Dopants In Order Research Articles

Carbon nanotube fibers as efficient p- and n-type thermoelements within geopolymers: A route for large-scale thermal energy harvesting from building structures

This study reports for the first time, the thermoelectric (TE) performance of continuous p- and n-type carbon nanotube fiber (CNTF) filaments integrated within a sustainable, fine-grained geopolymer (GP) based concrete matrix for the complete replacement of cement with supplementary cementitious materials towards CO2 emissions reduction policy. Moreover, CNTF as CO2 negative, conductive, durable and lightweight material could multidimensionally contribute on the achievement of sustainability goals. Herein, pristine CNTF filaments were molecularly modified with p- and n-type aqueous-based dopants in order to stably tune their intrinsic semi-conducting properties via a facile and scalable dip-coating process. The achieved Seebeck coefficient values of the optimized p- and n-type CNTF were +45.2 μV/K and −38.4 μV/K, respectively. Thereafter, the p- and n-type CNTF filaments were employed as pillar-like thermoelectric elements incorporated within a GP mixture for the assembly of a structural thermoelectric generator (TEG) device. The obtained TEG-enabled GP-based concrete demonstrator comprising of 8 p-n serially interconnected junctions is capable of generating a power output of 0.3 μW at an applied through-thickness temperature gradient (ΔT) of 50 Κ. Subsequently, the experimental work was validated using coupled field of TE simulations. Self-powered infrastructures are forecasted to efficiently benefit from available ΔT on large-scale upon their operational lifetime, further promoting future net-zero energy consumption concepts.

Cobalt-substituted porous calcium copper titanate electrodes for paracetamol degradation by an electro-oxidation/peroxymonosulfate system

Developing cobalt-substituted perovskite electroactive membranes with an efficient Co/Cu combination mode is an important environmental challenge for removing drugs via peroxymonosulfate (PMS) activation. In this work, cobalt (Co)-substituted calcium copper titanatewas synthesized with an easy ball milling process and used as an anode in electro-oxidation in the presence of PMS for paracetamol degradation. The Co-CCTO anode with a Co ratio of 0.5 showed the highest removal efficiency (100 % of 10 ppm paracetamol after 180 min) due to the increase of the active sites and the appearance of the Co2+/Co3+ cycle that accelerates the charge transfer with Co incorporation into the lattice. Scavenger experiments showed that sulfate radicals (SO4̇−), oxygen radicals (O2̇-), hydroxyl radicals (̇OH), and singlet oxygen (1O2) were generated in the electro-oxidation-PMS reaction system and that SO4̇−, 1O2, and O2̇- were the dominant active radicals. The toxicity tests with Vibrio fischeri confirmed paracetamol mineralization and decomposition and the elimination of harmful by-products. It is crucial to explore the substitution of CCTO with different metal dopants in order to optimize the membrane performance and overcome the limitations associated with cobalt substitution.

Planar triangular lattice of the LuMgGaO4: Clustered site-occupancy and the upconversion luminescence of the co-doped Er,Yb ions

The ordered and stable structure of inorganic lattice is the basis of constructing high-efficiency rare earth activated fluorescence, solid-state laser or other optical materials. The mixed sensitized and activated rare earth ions usually keeps a uniform space-occupying and the energy transfer depends much on the doping concentration, while the aggregation of rare earth dopants in order is rare. In this work, a series of LuMgGaO4 phosphors were synthesized and the detail lattice parameters are analyzed through Vietveld refinement and the new CIF file is provided. The site-occupancy of Er3+, Yb3+ shows clustered features and the Er–Yb sublattice structure with various Yb/Er ratios were constructed on the basis of planar triangular lattice. The long-distance excitation energy migration to lattice or defects can be effectively inhibited in case of the hexagonal circle Er-6Yb sublattice, in which the most intense green/red UCL was obtained. All the results demonstrate the novelty of regulating ordered site-occupancy of rare earth ions on a compact planar triangular lattice with higher efficiency of energy migration, which will pave a way for developing phosphor-converted materials or laser materials with better performance.

