Calcination Treatment Research Articles

TiO2 Hollow Nanofiber/Polyaniline Nanocomposites for Ammonia Detection at Room Temperature

AbstractAmmonia (NH3) detection has gained considerable attention in agricultural and environmental monitoring, chemical and pharmaceutical processing, and disease diagnosis, which requires the development of sensors with high sensitivity. Herein, we propose a novel gas sensor based on nanocomposites of TiO2 hollow nanofibers and polyaniline (PANI) for the sensitive detection of ammonia at room temperature. TiO2 nanostructures in anatase phase were prepared by the combination of coaxial electrospinning and calcination treatment. The resulting material was mixed with PANI and deposited onto gold interdigitated electrodes (IDEs). The hybrid platforms exhibited superior sensing performance compared to the platform based on their individual phases, which is ascribed to a synergistic effect from p‐n heterojunction formation. Specifically, the platforms based on TiO2/PANI nanocomposite showed a fast response towards NH3 (e. g., 55 s at 10 ppm) at room temperature (25 °C). Additionally, the platform demonstrated the ability to detect NH3 at low concentrations (10–30 ppm) and a detection mechanism was proposed to explain the results. Overall, these results show the promise of electrospun TiO2 hollow nanofibers/PANI composites for the development of high‐performance room temperature ammonia sensors.

Oxygen vacancies Nb2O5-x: Ultrastable lithium storage anode materials for advanced rechargeable batteries

Optimizing the charge and ion transport of Nb2O5 composite is great significance for developing high-performance fast charge lithium-ion batteries. We designed Nb2O5 with oxygen vacancies through a simple and cost-effective hydrothermal and high-temperature calcination treatments. Oxygen vacancies can not only improve the electronic conductivity of the composite, but also effectively provide more active sites and reduce the ion transport barrier, which improved electrochemical reaction kinetics of the Nb2O5 composite. Consequently, the synthesized Nb2O5-x microflowers delivered a specific capacity of 191.2 mA h g−1 at 1C (a retention of 94% over 200 cycles) and outstanding rate capability (103.3 mA h g−1 at 50C) for lithium storage. Significantly, this work may also broaden the pathways for designing other electrode materials with oxygen vacancies for battery systems.

Growth of uniform CuCo2O4 porous nanosheets and nanowires for high-performance hybrid supercapacitors

In this work, uniform CuCo2O4 nanowires (CCO-NWs) and nanosheets (CCO-NSs) were directly grown on the stainless-steel foil via a hydrothermal process with a post calcination treatment in air, and powdered CuCo2O4 materials were obtained once they were peeled off from the stainless-steel substrate. These NWs- and NSs-based powders possessed a huge specific surface area and mesoporous feature. After electrochemical tests, it was found that the CCO-NWs delivered a capacity of 299.12 C g−1 and CCO-NSs could exhibit a capacity of up to 332.18 C g−1. A hybrid supercapacitor (HSC) was assembled with activated carbon (AC) as anode to evaluate the practical applications of CuCo2O4 in energy storage. The CCO-NWs//AC HSC exhibited an energy density of 36.16 W h kg−1 at 1.01 kW kg−1, and as for the CCO-NSs//AC HSC, it delivered 38.46 W h kg−1 at the power density of 1.03 kW kg−1. Both HSCs showed excellent cycling performance over 5000 cycles at 6 A g−1. The superior electrochemical performance of CuCo2O4 NWs and NSs indicates that the battery-type CuCo2O4 electrode materials can serve as advanced cathode for high-performance supercapacitors, and the simple synthetic method can be extended to the preparation of other transition metal oxides (TMOs)-based electrode materials with uniform structure and impressive electrochemical properties.

