1,720,997 research outputs found
Investigating the influential effect of etchant time in constructing 2D/2D HCN/MXene heterojunction with controlled growth of TiO2 NPs for stimulating photocatalytic H2 production
No full textWell-designed, two-dimensional hierarchical g-C3N4 (2D HCN) nanosheets anchored over two-dimensional exfoliated titanium carbide (2D TiC) multilayers embedded with in situ grown TiO2 were fabricated for stimulating H2 production under visible light. The Ti3C2 efficiency was directly influenced by varying the etching time ranging from 24 to 96 h. Using optimized 2D TiC multilayers embedded with TiO2 (anatase) with etchant time 48 h, the highest H2 yield of 182.5 µmol g-1 h-1 was attained, an obviously higher production rate than using etchant times of 24, 72, and 96 h, due to improved charge carrier separation efficiency through heterojunction formation. Hierarchical g-C3N4 exhibited 1.26 times more H2 yield than using bulk g-C3N4 due to efficient migration and transportation of charge carrier. The H2 production rate of the optimized 10TiC-48/HCN 2D/2D heterojunction reached 310 µmol g-1 h-1 which is ~1.93, 2.33, and 2.95 times higher than it was produced over TiC-48, HCN, and CN, respectively. This proficient hydrogen production was due to faster transfer of electrons from HCN to TiC-MXene due to higher conductivity and formation of heterojunction between HCN and TiO2 with their synergistic effects. The continuous production of H2 with recyclability evidenced 2D/2D heterojunction advantages and provides new insight on the role of the hierarchical MXene composite and, thus, would be beneficial for solar energy applications
Construction of a stable two-dimensional MAX supported protonated graphitic carbon nitride (pg-c3n4)/ti3alc2/tio2 z-scheme multiheterojunction system for efficient photocatalytic co2 reduction through dry reforming of methanol
No full textIn situ construction of two-dimensional (2D)/2D pg-C3N4/Ti3AlC2 MAX heterojunction was achieved using a protonated assisted sonication approach, while TiO2 nanoparticles were embedded over the layered heterostructure using a sol–gel method. This multiheterojunction system exhibits proficient charge transfer and superior activity toward photocatalytic reduction of CO2 through dry reforming of methanol (DRM). Using pg-C3N4/Ti3AlC2/TiO2 composite, H2 and CO production rates at 91.9 and 4.97 mmol (g of cat.)−1 h–1 were achieved, which are 18- and 6-fold higher than using pristine pg-C3N4, respectively. The enhancement in photocatalytic activity is mainly attributed to intimate interfacial contact due to the formation of a multiheterojunction for better light absorption, boosted electron separation, and stronger photoreductive potential. More importantly, CO2 reduction with H2O produces CO-rich syngas; however, the methanol/water mixture promoted hydrogen-rich syngas production. Higher quantum yield and prolonged stability are further achieved over the composite catalyst, attributed to the exfoliated 2D Ti3AlC2 MAX structure with strong metal/support interaction. This work demonstrates DRM as a potential approach to get hydrogen-rich syngas and provides a new pathway for the construction of highly stable 2D MAX based structured composite for water splitting and CO2 reforming applications
Binary Ni2P/Ti3C2 multilayer cocatalyst anchored TiO2 nanocomposite with etchant/oxidation grown TiO2 NPs for enhancing photocatalytic H2 production
No full textTernary nickel phosphide (Ni2P) and titanium carbide (Ti2C2) MXene supported titanium dioxide nanoparticles (TiO2 NPs) to construct a Ni2P/TiO2 NPs/Ti3C2 MXene hybrid composite for stimulating photocatalytic hydrogen production has been investigated. The performance comparison of two-dimensional (2D) Ti3C2 MXene multilayers with in situ grown TiO2 NPs synthesized through etching and atmospheric calcination methods was conducted and promising separation of charge carriers was observed. TiO2 NPs embedded over 2D Ti3C2, synthesized through both methods, were found to have promise in promoting photoactivity, whereas 2.89 times more H2 yield was attained with TiO2 NPs embedded through the oxidation (ox) approach. Using the Ni2P/TiO2/Ti3C2-ox heterostructure, a rate of 9425 ppm g-1 h-1 of H2 was reached, 2.77, 4.81, and 8.28 times more than those using Ni2P/TiO2, TiO2/Ti3C2 and TiO2 samples, respectively. This obviously augmented H2 production rate can be ascribed to a binary cocatalyst with efficient charge carrier separation, higher light absorption, and more attachment of water molecules. Among different alcohols, glycerol was a promising reagent to yield more hydrogen in addition to having higher photostability in consecutive cycles. This study provides a new approach to construct a ternary nanocomposite with proficient charge carrier separation and would be beneficial for other energy applications