Effects of Doping on Conduction/Densification of BaCe0.5fZr0.3Y0.2O3-Δ Electrolyte for Green Hydrogen Applications

For reaching the goal of 2050 net-zero carbon emission, the production of green H2 needs a very efficient and cost-effective approach. A proton-solid oxide electrolyzer cell (P-SOEC) based on BaCe0.5Zr0.3Y0.2O3-δ (BCZY) proton conducting electrolyte may show some advantages such as (1) Use of lower cost metals, alloys and coatings, (3) Ease of gas sealing, (4) Reduced cost of hydrogen production. BaCe0.5Zr0.3Y0.2O3-δ (BCZY) is known for its unique stability and high proton conduction properties due to the doping effect from the substitution of Zr and Y for Ce ions. For better performance of P-SOEC, a solid electrolyte with good densification to prevent the direct mixing of fuel and oxidant is essential.Thus, the objective of this study is to develop a cost-effective process with proper dopant in order to obtain well-densified BCZY at a temperature as low as 1200°C. For undoped BCZY, much less densification was observed. With the addition of proper dopant, BCZY may reach 97% relative density at the same temperature. It is believed that the presence of liquid phase is the reason for densification enhancement of doped BCZY. The affected electrical and structural properties will be analyzed and discussed based on sintering theory and kinetics. The crystal structure and microstructure of sintered BCZY was also characterized using XRD, field-emission SEM, and STEM.

Indium tin oxide nanoparticles induced molecular rearrangement in nematic liquid crystal material

In the present article, we report the influence of indium tin oxide (ITO) nanoparticles (NPs) on the macroscopic molecular arrangement of a nematic liquid crystal (NLC) material namely 4 cyano-4ʹ-pentylbiphenyl (5CB). To achieve the objective, we have adopted various concentrations (0.25, 0.5 and 1 wt%) of ITO NPs in 5CB and filled them in the homogeneously aligned sample cells to observe their influence on the dielectric and optical texture of the NLC under investigation. Firstly, polarizing optical micrographs under crossed polarizers were recorded to observe the uniform dispersion and miscibility of ITO NPs in the nematic phase of 5CB. These micrographs also infer the molecular rearrangement of 5CB material that is occurred under the simultaneous and cumulative anchoring effect induced by ITO NPs and aligning layers. Furthermore, the dielectric parameters (permittivity, loss and dielectric loss factor) of pristine and composites as the function of frequency, temperature and DC biasing have been studied. Surprisingly, dielectric permittivity and relaxation frequency of 0.25 wt% ITO NPs composite was found to be the maximum that is decreased with further increment in the concentration of ITO NPs. We have also confirmed the thermal stability of 0.25 wt% ITO NP-induced changes in 5CB. Apart from it, by virtue of temperature-dependent dielectric anisotropy and optical textures, we have reported a significant decrement (∼14 %) in clearing temperature of 5CB. These results will pave the way to devise a system with ITO NPs as the dopant in order to obtain desired phase transition temperature of liquid crystal materials.

Doped silica sol layer coatings on evanescent field fiber Bragg gratings for optical detection of nitroaromate based explosives