Synergistic effect of nanosheet structure and carbon coating engineering to enhance lithium storage performance of molybdenum niobium oxides

Improving the conductivity of electrode materials and the migration rate of lithium-ions in the working process, and keeping the structure of the battery stable in the charging and discharging process are the key to preparing higher capacity and safer lithium-ion batteries. In this work, a novel morphology of carbon-coated MoNb12O33 (MNO) nanosheet was successfully synthesized by precisely regulating the concentration, and combining the solvothermal method and the high temperature calcination treatment. The unique porous nanosheet structure is more favorable for shortening the ion transport distance between electrode and electrolyte than MNO with other morphological structures due to its larger contact area. In addition, the carbon shell can interconnect MNO particles into a conductive network that improves the conductivity of composites as well as serve as an armor that maintains the structure stable during the electrochemical behavior. Consequently, the initial coulombic efficiency of the flaky MNO coated with carbon (F-MNO@C) is 96.29%, and the specific capacity can be maintained at 144.23 mA h/g after 1000 cycles test at 10 C, which is still higher than 88.75 mA h/g of the pristine MNO (F-MNO).

One-Pot Synthesis of Hexamethylenetetramine Coupled with H2 Evolution from Methanol and Ammonia by a Pt/TiO2 Nanophotocatalyst.

Utilization of solar energy for photocatalytic H2 evolution coupled with value-added chemical synthesis is a promising avenue to address energy and environmental crises. Here, we report the hexamethylenetetramine (HMT) synthesis and H2 evolution from methanol and ammonia in one pot using a nanophotocatalyst of the conventional semiconductor TiO2 (P25) loaded with Pt (Pt/P25). The addition of ammonia inhibits byproduct ethylene glycol formation, promotes H2 evolution, and obtains HMT with high selectivity (>99.0%). The Pt valence state is regulated by calcination and reduction treatment, indicating that Pt/P25 is a stable catalyst for the photocatalytic synthesis of HMT from methanol and ammonia. The optimized formation rates of H2 and HMT are 71.53 and 11.39 mmol gcat–1 h–1, respectively. This work provides a green and sustainable pathway for the photocatalytic HMT synthesis coupled with H2 evolution under mild conditions.

A bimetallic (Co/Fe) modified nickel foam (NF) anode as the peroxymonosulfate (PMS) activator: Characteristics and mechanism

A bimetallic (Co/Fe) modified nickel foam (NF) anode was fabricated as an effectively electrochemical peroxymonosulfate (PMS) activator for the removal of tetracycline (TC). The results showed that the bimetallic modification through solvothermal treatment could result in a significant increase of electrochemical properties, which were further enhanced by the subsequent calcination treatment at 400 ℃. The fabricated c-CoFe-NF anode showed high catalytic performance as the PMS activator and the TC removal efficiency could reach 93.05 % within 1 h. The activation energy (21.23 kJ/mol) during PMS activation by c-CoFe-NF anode was about 2.58 times lower than that of bare NF anode (54.79 kJ/mol), and the corresponding reaction rate was enhanced by 2.68 times. The quenching experiments and the electron paramagnetic resonance (EPR) tests showed that the generated reactive oxygen species (including O2- and 1O2) and SO4- played important roles in TC removal. 1O2 was mainly originated from the dismutation of O2-, while the O2- was generated via hydrolysis of SO4- and the electrochemical oxygen reduction reaction (ORR). Furthermore, EPR investigation results also demonstrated that the SO4- formed during the anodic PMS activation became the main contributor for the generation of the reactive oxygen species. The current investigation gave a comprehensive and new insight into the roles and characteristics of the transformation among different reactive radicals generated during the anodic PMS activation process. Furthermore, the fabricated c-CoFe-NF anode provided an alternative for the degradation of pollutants applied in wastewater treatment based on the electrochemical advanced oxidation process (EAOP)

Oxygen uncoupling behaviour for ilmenite ore oxygen carrier generated from a calcination treatment mixed with natural manganese ore