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Tri-metallic Ni–Co modified reducible TiO2 nanocomposite for boosting H2 production through steam reforming of phenol
No full textWell-designed Co3O4 nanocubes (NCs) dispersed NiO/TiO2 to construct tri-metallic reducible NiO/TiO2/Co3O4 NCs structured catalyst for steam-reforming of phenol (SRP) with enhanced hydrogen production has been investigated. The controlled morphology with good dispersion was obtained, enabling efficient SRP toward selective H2 production. Using 10% NiO- 5% Co3O4 NCs/TiO2 composite, H2 yield of 69.91% and phenol conversion of 78.4% was achieved, significantly higher than using NiO/TiO2 and TiO2 samples. The cubical structured Co3O4 dispersed NiO/TiO2 composite showed significantly improved H2 yield and phenol conversion due to strong metal-support interaction with reducible support for providing more active sites. The H2 production was further increased by increasing reaction temperature, phenol concentration, feed flow rate and catalysts loading, however, they have adverse effect on the selectivity due to more CO formation. The composite catalyst possesses excellent activity and stability due to strong tri-metallic interaction and exceptional electronic interfaces. The spent catalyst analysis confirms the formation of graphene and carbon nanotubes over the reducible support. This study reveals that Co3O4 NCs are able to increase NiO/TiO2 activity for H2 production by inhibiting carbon monoxide formation and would be beneficial in other reforming applications
Current trends in strategies to improve photocatalytic performance of perovskites materials for solar to hydrogen production
No full textPhotocatalytic hydrogen production via water splitting is one of the favorable technologies for the solar energy conversion to renewable and sustainable energy; however, semiconductor materials under consideration have lower efficiency, selectivity and stability. Recently, perovskites are most demanding semiconductor photocatalysts belonging to very important family of materials and exhibit exceptional visible light response towards photocatalytic application. This review highlights recent developments in perovskite materials and their modification approaches for improved photocatalytic H2 production. Primarily, the classification of perovskites based on structural developments; in particular, thermodynamics engineering to minimize energy barriers are discussed. Different approaches for fabrication of perovskite materials by metal and non-metal doping, while focusing on mechanism of Schottky barrier and Surface Plasmon phenomenon to improve photocatalytic efficiency are explored. This review also presents band engineering approaches in perovskites such as site substitution, solid-solution formation and nitrification of perovskites to maximize H2 evolution. Elaboration of layered perovskite and improvement in their efficiency by various fabrication techniques including Z-scheme formation and composite of perovskite with TiO2 and carbon-based composites including g-C3N4 and rGO in terms of multi-component heterojunction based on transfer of electron-hole pairs are critically deliberated. Finally, future perspectives of perovskite materials and their efficiency enhancement approaches for sustainable solar to hydrogen production has been suggested
Steam reforming of phenol toward cleaner hydrogen production over bimetallic Ni/Ti modified zinc titanate perovskite in tandem with a kinetic model development
