nanoflake catalyst

Photothermal reforming of biomass-derived hydrocarbons is an efficient approach to generate renewable hydrogen driven by solar. However, the current understanding of the general thermal effect on hydrogen production is limited since the photothermal and thermal radiation from solar is difficult to separate. Herein, an experimental study is carried out by synthesizing a series of photothermal catalysts composed of Ag nanoparticles supported on TiO₂ nanoflake (TNF). The structure of the Ag/TNF was examined by XRD, XPS, and HRTEM, respectively. The local temperature rise of the Ag/TNF was detected during the photothermal reforming reaction of the aqueous bio-glycerol, and its influence on H₂ yield was analyzed. By introducing different weight ratios of Ag nanoparticles on TNF, the equilibrium temperature was obviously increased due to the localized surface plasmon resonance (LSPR) effect and dynamic balance between LSPR and heat dissipation was found. It was observed that increasing the weight ratio of Ag particles could result in an increased temperature and lower hydrogen yields. In fact, such photothermal reforming hydrogen production was a synergistic effect between photogenerated-electrons and phonons. Therefore, precisely regulating the photothermal effect by controlling the metal nanoparticles loading to achieve proper thermal balance and high catalytic activity is one effective countermeasure to enhance hydrogen production.     

Structural properties of CuO/TiO2 nanorod in relation to their catalytic activity for simultaneous hydrogen production under solar light

CuO was introduced into porous TiO₂ nanorod through impregnation method. Before the impregnation step, TiO₂ nanorod was hydrothermally synthesized from TiO₂ powder in aqueous NaOH solution and followed by thermal treatment at 450 °C. The structures and properties of impregnated samples were characterized using various techniques, including XRD, BET, XAS, TEM, and UV-DRS. Their photocatalytic performance on simultaneous hydrogen production from pure water and aqueous methanol solution was also investigated under solar light. It was found that CuO/TiO₂ nanorod possessed a high surface area, good photocatalytic property and excellent hydrogen generation activity. Incorporation of Cu ions into the lattice framework of anatase TiO₂ nanorod enhanced the efficiency in visible region at 438–730 nm. Moreover, the XAS results showed that some Cu ions formed solid solution in the TiO₂ nanorod (Cu_xT_1−xO₂). However, the excessive incorporation of Cu ions did not improve any ability of anatase TiO₂ nanorod for production of hydrogen from pure water splitting. This could be due to the excessive CuO agglomeration at outside-pores which blocked the sensitization of TiO₂ nanorod. Only 1% Cu/TiO₂ nanorod was found to be a remarkable and an efficient photocatalyst for hydrogen production under solar light from both pure water and sacrificial methanol splitting. The highest rate of hydrogen production of 139.03 μmol h⁻¹ g_catalyst⁻¹ was found in sacrificial methanol which was 3.24% higher than in pure water.     

Facile construction of self-assembled Cu@polyaniline nanocomposite as an efficient noble-metal free cocatalyst for boosting photocatalytic hydrogen production

Photocatalytic Hydrogen production via water splitting is considered a sustainable ecofriendly pathway to replenish the current and future energy demands. In this study, the self-assembly synthesis of Cu nanospheres (～8 nm) surrounded by a thin conductive layer of polyaniline (Cu@PANI) was rationally engineered via in?situ polymerization. Afterward, it was successfully deposited onto the TiO₂ surface to improve the photocatalytic activities for hydrogen production. The optimal Cu@PANI/TiO₂ ternary photocatalyst produced a substantial hydrogen generation rate (HGR) of 17.7 mmol h^?1 g^?1, 207-fold higher than that of bare TiO₂. The performance was considerably improved compared with (Cu–TiO₂)/PANI and (PANI-TiO₂)/Cu composites prepared by changing the deposition sequence of Cu and PANI. Such an improved activity was because of multiple transferring paths of photogenerated electrons in the composite. Interestingly, the as-prepared ternary photocatalyst exhibited superior hydrogen evolution compared with the binary hybrids (Cu/TiO₂ and PANI/TiO₂). The exceptional performance of Cu@PANI/TiO₂ could be understood considering the distinctive electrical conductivity of PANI and heterojunction formed between PANI and TiO₂, as well as the merits of the Schottky junction constructed between Cu and PANI. These superior features could efficiently suppress the recombination rate of the photogenerated electron–hole pairs and maximize the photocatalytic activity. This study provides new insights for understanding the effect of electron transfer pathways on photocatalytic activities.     