AbstractChemical looping with O2 uncoupling aims at using an oxygen carrier (OC) with O2 uncoupling behaviour to promote fuel conversion. Natural ilmenite ores have been considered highly promising OCs for chemical looping technology; however, they do not possess any O2 uncoupling behaviour. Mn‐modified ilmenite ores as OCs are capable of O2 uncoupling, while most of them are synthesized via complicated procedures by using costly chemicals. In this study, a strategy of calcination treatment on ilmenite ores mixed with manganese ores has been established to introduce Mn into the ilmenite OCs, endowing them with O2 uncoupling behaviour in a simple and low‐cost manner. The O2 uncoupling behaviour from Mn‐modified ilmenite ores is mainly due to the newly formed (Fe1−xMnx)2O3/(Fe1−xMnx)3O4 crystal phases generated during the calcination treatment, which also alleviate the thermodynamic limit of the Mn2O3‐Mn3O4 redox pair. As a result, the Mn‐modified ilmenite ore OCs can release O2 at high temperatures when decreasing the oxygen partial pressure. But more importantly, the reduced OCs can be restored in the air isothermally. This established simple calcination treatment method can be used as a low‐cost strategy for producing ilmenite‐based OCs with O2 uncoupling behaviour. The O2 uncoupling behaviour is expected to be beneficial to chemical looping combustion of fuels, promote fuel conversion, minimize OC loading, and reduce energy consumption.

Preparation of TiO2-nanotube-based photocatalysts and degradation kinetics of patulin in simulated juice

Patulin (PAT) is a heat-stable mycotoxin produced by several fungal species belonging to the genera Penicillium and Aspergillus, in damaged or moldy fruits. In this work, TiO2 nanotubes (TNTs) were prepared as photocatalysts for the degradation of PAT in simulated juice, by a hydrothermal method coupled with calcination treatment. Their physical, chemical, optical, and adsorption properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), photoluminescence (PL), and N2 adsorption–desorption isotherms, to optimize the preparation conditions. The photocatalytic activities of the TNTs were evaluated by the degradation of PAT in a simulated juice, under ultraviolet (UV) irradiation. The results showed that TNTs-450 calcinated at 450 °C for 2 h had high adsorption performance and photocatalytic activity in the amorphous state, and 1000 mg/L of TNTs-450 can completely degrade 1000 μg/L PAT in the simulated juice within 25 min. The kinetics of the photocatalytic degradation of PAT were then studied under various reaction conditions, showing that the photocatalytic degradation of PAT by TNTs-450 in the simulated juice followed first-order kinetics (R2 ≥ 0.97). However, the UV light intensity and the pH of the reaction system are the main factors affecting the rate of PAT degradation. In addition, the Langmuir–Hinshelwood model can explain the photocatalytic degradation of PAT by TNTs-450 well, following the adsorption-surface reaction-desorption step.

Recycling phosphogypsum in subbase of pavement: Treatment, testing, and application

This study aims to recycle the phosphogypsum (PG) as pavement subbase material. First, the physical and chemical properties of the PG before and after calcination treatment were characterized. Then the mix design, as well as the performance evaluation of the PG mixture, were detailed. Finally, the engineering application and economic analysis of the PG mixture for paving subbase pavement were presented. It is found that incorporation of the calcined PG (CPG) can help form gel structure to stabilize the PG. Meanwhile, addition of lime can neutralize the water-soluble phosphorus contained in the PG to improve the early strength of the CPG-stabilized PG. The optimal mix proportion of the CPG-lime stabilized PG by mass is determined as PG: CPG: lime = 89: 9: 2. In addition, as compared to the PG stabilized with the traditional inorganic binder materials, the CPG-lime stabilized PG has higher unconfined compressive strength (UCS) and better resistance to the water damage and fatigue damage caused by the water content variation. The field cores extracted from the paved CPG-lime stabilized PG subbase were experimentally observed to have a 7 d UCS as high as 3.69 MPa. Moreover, reuse of the CPG-lime stabilized PG is proven to be a highly economic and environment-friendly pathway for subbase paving, of which total cost per unit cube meter is 504.5 % lower than that of the commonly-used lime-fly ash stabilized soil. These findings identify the feasibility of utilizing the PG for pavement subbase construction.