No full textHydrogen as a clean energy carrier with high heat combustion and zero environmental impacts is an attractive alternative to fossil fuels. In this study, NiO/TiO2 modified ZnTiO3 perovskite (NTZ) with high reducibility catalyst was designated by co-precipitation method and examined in the reaction of steam reforming of phenol (SRP) for H2 production. The activity tests for SRP were carried out in a fixed bed reactor (FBR) under different operating conditions. The NTZ-composite consisting of NiO/TiO2 loaded ZnTiO3 perovskite achieved the highest yield of H2 and phenol conversion of ~76 and 90%, respectively, with excellent durability and time on stream (50 h) stability without obvious deactivation. The high exposed active sites of NiO/TiO2 metals over the bi-metal support (ZnTiO3) and the metal-support interaction significantly improved the catalytic performance. The products distribution of H2, CO2, and CO as a measure of the dominant reactions; SRP, water gas shift (WGS), and reverse water gas shift (RWGS) were correlated to kinetic models and developed according to Langmuir-Hinshelwood-Hougen-Watson (LHHW) expressions. LHHW model accurately fitting the experimental results with surface reactions as the kinetic limitations. SRP reaction revealed the highest rate constant of 21.70 mol g-cat-1 h-1 atm-1 with 39.96 kJ mol-1 activation energy. NTZ is a promising catalyst for the SRP reaction toward H2 production with minimum kinetic limitations and would be promising in the clean energy production and other environmental applications
Ni-embedded TiO2-ZnTiO3 reducible perovskite composite with synergistic effect of metal/support towards enhanced H2 production via phenol steam reforming
No full text4Highly reducible Ni-dispersed TiO2-ZnTiO3 perovskite nanocomposite with different anatase/rutile contents of TiO2 for enhanced phenol steam reforming (PSR) towards selective H2 production has been investigated. In-situ growth of TiO2 nanoparticles (NPs) over ZnTiO3 cubic perovskite was obtained through hydrothermal assisted impregnation method. TiO2-ZnTiO3 composite performance was entirely dependent on the Zn/Ti molar ratios. With Zn/Ti molar ratio of 2, 19.80% TiO2 rutile phase in TiO2-ZnTiO3 composite was obtained, giving highest catalytic activity for H2 production. Using 10% Ni supported TiO2-ZnTiO3, phenol conversion and H2 yield of 89.10% and 75.60%, respectively were attained, while it was only 44.60% and 63.32% with 10% Ni/TiO2 NPs. This was obviously due to strong metal-support interaction with higher Ni-dispersion. More importantly, CO yield with Ni/TiO2 was 9.68%, decreased to 6.49% using 10% Ni/TiO2-ZnTiO3 perovskite composite, resulting in lower CO/CO2 ratio and trivial coke formation. Besides, Ni/TiO2-ZnTiO3 composite gave stability for more than 50 h without obvious deactivation, while it was only 6 h over Ni/TiO2 NPs. The effect of operating parameters reveals that reaction temperature 700 °C, catalyst loading 0.3 g and phenol/water ratio 5/95 wt% gave the highest catalyst activity. Besides, activity was also enhanced with increasing GHSV (mL.g−1.h−1), which confirms external mass transfer limitation. In conclusion, strong metal-supports interactions in Ni/TiO2-ZnTiO3 composite provide higher Ni-dispersion for stimulating catalytic activity and can be considered as a promising material for hydrogen production applications
In-situ growth of TiO2 imbedded Ti3C2TA nanosheets to construct PCN/Ti3C2TA MXenes 2D/3D heterojunction for efficient solar driven photocatalytic CO2 reduction towards CO and CH4 production
No full textConstructing efficient structured materials for artificial photosynthesis of CO2 is a promising strategy to produce renewable fuels in addition of mitigating greenhouse effect. In this work, 2D porous g-C3N4 (PCN) coupled exfoliated 3D Ti3C2TA MXene (TiC) nanosheets with TiO2 NPs in-situ growth was constructed in a single step through HF treatment approach. The different exfoliated TiC structures were successfully synthesized for adjusting HF etching time (24 h, 48 h and 96 h). With growing etchant time from 24 to 96 h, the amount of TiO2 produced was increased, but it has adverse effects on CO and CH4 production rate. The maximum production rates for CO and CH4 of 317.4 and 78.55 µmol g-1 h-1 were attained when the 10TiC-48/PCN was employed than using TiC-24/PCN, TiC-96/PCN and PCN composite samples, respectively. The performance of 10TiC-48/PCN composite for CO and CH4 evolution were 9.9 and 6.7 folds higher than using pristine PCN sample, respectively. The possible mechanism is assigned to porous structure with intimate contact enabling efficient charge carrier separation with the role of TiO2 NPs to work as a bridge to transport electrons towards MXene surface. Among the reducing agents, water was favorable for CO evolution, whereas, methanol–water system promoted CH4 production. All these findings confirm that heterojunction formation facilitates charges separation and can be further used in solar energy relating application
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