Evanescent field etched fiber Bragg gratings (eFBG) were prepared with doped and non-doped nanoporous silica sol coatings for optical detection of the nitroaromatic explosives 2,4-dinitrotoluene (DNT), 1,3-dinitrobenzene (DNB) and trinitrotoluene (TNT). We used 3-aminopropyltrimethoxysilane (APTMS) and tetrabutylammonium hydroxide based receptors (TBAH, C16H37NO) as dopants in order to increase the specific identification of the nitroaromates. In nitroaromatic trace gas atmosphere the induced wavelength shift of the Bragg reflection signal was highest for the sensor with TBAH-doped silica sol receptor coating. Within the first two minutes during exposure the change of the signal intensity, reflecting the adsorption dynamics of the nitroaromatic explosives, was most significant and characteristically depending on the type of receptor dopant used. The cross sensitivities of the sensor with TBAH-doped silica sol receptor coating with four common solvents like acetone, ethanol, 2-propanol and tetrahydrofuran (THF) in comparison to the sensitivity of the tested explosives was more than six orders of magnitude (106) lower than that of solvents, indicating a very high selectivity of the sensor. By applying a simplified diffusion model correlated to a series of measurements with different distances to the target we estimated the limit of detection for a sensor coated with TBAH doped silica sol with 35.8 ± 0.9 ppb for DNB and 140.2 ± 1.8 ppb for DNT in air at room temperature. Using a more etched FBG (but mechanically less robust) sensor we were able to detect TNT as well at concentrations about 5 ppb at room temperature in air. A major result of our investigations was to demonstrate, that the nanoporous silica sol host matrix is suited for fast adapting with low technological effort the affinity of the receptor coating for silica-based evanescent field sensors. For future applications a set of sensors of silica-sol coatings with different dopants in combination with pattern recognition of the sensor signals could be used for clear identification of explosives.

N-Type doping of a solution processed p-type semiconductor using isoelectronic surface dopants for homojunction fabrication

The p-n junction is one of the fundamental requirements for a practical semiconductor-based electronic device. Designing a heterojunction comprising of dissimilar p-type and n-type semiconductors calls for careful energy level considerations, both when selecting the semiconductor materials as well as the metal contacts. A homojunction based on a single semiconductor simplifies this task, as energy levels of the p-type and n-type materials are already fairly similar, allowing for easier selection of contacts. Traditionally, homojunctions rely on doping of a bulk semiconductor to achieve p- and n-type transport through controlled addition of aliovalent dopants via energy-intensive processes such as ion implantation or thermal annealing. Exact control of doping in nanocrystalline semiconductors is significantly more challenging, due to self-purification effects. However, owing to their large surface areas, surface moieties can be utilized to both dope the nanostructures as well as tune their energy levels. In this report, we present a facile technique based on an isoelectronic surface dopant in order to achieve p- and n-type materials based on the same semiconductor. We show that thin p-type colloidal Bi2Te3 nanowires can be switched to n-type through surface functionalization, thus increasing the availability of new nanocrystalline solution-processable p-n homojunctions.

Side-Chain Engineering of Diketopyrrolopyrrole-Based Hole-Transport Materials to Realize High-Efficiency Perovskite Solar Cells.

The design and synthesis of a stable and efficient hole-transport material (HTM) for perovskite solar cells (PSCs) are one of the most demanding research areas. At present, 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-MeOTAD) is a commonly used HTM in the fabrication of high-efficiency PSCs; however, its complicated synthesis, addition of a dopant in order to realize the best efficiency, and high cost are major challenges for the further development of PSCs. Herein, various diketopyrrolopyrrole-based small molecules were synthesized with the same backbone but distinct alkyl side-chain substituents (i.e., 2-ethylhexyl-, n-hexyl-, ((methoxyethoxy)ethoxy)ethyl-, and (2-((2-methoxyethoxy)ethoxy)ethyl)acetamide, designated as D-1, D-2, D-3, and D-4, respectively) as HTMs. The variation in the alkyl chain has shown obvious effects on the optical and electrochemical properties as well as on the molecular packing and film-forming ability. Consequently, the power conversion efficiency (PCE) of the PSC under one sun illumination (100 mW cm-2) is shown to increase in the order of D-1 (8.32%) < D-2 (11.12%) < D-3 (12.05%) < D-4 (17.64%). Various characterization techniques reveal that the superior performance of D-4 can be ascribed to the well-aligned highest occupied molecular orbital energy level with the counter electrode, the more compact π-π stacking with a higher coherence length, and the excellent hole mobility of 1.09 × 10-3 cm2 V-1 s-1, thus providing excellent energetics for effective charge transport with minimal charge-carrier recombination. Furthermore, the addition of the dopant Li-TFSI in D-4 is shown to deliver a remarkable PCE of 20.19%, along with a short-circuit current density (JSC), open-circuit voltage (VOC), and fill factor (FF) of 22.94 mA cm-2, 1.14 V, and 73.87%, respectively, and superior stability compared to that of other HTMs. These results demonstrate the effectiveness of side-chain engineering for tailoring the properties of HTMs, thus offering new design tactics to fabricate for the synthesis of highly efficient and stable HTMs for PSCs.