Mesoporous peroxidase nanozyme for synergistic chemodynamic therapy and chemotherapy

Peroxidase nanozyme, enabling decomposition of hydrogen peroxide (H2O2) into highly toxic hydroxyl radical (•OH), is an emerging technology for tumor treatment. However, limited by the low H2O2 level in the tumor microenvironment, the standalone peroxidase nanozyme-mediated therapy usually fails to achieve desirable therapeutic outcomes. Herein, we presented a mesoporous nanozyme that not only had peroxidase-like activity but also could deliver anticancer drug for synergistic tumor therapy. The nanozyme, that was, iron-doped mesoporous silica nanoparticle (FeMSN), was prepared by a sol-gel method and then a calcination treatment. The introduction of iron endowed FeMSN with peroxidase-like activity that could decompose H2O2 into •OH under acidic condition for chemodynamic therapy of tumors. Meanwhile, the mesoporous structure enabled FeMSN to deliver anticancer drug doxorubicin (DOX) for chemotherapy and enhanced chemodynamic therapy through H2O2 production, ultimately achieving synergistic effect to improve the efficacy of tumor treatment. The in-vitro and in-vivo results demonstrated that DOX-loaded FeMSN exhibited significant cancer cell-killing effect and potently inhibited tumor growth. Collectively, this study represented a paradigm for achieving efficient tumor therapy through design of peroxidase-like nanozyme with drug delivery capability, which might advance the development of nanozyme in tumor chemodynamic therapy.

Circular conversion of waste rectorite@dye to efficient and pH-resistant heterogeneous silicate adsorbents for cyclic and complete dye removal

A series of new heterogeneous silicate adsorbents were synthesized from waste dye-adsorbed rectorite (named as rectorite@dye) through conventional calcination, hydrothermal treatment and an upgraded oxidation-promoted conversion process. Compared with conventional calcination and direct hydrothermal treatment processes, the positive effect of oxidants such as hydrogen peroxide and calcium peroxide on improving the conversion efficiency of rectorite@dye waste and adsorption properties was studied. It was revealed that hydrogen peroxide promoted the conversion of waste rectorite@dye into a heterogeneous rectorite@carbon composite with a carbon content of 1.38% and nitrogen content of 0.44%. The optimal rectorite@carbon adsorbent can efficiently adsorb Methylene blue at 176.77 mg/g and Basic red 14 at 305.87 mg/g, which shows superior performance than rectorite@dye (44.26 mg/g for Methylene blue; and 25.26 mg/g for Basic red 14) and composite adsorbents prepared by conventional calcination (141.52 mg/g for Methylene blue; 213.03 mg/g for Basic red 14) or direct hydrothermal treatment (74.47 mg/g for Methylene blue and 88.34 mg/g for Basic red 14). The adsorption capacity of the adsorbent is pH-independent, and it can be used over a wide pH range. Moreover, the composite adsorbents can remove 99.99% of Methylene blue and 99.90% of Basic red 14 from an initial 100 mg/L dye solution, and thus clean water was obtained after treating dye-polluted water with the rectorite@carbon adsorbents. After each adsorption cycle, the waste adsorbent can be regenerated by a one-step calcination or hydrothermal process and reused, and the adsorption capacity of the regenerated adsorbent can still reach 198.43 mg/g (for calcination regeneration) and 268.35 mg/g (for hydrothermal regeneration) after 6 regenerations.