Precursor self-derived Cu@TiO2 hybrid Schottky junction for enhanced solar-to-hydrogen evolution

Solar-to-hydrogen production has attracted increasing attention since it possesses great potential in alleviating energy and environmental crises to some extent. The key issue is to develop efficient photocatalysts exhibiting superior hydrogen production capability. In this work, Cu@TiO₂ hybrid (Cu nanoparticles encapsulated in TiO₂) has been successfully prepared by Cu₂O self-template reduction through solvothermal treatment in ethylene glycol-water mixed solvent. When octahedral Cu₂O is involved in the reaction system, the Cu₂O@Ti-precursor octahedral structure is first formed and subsequently the Cu@TiO₂ hybrid is prepared with the reduction of ethylene glycol (EG). The Cu@TiO₂ hybrid derived with different mass of Cu exhibits improved photocatalytic hydrogen production performance compare to pure TiO₂ and P25. Among those photocatalysts, the Cu@TiO₂-10% (the copper content is 10 wt%) shows the highest hydrogen evolution rate of 4336.7 μmol g^?1 h^?1, and it is twice as much as the pure TiO₂ and 1.9 times as much as P25, respectively. Based on the photo/electrochemical results, an efficient photo-generated electron-hole separation contributes to the enhancement of photocatalytic H₂ evolution upon the Cu@TiO₂ hybrid. When replacing octahedral Cu₂O with cubic and truncated octahedrons ones, the Cu@TiO₂ hybrid photocatalysts are also obtained and they also display superior solar-to-hydrogen evolution than pure TiO₂ and P25. It is expected this work could develop an approach to design Cu-encapsulated hybrid photocatalysts for hydrogen generation.     

Cu2O/Cu/TiO2 nanotube Ohmic heterojunction arrays with enhanced photocatalytic hydrogen production activity

Cu₂O/Cu/TiO₂ nanotube heterojunction arrays were prepared by assembling Cu@Cu₂O core-shell nanoparticles on TiO₂ nanotube arrays (NTAs) using a facile impregnation-reduction method. SEM and TEM results show that Cu@Cu₂O plate-like nanoparticles with tens of nanometers in size are confined inside TiO₂ NTAs. Only the outmost several nanometers of the nanoparticles are Cu₂O and the predominant inner of the nanoparticles are Cu metals. Cu L₃VV Auger spectra of Cu₂O/Cu/TiO₂ NTAs suggest that Cu metals are enveloped by at least several nanometers Cu₂O on the surface, which further confirms the Cu@Cu₂O core shell structure of Cu nanoparticles. The ability of light absorption of Cu₂O/Cu/TiO₂ NTAs is enhanced. The range of absorption wavelengths changes from 400 to 700 nm due to the surface plasmon response of Cu metals core and Cu₂O nanoparticles shell. The photocatalytic hydrogen production rate of Cu₂O/Cu/TiO₂ heterojunction arrays is enhanced when compared with those of Cu₂O/TiO₂ NTAs and TiO₂ NTAs under UV light. Moreover, a stable H₂ generation property was obtained under visible light (λ gt; 400 nm). The Cu metal core is believed to play a key role in the enhancement of photocatalytic properties of Cu₂O/Cu/TiO₂ nanotube heterojunction arrays.     

In situ construction of oxygen deficient MoO3-x nanosheets/porous graphitic carbon nitride for enhanced photothermal-photocatalytic hydrogen evolution

In this work, the photocatalysts containing oxygen-deficient molybdenum oxide and macroscopic three-dimensional porous graphitic carbon nitride phase composite (MoO_3-x/PCN) were prepared by in situ self-assembly method. The crystal phase and structure were characterized by XRD, XPS, FT-IR, SEM, and TEM measurements. Hydrogen production results showed that introducing of MoO_3-x resulted in a higher hydrogen production rate of MoO_3-x/PCN composite catalyst than that of PCN. Among them, the highest hydrogen production rate of 2336.15 μmol g⁻¹ h⁻¹ was achieved for MoO_3-x-10/PCN, which was 2.23 times higher than PCN (1048.00 μmol g⁻¹ h⁻¹). When the reaction system temperature was 100 °C, the photothermal hydrogen production rate of MoO_3-x-10/PCN was 8902.00 μmol g⁻¹ h⁻¹, which was 3.81 times higher than that at room temperature. PL spectra, UV–vis spectra and photoelectrochemical measurements showed that the localized surface plasmon resonance (LSPR) effect of MoO_3-x effectively enhanced the photo response range and increased the temperature of the reaction system. ESR measurements showed that he composites should follow the Z-scheme charge transfer mechanism, the electrons in the CB of MoO_3-x further migrate to the VB of PCN, which hinders the charge complexation in MoO_3-x and PCN, improving the hydrogen production activity. This study provides a new idea for constructing a plasma-based photothermal synergistic catalytic hydrogen production strategy.     