Effect of zeolite content on proton conductivity and technical characteristics of the membranes based on crosslinked polyvinyl alcohol

Polyvinyl alcohol (PVA)-based ion-exchange membranes are a promising group of materials for use in solid polymer fuel cells (SPFC) due to their high hydrophilicity, film forming ability, low cost, good mechanical properties and the possibility of crosslinking PVA with various chemicals. The compounds with a carboxyl or carbonyl functional group, such as polybasic acids and their anhydrides, were used as crosslinking agents resulting in the formation of a gel. Cross-linking reagents may contain ionic groups, for example, sulfonic, inducing the proton conductivity of PVA in membranes. Ceramic materials based on the oxides of aluminum, silicon, titanium, tin, zirconium, etc. serve as dopants in order to improve the technical characteristics of such membranes, such as to increase ionic conductivity, chemical and thermal stability, as well as the mechanical strength of the membranes. In this work, we report on the preparation of new biodegradable proton exchange membranes for SPFCs based on of polyvinyl alcohol crosslinked with sulfosuccinic acid and doped with beta zeolite particles. The content of zeolite in the composition of the membranes was varied from 1 to 25 %. The effect of the zeolite content on proton conductivity, ion-exchange capacity, moisture content, swelling coefficient, fuel (methanol) permeability and mechanical properties of membranes was studied. An increase in zeolite content from 1 to 25 % leads to an increase in the ion-exchange capacity of membranes from 1.5 to 2.9 mmol/g, a decrease in moisture content from 38 to 28 % and a methanol permeability from 2.27  10 -6 to 6.91  10 -7 cm 2 s -1 . The temperature dependence of the proton conductivity of composite membranes in the range from 30 to 80 oC at the relative humidity of 100 % was studied. The highest value of electrical conductivity was demonstrated by a membrane containing 25 % of BEA zeolite, whose proton conductivity was 23.2 mS·cm -1 .

Small Host–Guest Systems in the Gas Phase: Tartaric Acid as a Host for both Anionic and Cationic Guests in the Atmospheric Pressure Chemical Ionization Source of Ion Mobility Spectrometry

The ionization of tartaric acid (TA) in an atmospheric pressure chemical ionization corona discharge ion source was studied by ion mobility spectrometry (IMS) with zero air as the drift gas. Density functional theory was used for structural and thermodynamic analyses of the produced ionic clusters. Ion mobility spectra of TA were recorded in both positive and negative modes of CD with and without ammonia and chloroform as dopants in order to produce NH4+ and Cl-, respectively, as the reactant ions (RIs). In the absence of these dopants, the RIs were mainly H3O+ and O2- in the positive and negative CD, respectively. TA solutions in water and methanol were injected into the ionization region of the IMS instrument, and the product cations TA·H+(H2O)n, TA·H+(CH3OH), TA·NH4+, and TA·NH4+(CH3OH) were observed in the positive CD. Anionic clusters (TA-H)-, (TA-H)-·CH3OH, (TA-H)-·TA, TA·Cl-, and (TA)2Cl- were produced in the negative CD. The anions TA·Cl- and (TA)2Cl- were not produced in an air atmosphere, and we observed their peaks when pure oxygen was used as the drift gas. Optimized structures of the clusters showed that TA·NH4+, TA·Cl-, and (TA)2Cl- are small host-guest systems in the gas phase, with TA as a host. (TA)2Cl- is a weakly bonded complex (an anion-bound dimer) that was observed at atmospheric pressure. The proton-bound dimer TA·H+·TA was not produced in the positive CD, while the anionic dimer (TA-H)-·TA was observed in the negative CD. This phenomenon was interpreted on the basis of the hydration of TA·H+ and (TA-H)-.