Effects of calcination parameters on the purity, morphology, and electrochemical properties of the synthesized TiNb2O7 by the solvothermal method as anode materials for Li-ion batteries

This study aims to investigate the effects of calcination parameters including temperature (700, 800, and 900 °C) and holding time (5 and 10 h) on the purity, morphology, and Li-ion storage performance of the TiNb2O7 synthesized by the solvothermal method. The X-ray diffraction (XRD) results showed that the application of calcination treatment at 700 and 800 °C for 5 h in the air atmosphere resulted in the formation of the dual-phase product of TiNb2O7-Nb2O5 while the pure TiNb2O7 was obtained only by increasing the calcination temperature to 900 °C. The morphological analyses showed the formation of the TiNb2O7 porous microspheres with a diameter of 500 nm constructed by nanoparticles. On the other hand, results indicated that increasing the holding time from 5 to 10 h at a constant calcination temperature of 900 °C resulted in the occurrence of morphological evolution from porous microspheres to faceted irregular particles and particle growth. The electrochemical characterization of the pure samples showed that the TiNb2O7 porous microsphere had a very better electrochemical performance over the faceted sample in the cases of Li-ion storage capability, and rate capability while its cyclic stability was lower than faceted TiNb2O7.

Novel green route synthesis of CdO nanostructures by using CdCO3 obtained by MICP and its application in photodegradation of methylene blue and Congo red

This research developed a new green route synthesis of cadmium oxide (CdO) nanostructures. First, the microbially induced carbonate precipitation was employed as a bioremediation strategy of Cd+2 in wastewater using granular sludge to precipitate it as cadmium carbonate (CdCO3) crystals. Then, the CdCO3 powder was subjected to calcination treatment at 450°C for 10, 20, 30, and 60 min to convert it to CdO and remove organic compounds. The characterization results showed that CdCO3 was converted entirely to CdO at 60 min of the thermal annealing at 450°C. CdO exhibited a simple cubic structure with an average crystallite size of 28 nm. Scanning electron microscopy images showed agglomerations composed of CdO tube-like nanostructures with an average of 60 nm in diameter. The optical energy band-gaps of the CdO nanostructures were 2.15 eV and 2.0 eV for direct and indirect transitions, respectively.Finally, the CdO nanostructures exhibited excellent removal efficiencies for Methylene blue and Congo red photodegradation at 120 min with apparent rate constants of 0.013 and 0.009 min−1, respectively.

Sewage sludge thermochemical treatment with MgCl2: Preparation conditions impact on trace metal elements vaporization and phosphorus recovery

Phosphorus (P) plays an essential role in crops growth. Due to the overexploitation of non-renewable phosphate rock deposits and their uneven distribution worldwide, P has turned into a strategic resource for the modern agricultural system. Finding sustainable ways to secure P for fertilizer applications has become critical. Sewage sludge (SS) is a waste material containing P in high amounts. Among several options, SS thermochemical treatment with Cl-donors addition such as MgCl2, CaCl2 or NaCl allows to separate P from inorganics pollutants such as trace metal elements (TME). The additives goal is to help fix and form bioavailable P species in solid residues while promoting TME vaporization through the gas phase via chlorination mechanisms. This paper studies the impact of MgCl2 addition on TME vaporization and P speciation during SS direct calcination treatment at 1000 °C for 4 h. Four different preparation methods for the “SS + MgCl2” mixtures were compared, with a variation of either the SS (raw or crushed) or the MgCl2 form (powder or solution). The samples were characterized by ED-XRF, FTIR, XRD, TGA/DSC and the P speciation was obtained thanks to Williams-Saunders method. The use of 0.06 g MgCl2/g SS as a Cl-donor divides the TME contents in the solid residues by a factor of more than 10 for Zn and Pb, about 2 for As and Ni but less than 1.25 for Cu. Concerning P, Ca associated P species (mostly Mg3Ca3(PO4)4) are formed with MgCl2 addition. The results showed that the impact of different preparation methods on the obtained solid residues characteristics is limited.