Test of conductor and semiconductor electrocatalysts in high voltage alkaline electrolyzer as production media for green hydrogen

Despite the restricted success of conductor and semiconductor electrodes in solving hydrogen production problems, they provide a promising alternative to expensive conventional electrodes in water electrolysis investigations. Titanium dioxide (TiO₂) and silver (Ag) are widely used as photocatalysts in water splitting systems for hydrogen generation. Though TiO₂ is an inactive chemical semiconductor with poor conductivity, it has not been entirely investigated as an electrocatalyst yet. Two criteria were used to achieve this target: supplying high voltage to overcome the TiO₂ large band gap and immersing it in an alkaline solution to activate its inert surface. For comparison study, Ag noble metal nanoparticles coating was employed as a competitive electrocatalyst. In this regard, the application of Ag and TiO₂ coated on Ti electrodes in a hydrogen production system operated under high voltage was reported. The nanoparticles were synthesized using cost-effective and simple methods based on UV-deposition for Ag nanoparticles and the chemical precipitation method for TiO₂ nanoparticles. Then the synthesized nanoparticles were deposited on the Ti electrodes by simple immersion. The synthesized nanoparticles and coated electrodes were tested by XRD, SEM, and EDS to study their morphology, structure, particle size, and surface composition. Based on these results, TiO₂ nano-powder and coated electrodes exhibited homogenous spheres with a mixture of rutile and anatase phases, the majority being the anatase phase. The Ag-coated Ti substrate possessed a smaller crystallite size compared to TiO₂ coated substrate. To evaluate the performance of Ag/Ti and TiO₂/Ti electrodes toward hydrogen production, H₂ flow rates were measured in a 3.6 M KOH electrolytic solution at 6 V. Hydrogen flow rates obtained for pure Ti, Ag, and TiO₂ electrodes at a steady state were 21, 35, and 37 SCCM (standard cm³/min), respectively. Also, it was found that energy consumption was reduced when the electrodes were coated with nanoparticles. Furthermore, the electrolyzer's performance was assessed by calculating the hydrogen production efficiency and the voltage efficiency. The results showed that using TiO₂ electrodes gave the best hydrogen production and voltage efficiencies of 27% and 23%, respectively. This study brings new insights about Ag and TiO₂ coated electrodes in alkaline water electrolysis at high voltage regarding nanoparticle performance, hydrogen production, system performance, and energy consumption. In addition, minimizing the fabrication and operation costs of hydrogen production is the major enabler for the broad commercialization of water electrolysis devices.     

Bandgap control of p-n heterojunction of Cu–Cu2O @ ZnO with modified reduced graphene oxide nanocomposites for photocatalytic hydrogen evolution

Here, we describe the in-situ synthesis of multicomponent ZnO-based photocatalysts for hydrogen production. We fabricated ZnO coupled with Cu–Cu₂O nanoparticles and modified reduced graphene oxide (mRGO) to ameliorate hydrogen production. The simultaneous introduction of mRGO and Cu–Cu₂O enhanced the generation rate of photocatalytic hydrogen to 3085.02 μmol g^?1 h^?1 due to significant alteration of the electronic structure. The bandgap energy of the prepared catalysts decreased from 3.2 eV for pristine ZnO to 2.64 eV for a composite containing 15% Cu–Cu₂O. The optimal designed heterostructure efficiently separates photo charge carriers and prevents charge carriers’ recombination by accelerating charge transfer with the help of mRGO and metallic Cu and as a result leading to efficient hydrogen yields.     

Investigation of plasmonic Cu with controlled diameter over TiO2 photoelectrode for solar-to-hydrogen conversion

Plasmonic metal nanoparticles (NPs) have been used to improve the solar-to-hydrogen conversion efficiency. Relative to Au and Ag, Cu is cheaper and more abundant. In the present work, Cu NPs with the controlled diameter were deposited on TiO₂ nanotube arrays (TNTAs) by using a pulse electrochemical deposition method. When the deposition was cycled 3600 times, the size of Cu NPs can be tuned to approximately 30 nm with the most uniform distribution, resulting in the remarkable characteristic peak of surface plasmon resonance and higher photocurrent density. The hydrogen production rates remained unchanged during irradiation (AM 1.5, 100 mW/cm²) of 2 h, indicating a good stability of the resultant Cu/TNTAs electrode. The photoelectrochemical performances of as-prepared Cu/TNTAs can also be comparable to those of Ag/TNTAs electrode fabricated by the same method.     