Photoluminescence of Doped YAG Transparent Ceramics Fabricated by Spark Plasma Sintering

AbstractDoped transparent ceramics have potential for a wide range of optical applications derived from their easily controllable fluorescence properties. The aim of this contribution is to present and discuss an effective fabrication method for doped transparent yttrium aluminum garnet ceramics. The powder synthesis route was adapted from common co‐precipitation methods and the powder densification was performed by spark plasma sintering. Parameters of the fabrication process were optimized for different lanthanide dopants in order to obtain highly transparent single‐ and multi‐doped ceramics. The photoluminescence properties of the samples were measured and discussed. The use of lithium fluoride as a sintering additive was confirmed to be favorable and post‐sintering heat treatments were shown to be necessary for certain dopants. Finally, the photoluminescence lifetime of dopants in a multi‐doped sample were measured and the energy transfer efficiency between dopants was determined.

MgO or Al2O3 crucible: Which is better for the preparation of LLZ-based solid electrolytes?

Lithium lanthanum zirconate (Li7La3Zr2O12, LLZ) solid electrolytes were usually prepared by using Al2O3 crucibles and/or Al3+ dopants in order to stablize the formation of cubic garnet phase. In this work, we argue that Al-free MgO crucible could be better for the preparation of LLZ-based solid electrolytes through a detailed comparison of LLZ-Ga0.2 samples prepared respectively by using MgO and Al2O3 crucibles. The solid-state reaction method was firstly used to prepare Li7-3xGaxLa3Zr2O12 (x = 0–0.4) pellets by using Al-free MgO crucibles, which were sintered at 1100 °C for 12 h. The highly conductive cubic phase was obtained at Ga3+ doping content as low as x = 0.05 and the highest room-temperature conductivity was obtained at x = 0.2. Al2O3 crucible was then used to prepare the LLZ-Ga0.2 pellet for comparing the influence of these two different crucibles. The results show that a higher lattice parameter (a = 12.9762 (8) Å), a higher relative density (95.5%) and a higher room-temperature ionic conductivity (1.352 (3) mS/cm) were achieved by using the MgO crucible.

Fabrication of Calcium Doped PlSZT Ceramics using High Planetary Mill Method

Ca-doped modified Lead Lanthanum Strontium Zirconium Titanate (PLSZT) ceramic, was synthesized with different concentrations of dopant in order to enhance the properties of PZT. Calcium carbonate, CaCO3 have been used as a source of Ca dopant in the preparation of PCLSZT using high planetary ball mill, palletized and sintered at 1200 °C for 3 hours. The uses of high planetary milling benefit in shorten the time for powder preparation where the calcination was not required. The concentration of CaCO3 was varied from 0.01, 0.03, 0.05 and 0.10 mol% and their effects on phase formation, surface morphology, density and porosity have been studied using X-ray diffraction (XRD) and Scanning electron microscopy (SEM). XRD results showed that all Ca-doped PLSZT samples present a tetragonal phase. Whereas SEM results showed that the grain size of the samples was increased with increasing calcium concentration. In addition, the density was observed to be decreased with increasing amount of Ca concentrations.