Green synthesis with Aloe Vera of MgAl2O4 substituted by Mn and without calcination treatment

Magnesium aluminates (MgAl2O4) with Mn substituting sites A and B were synthesized by the microwave-assisted combustion method applying high power (900 W) using Aloe Vera as a green chelating agent. The study evaluated the effect of the presence of Aloe Vera and the subsequent heat treatment on the structural characteristics of spinel powders by X-ray diffraction (XRD). The effect of heat treatment was evaluated in two ways: with and without calcination. The results showed that the substitutes occurred forming the following phases: Mg0.21Mn2.36Al0.43O4, Mg0.13Mn2.63Al0.25O4, Mg0.31Mn2.06Al0.63O4 substituting site A; and MgMn1.88Al0.13O4 and MgMn1.75Al0.25O4 substituting site B. The presence of Mn and Aloe Vera ions affected the spinel crystal structure. The crystallinity degree is less intense when the magnesium aluminate was substituted by the Mn ion due to the amount of deformations in the crystal system induced by the substituent ion. However, the calcination of the powders increased the crystallinity degree in all scenarios. Furthermore, the substitution caused alteration in the lattice parameters due to the difference between the ionic radius of the substituent and the Mg2+ or Al3+ ion evidenced in the positions of 2θ. The spinel cubic phase was found in most materials, although the tetrahedral phase was observed in some Mn-substituted structures. The crystallite sizes of the powders were influenced by the presence of phytochemicals present in Aloe Vera. A decrease in crystallite size was observed when the materials were calcined as a result of the gasification of biomolecules from the plant extract. However, these biomolecules help in dissociating precursors, albeit slowly, which prevented crystallite growth. The use of Aloe Vera as a chelating agent proved to be efficient in the synthesis of magnesium aluminate spinels, pointing out the synthesized material as a promising route for the green synthesis field.

Reducing Valence States of Co Active Sites in a Single‐Atom Nanozyme for Boosted Tumor Therapy

AbstractThe construction of biocompatible and trackable‐imaging single‐atom nanozymes (SAzymes) with efficient catalytic activities is particularly desirable. Here, cobalt/titanium oxide (Co/TiO2) SAzymes are presented with cobalt atomically dispersed on nanoporous hollow TiO2 using a cation‐exchange strategy. Significantly, by varying the calcination conditions, the enzyme‐like activity can be enhanced tenfold. It is determined that different calcination treatments result in valence state shifts of the Co active site due to changes in the amounts of defects, which affects the catalytic kinetics. Moreover, Co/TiO2 SAzymes exhibit good intrinsic biocompatibility and excellent tolerance toward the biological medium, while the hollow structure facilitates the loading of drugs and imaging agents for image‐guided chemo‐chemodynamic therapy via intravenous injection. This study not only provides a paradigm shift for the preparation of biocompatible SAzymes but also presents new insights for modulating the catalytic activity of SAzymes.

Effect of flue gas impurities in carbon dioxide from power plants in the synthesis of isopropyl N-phenylcarbamate from CO2, aniline, and 2-propanol using CeO2 and 2-cyanopyridine

Current CO2 utilization technologies generally start with purification of CO2, which requires considerable energy input. Using CO2-containing flue gases as a feedstock in chemical conversions of CO2 can help simplify pre-treatment of CO2 and reduce the carbon footprint of the process, however, study of the effects of other components in the flue gases in chemical reactions using CO2 is limited. Our previous study demonstrated that the combination catalyst system of CeO2 and 2-cyanopyridine was effective for the reaction of pure CO2, aniline, and 2-propanol to afford isopropyl N-phenylcarbamate, which is a promising precursor for polyurethane, in over 90% yield. In this study, the addition effect of other components in CO2-containing flue gases namely N2, O2, SO2 (ppm-order) and NO2 (ppm-order) on the reaction was investigated. The addition of N2 and NO2 had almost no influence on the catalytic performance, however, that of O2 and SO2 had some negative effects. The addition of O2 decreased the selectivity and yield to the target carbamate due to the formation of aniline-derived byproducts such as aniline-coupling products and aniline-oligomers. The increase of the amount of 2-cyanopyridine and 2-propanol was effective for the suppression of the aniline-derived byproducts, providing a similar yield of the isopropyl N-phenylcarbamate to the case without any additives. The catalyst system was strongly poisoned by addition of SO2, and the activity of CeO2 was not recovered even by calcination treatment.