Construction of ternary Z-scheme covalent triazine framework@Au@TiO2 for enhanced visible-light-driven hydrogen evolution activity

One key challenge in photocatalytic hydrogen production is how to construct high-performance photocatalyst. Covalent triazine framework (CTF) based polymers as photocatalysts show great application potential because of their good photocatalytic activity, high chemical stability, tunable electronic and optical properties, and easy synthesis process. In this paper, we designed the ternary Z-scheme heterojunction Au@TiO₂-X%TrTh based on CTF polymer TrTh, TiO₂ and Au nanoparticle, which exhibit higher photocatalytic hydrogen production rate compared with the corresponding binary heterojunction Au@TiO₂ and TiO₂-12%TrTh. The results of photocatalytic hydrogen production show that the optimized Au@TiO₂-12%TrTh has a remarkable hydrogen production rate of 4288.54 μmol g^?1 h^?1, which is about 312.3 times of Au@TiO₂ and 9.1 times of the TiO₂-12%TrTh. The enhanced hydrogen production activity of the ternary heterojunction comes from the local surface plasmonic resonance effect of Au nanoparticle, lower recombination efficiency of photogenerated electron-holes pairs and Z-scheme electron transfer pathway of Au@TiO₂-12%TrTh. The work provides a new strategy for designing efficient and practical photocatalyst.     

Exploiting multiferroicity of TbFeO3 nanoparticles for hydrogen generation through photo/electro/photoelectro-catalytic water splitting

Hydrogen is a potential future energy source that could replace conventional fuel and provide the necessary energy. Multiferroic materials are the most likely choices for water splitting due to their ferroelectric characteristics and ability to function as magnetically recoverable catalysts. Multiferroic terbium orthoferrite nanoparticles were synthesized at low temperature by the polymeric citrate precursor route to study the photocatalytic, electrocatalytic and photoelectrochemical activity towards hydrogen production. Powder X-ray diffraction revealed successful formation of orthorhombic TbFeO₃ nanoparticles. A larger aspect ratio of 3.9 and a bandgap of 2.13 eV were seen in the elongated TbFeO₃ nanoparticles, which contributes to the photo/electro-catalytic activity. Magnetic and ferroelectric studies revealed weak ferromagnetism and ferroelectric polarization of 0.037 μC cm^?2 in TbFeO₃ nanoparticles, confirming multiferroicity. Visibly active and multiferroic TbFeO₃ nanoparticles showed notable hydrogen evolution of 1.44 mmol h^?1 g^?1. In electrocatalytic and photoelectrochemical water splitting investigations, TbFeO₃ nanoparticles demonstrated current densities of 30 and 60 mA cm^?2, respectively. EIS, TRPL, transient photocurrent and Mott-schottky measurements were used to examine charge transfer kinetics. The high H₂ evolution and good OER/HER tests were attributed to increased charger separation efficiency due to ferroelectricity induced band bending.     

Efficient photocatalytic H2 evolution over Cu and Cu3P co-modified TiO2 nanosheet

Schottky junction and p-n heterojunction are widely employed to enhance the charge transfer during the photocatalysis process. Herein, Cu and Cu₃P co-modified TiO₂ nanosheet hybrid (Cu–Cu₃P/TiO₂) was fabricated using an in situ hydrothermal method. The ternary composite achieved the superior H₂ evolution rate of 6915.7 μmol g^?1 h^?1 under simulated sunlight, which was higher than that of Cu/TiO₂ (4643.4 μmol g^?1 h^?1) and Cu₃P/TiO₂ (6315.8 μmol g^?1 h^?1) and pure TiO₂ (415.7 μmol g^?1 h^?1). The enhanced activity can be attributed to the collaboration effect of Schottky junction and p-n heterojunction among Cu/TiO₂ and Cu₃P/TiO₂, which can harvest the visible light, reduce the recombination of charge carriers and lower the overpotential of H₂ evolution, leading to a fast H₂ evolution kinetics. This work develops a feasible method for the exploration of H₂ evolution photocatalyst with outstanding charge separation properties.     