Co-, Cu- and Fe-Doped Ni/Al2O3 Catalysts for the Catalytic Decomposition of Methane into Hydrogen and Carbon Nanofibers

The catalytic decomposition of methane (CDM) process produces hydrogen in a single stage and avoids CO2 emission thanks to the formation of high added value carbon nanofilaments as a by-product. In this work, Ni monometallic and Ni–Co, Ni–Cu, and Ni–Fe bimetallic catalysts are tested in the CDM reaction for the obtention of fishbone carbon nanofibers (CNF). Catalysts, in which Al2O3 is used as textural promoter in their formulation, are based on Ni as main active phase for the carbon formation and on Co, Cu, or Fe as dopants in order to obtain alloys with improved catalytic behaviour. Characterization of bimetallic catalysts showed the formation of particles of Ni alloys with a bimodal size distribution. For the doping content studied (5 mol. %), only Cu formed an alloy with a lattice constant high enough to be able to favor the carbon diffusion through the catalytic particle against surface diffusion, resulting in higher carbon formations, longer activity times, and activity at 750 °C; whereas Ni, Ni–Co, and Ni–Fe catalysts were inactive. On the other hand, Fe also improved the undoped catalyst performance presenting a higher carbon formation at 700 °C and the obtention of narrow carbon nanofilaments from active Ni3Fe crystallites.

The enhanced piezoelectric property of (Li,K,Na)(Nb,Ta)O3 lead-free ceramics induced by rare earth oxide doping

The ions doping engineering has already been proved to be an effective approach of adjusting the intrinsic properties of perovskite structured materials and even realizing some new functionality. The polymorphic phase transition effect was put forward to elucidate the enhanced ferroelectric and piezoelectric properties in (K,Na)NbO3-based materials. In current research, Li-Ta modified (K,Na)NbO3 lying in composition region of the coexistence structure was selected as target materials, and Ce2O3 was chose as dopant in order to reveal the effect of ion doping on the target materials. Owing to the sensitive energy state in the coexistence phase structure, an obvious phase evolution from orthorhombic to tetragonal would be brought about by the doping of Ce2O3. When the doping amount was 0.5% mol, the enhanced ferroelectric property (the remnant polarization of Pr = 21.8 μC/cm2), piezoelectric property (the piezoelectric coefficient of d33 = 272 pC/N) and field-induced property (0.13@4 kV/mm) could be achieved.

Tunable Synthesis of Colorful Nitrogen-Doped Titanium Oxide and Its Application in Energy Storage

The one-pot synthesis of titania with diverse degrees of oxygen vacancies and nitrogen dopants through arc-discharge and nitridation process is first reported. The series of TiO2–x:N samples are prepared by tuning the ratio of CO2/H2 in the chamber. The chemical composition, microstructure, and valence state of TiO2–x:N are characterized by a variety of measurements. Specifically, the as-prepared samples achieve the highest specific capacitance (210 F g–1 at 2 mV s–1), which is much higher than that of TiO2–x and commercial P25. Moreover, it exhibits good cycling stability with 9% attenuation of capacitance after 10,000 cycles. The capacitive enhancement can be attributed to more active pseudocapacitive properties and improved electrical conductivity due to oxygen vacancies and nitrogen dopants. This work provides another feasible path to simplify the tunable synthesis of titania with different oxygen defects, and further optimize the degree of nitrogen dopants in order to realize better performance in the future.

Conflicting effect of chemical doping on the thermoelectric response of ordered PEDOT aggregates.

Poly(3,4-ethylenedioxythiophene) (PEDOT) semiconductor plays a relevant role in the development of organic thermoelectric (TE) devices for low-power generation. While dopant counterions are usually needed to provide electrical conductivity, their overall effects on the thermoelectric response of the systems are unknown and uncontrolled. Here, we present a first principles study of the electronic and thermal transport of PEDOT crystalline assemblies, specifically analysing the role played by tosylate dopants on the thermoelectric figure of merit of the doped system. Our results demonstrate that, beside the desired charging effect, the presence of dopants impacts the bulk configuration by inflating the packing structure and worsening the intrinsic transport properties of the PEDOT host. This provides a rationale for the necessity of controlling the optimal amount and the structural incorporation of dopant in order to maximize the thermoelectric response of organic materials.