Designing highly sensitive formaldehyde sensors via A-site cation deficiency in LaFeO3 hollow nanofibers

In this work, a facile strategy to improve the formaldehyde (HCHO) sensing performance via introducing A-site cation deficiency of LaFeO3 hollow oxides is reported. One-dimensional LaxFeO3 hollow nanofibers (LxFO HNFs, x = 1.0, 0.9, 0.8, 0.7, and 0.6) were prepared through electrospinning technique and subsequent calcination treatment. Benefiting from the hollow nanostructures and the existed A-site cation deficiency in LxFO HNFs, all the rapid charge transfer, abundant oxygen vacancies, and chemisorbed active sites could be achieved. Among all these LxFO HNFs sensors, the non-stoichiometric L0.7FO HNFs sensor delivered a high response value of 20.4 towards 100 ppm HCHO at 180 °C, which is over 3-fold higher than that of stoichiometric L1.0FO HNFs (6.3). Moreover, L0.7FO HNFs sensor has virtues of rapid response/recovery speed (23 /13 s), high selectivity, and good long-term stability toward HCHO. The smart HCHO detection device assembled with the L0.7FO HNFs gas sensor also enabled real-time and visible HCHO monitoring, highlighting its great potential application in the smart detection of hazardous gases.

Enhanced photoproduction of hydrogen on Pd/TiO2 prepared by mechanochemistry

Supported metal clusters are considered as promising cocatalysts in heterogeneous photocatalysis due to their singular geometric structures and unique reactivity. Nevertheless, to explore efficient synthetic routes that result in stable supported clusters with tailored active sites is an urgent yet challenging task. Here, a photocatalyst with highly dispersed Pd clusters onto TiO2 is synthesized through only one-step ball milling procedure. The obtained Pd clusters form a particular metal-support interface, which has the ability to rearrange the small clusters evolving into Pd nanoparticles during the photocatalytic H2 production process, and maintain a stable photocatalytic performance up to 100 h of continuous operation. Moreover, the unique interaction between Pd clusters and titania support was only observed in the ball-milled sample, and it disappeared after a calcination treatment. The mechanochemical strategy paves the way to stabilize supported metal clusters onto semiconductors without any organic compounds involved.

Built-in electron transport channels and interfacial ions doping in BiVO4 modified with isolated Ni atoms anchored on carbon hollow matrix for boosting charge separation and transport efficiency

Here, a novel heterostructure with ions doped interfaces and electrons transport channels is firstly fabricated through a simple solid solution drying and calcination method, in which Ni atoms anchored on N-doped graphitic carbon hollow matrix was thoroughly covered by Mo, W co-doped BVO films (Mo, W: BVO/Ni@NGC). With the solidification of Mo, W: BVO during the calcination treatment, the carbon hollow matrix undergoes a crystal transformation from amorphous to graphitized, which should be beneficial for the electrons transport. The photocurrent density of Mo, W: BVO/Ni@NGC reaches 4.95 mA/cm2 at 1.23 V vs RHE in the absence of hole scavengers and oxidation co-catalysts. Experimental results demonstrated that Ni and NC contribute greatly to charge transport efficiency (ηtra) but have little influence on the charge separation efficiency (ηsep). The density functional theory (DFT) calculations have been performed to explore the origin of enhanced ηsep. Theoretical results demonstrated that interfacial Ni ions doping will result in a built-in electric field, which plays a major role in the improving of ηsep. Thus, the probable charge transfer mechanism of Mo, W: BVO/Ni@NGC is proposed, which should be valuable for the design of efficient photocatalysts.