Photocatalytic hydrogen evolution and antibiotic degradation by S-scheme ZnCo2S4/TiO2

In this study, ZnCo₂S₄ (ZCS) nanoparticles were coupled on the surface of TiO₂ by simple solvothermal method to form S-scheme heterojunction. Compared with ZCS and TiO₂, the photocatalytic performance of ZCS/TiO₂ under simulated sunlight is significantly improved, and its hydrogen evolution efficiency reaches 5580 μmol·g^?1·h^?1 with the apparent quantum efficiency (AQY) up to 11.5% at 420 nm, which is 88.3 times and 54.3 times that of TiO₂ and ZCS, respectively. Moreover, ZCS/TiO₂ also has excellent performance in the photocatalytic degradation of tetracycline (TC). The enhancement of photocatalytic performance of ZCS/TiO₂ is mainly due to S-scheme heterojunction. On the one hand, the S-scheme electron transfer path not only improves the electron-hole separation efficiency, but also improves the charge transfer efficiency. On the other hand, ZCS significantly enhances the visible light absorption of ZCS/TiO₂. The photocatalytic mechanism and S-scheme heterojunction structure is confirmed by XPS, EPR, ultraviolet photoelectron spectroscopy (UPS) and energy band structure. This work provides a new idea for designing and constructing S-scheme heterojunction to improve the performance of photocatalytic hydrogen evolution and TC degradation.     

Photoelectrochemical hydrogen production from water/methanol decomposition using Ag/TiO2 nanocomposite thin films

Though less frequently studied for solar-hydrogen production, films are more convenient to use than powders and can be easily recycled. Anatase TiO₂ films decorated with Ag nanoparticles are synthesized by a rapid, simple, and inexpensive method. They are used to cleave water to produce H₂ under UV light in the presence of methanol as a hole scavenger. A simple and sensitive method is established here to monitor the time course of hydrogen production for ultralow amounts of TiO₂. The average hydrogen production rate of Ag/TiO₂ anatase films is 147.9 ± 35.5 μmol/h/g. Without silver, it decreases dramatically to 4.65 ± 0.39 μmol/h/g for anatase TiO₂ films and to 0.46 ± 0.66 μmol/h/g for amorphous TiO₂ films fabricated at room temperature. Our method can be used as a high through-put screening process in search of high efficiency heterogeneous photocatalysts for solar-hydrogen production from water-splitting.     

One-pot synthesis of Cu–TiO2/CuO nanocomposite: Application to photocatalysis for enhanced H2 production,dye degradation & detoxification of Cr (VI)

Photocatalytic hydrogen production under the visible spectrum of solar light is an important topic of research. To achieve the targeted visible light hydrogen production and improve the charge carrier utilization, bandgap engineering and surface modification of the photocatalyst plays a vital role. Present work reports the one-pot synthesis of Cu–TiO₂/CuO nanocomposite photocatalyst using green surfactant -aided -ultrasonication method. The materials characterization data reveals the TiO₂ particle size of 20–25 nm and the existence of copper in the lattice as well as in the surface of anatase TiO₂. This is expected to facilitate better optical and surface properties. The optimized photocatalyst shows enhanced H₂ production rate of 10,453 μmol h⁻¹ g⁻¹ of the catalyst which is 21 fold higher than pure TiO₂ nanoparticles. The photocatalyst was tested for degradation of methylene blue dye (90% in 4 h) in aqueous solution and photocatalytic reduction of toxic Cr⁶⁺ ions (55% in 4 h) in aqueous solution. A plausible mechanistic pathway is also proposed.     

Enhanced photocatalytic hydrogen evolution from reduced graphene oxide-defect rich TiO2-x nanocomposites

Solar-driven photocatalytic hydrogen generation by splitting water molecules requires an efficient visible light active photocatalyst. This work reports an improved hydrogen evolution activity of visible light active TiO_2-x photocatalyst by introducing reduced graphene oxide via an eco-friendly and cost-effective hydrothermal method. This process facilitates graphene oxide reduction and incorporates intrinsic defects in TiO₂ lattice at a one-pot reaction process. The characteristic studies reveal that RGO/TiO_2-x nanocomposites were sufficiently durable and efficient for photocatalytic hydrogen generation under the visible light spectrum. The altered band gap of TiO_2-x rationally promotes the visible light absorption, and the RGO sheets present in the composites suppresses the electron-hole recombination, which accelerates the charge transfer. Hence, the noble metal-free RGO/TiO_2-x photocatalyst exhibited hydrogen production with a rate of 13.6 mmol h^?1g^?1_cat. under solar illumination. The appreciable photocatalytic hydrogen generation activity of 947.2 μmol h^?1g^?1_cat with 117 μAcm^?2 photocurrent density was observed under visible light (>450 nm).