Mechanism of Enhanced Sulfur Tolerance on Sm-Doped CeO2: A Density Functional Study

In this presentation, using first-principles calculation, the function of samarium (Sm) 4f states and Sm-perturbed O 2p states in enhancing the sulfur tolerance of Sm-doped CeO2 was elucidated. We find that the sulfur tolerance of Sm-doped CeO2 is closely related to the modification of O 2p states by the strong interaction between Sm 4f and O 2p states. In particular, the availability of unoccupied O 2p states near the Fermi level is responsible for enhancing the sulfur tolerance of Sm-doped CeO2 compared to the pure CeO2[1]. To better understand the importance of unoccupied O 2p states, the effect of various 4f shell dopants (Pr, Pm, and Eu) on the activity of surface lattice oxygen are also investigated. This work also hints on the importance of properly engineering the activity of oxygen ion in CeO2-based materials by adding dopant in order to develop sulfur-tolerant solid oxide fuel cell anode. [1] DH Lim, HS Kim, SP Yoon, J Han, CW Yoon, SH Choi, SW Nam, and HC Ham, Physical Chemistry Chemical Physics 16 (22), 10727-10733, (2014)

Sc and Nb dopants in SrCoO3 modulate electronic and vacancy structures for improved water splitting and SOFC cathodes

SrCoO3 is a promising material in the field of electrocatalysis. Difficulties in synthesising the material in its cubic phase have been overcome by doping it with Sc and Nb ions [Mater. Horiz.2015, 2, 495–501]. Using ab initio calculations and special quasi random structures we undertake a systematic study of these dopants in order to elucidate the effect of doping on electronic structure of the SrCoO3 host and the formation of oxygen vacancies. We find that while the overall electronic structure of SrCoO3 is preserved, increasing the Sc fraction leads to a decrease of electrical conductivity, in agreement with earlier experimental work. For low Sc and Nb doping fractions we find that the oxygen vacancy formation increases relative to undoped SrCoO3. However, as the dopants concentration is increased the vacancy formation energy drops significantly, indicating a strong tendency to accommodate high concentration of oxygen vacancies and hence non-stoichiometry. This is explained based on the electronic instabilities caused by the presence of Sc ions which weakens the B-O interactions as well as the increased degree of electron delocalization on the oxygen sublattice. Sc dopants also shift the p-band centre closer to the Fermi level, which can be associated with experimentally reported improvements in oxygen evolution reactions. These findings provide crucial baseline information for the design of better electrocatalysts for oxygen evolution reactions as well as fuel-cell cathode materials.

Effects of oxidant and dopants on the properties of cellulose/PPy conductive composite hydrogels

ABSTRACTCellulose/Polypyrrole (PPy) composite hydrogels were prepared by in situ chemically oxidative polymerization of pyrrole in the cellulose matrix. Ferric chloride (FeCl3) was used as an oxidant and four sulfonic compounds were used as dopants in order to investigate the effects on the properties of cellulose/PPy conductive composite hydrogels. The extent of polymerization of PPy was determined by the amount of the oxidant and the composite hydrogels with oxidant at 0.3M−0.5M exhibited the higher conductivities for the intrachain and interchain conductivities of conductive polymers; the fracture stress of the composite hydrogels could be up to 26.25 MPa with a strain of 86.8% when the oxidant was at 0.5M. Doping is an efficient way to improve the conductivity of the composite hydrogels and four kinds of dopant were compared in this work. Long alkane chain and side group in dopants can increase the steric hindrance of PPy polymerization which resulted in the lower conductivity of the composite hydrogels compared to dopants with smaller steric hindrance. The conductivity of the composite hydrogel firstly increased and then decreased with the concentration of dopants from 0.1M to 1.0M in this work. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43759.