We herein report a fascinating carbon aerogel that has a unique framework structure consisting of one-dimensional (i.e. nanofibers) and two-dimensional (i.e. graphene) carbon nanomaterials. Such a ...carbon aerogel was prepared by carbonization of electrospun polyacrylonitrile with graphene oxide sheets (GO). The nanofiber-graphene interconnection within the aerogel considerably enhances the electrochemical characteristics. The aerogel showed an electrosorption capacity of 15.7 mg g−1 in 500 mg L−1 NaCl solution, and the CDI cell exhibited stable performance over 100 cycles. Moreover, the carbon aerogel has good electrical conductivity and faster electron transfer rate. Such a cross-linked porous aerogel may provide a new strategy for highly efficient CDI applications.
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•A fascinating carbon aerogel with 3D layered porous structure is fabricated via electrospinning, freeze-shaping and carbonization.•Novel structures and electrochemical properties of the electrodes are tested.•The obtained carbon aerogel has good electrical conductivity and faster electron transfer rate.•The obtained carbon aerogel exhibits extraordinary electrochemical characteristics and a high electrosorption capacity.
Pd-Based catalysts are considered the most efficient catalysts in direct formic acid fuel cells. However, the poisoning and dissolution of Pd in acidic systems limit its commercialization. Here, we ...propose an all-in-one solution for the anti-dissolution and anti-poisoning properties of palladium. A novel structured catalyst, Pd nanoparticles embedded in a carbon layer internally decorated with tourmaline nanoparticles (TNPs), is proposed for formic acid oxidation (FAO). The internal electric field strength of the catalysts is readily regulated by controlling the amount of TNPs. Remarkably, the prepared catalyst exhibits as high as 3.9 times mass activity (905 A g
−1
) compared with the commercial Pd/C catalyst. The significant improvement in the electrocatalytic performance of the catalyst is mainly due to the polarized electric field of TNPs causing charge transfer from Pd to tourmaline, which weakens the O-H bond of HCOOH and the bond between Pd and CO
ad
. Another advantage brought by the internal polarized electric field is that it facilitates water dissociation to produce OH
ad
, thereby improving the anti-poisoning ability of the catalyst in acidic media. Moreover, the firmly anchored Pd nanoparticles can avoid dissolution and agglomeration during long-term use. 80.2% mass activity remained after the accelerated durability test.
By regulating the internal electric field of the catalyst, the strain effect and ligand effect of Pd nanoparticles are induced to weaken the Pd-CO
ad
bond strength and promote the formation of OH
ad
.
•In-situ pyrolysis is used to dope N in carbon matrix and reduce Pd2+ simultaneously.•Core-shell structured N-doped carbon encapsulated Pd nanoparticles are synthesized.•Pd is reduced from Pd2+ by ...the complexed N in 2,2′-bipyridine during the pyrolysis.•Pd-N complexes and charge transfer from carbon layer to Pd are observed in Pd@NxC.•In-situ pyrolysis method can be applied to carbon supports with different geometry.
Doping nitrogen (N) into the carbon support was widely applied to enhance the performance of Pd toward formic acid electro-oxidation (FAO). However, traditional nitrogen doping methods can only introduce a low content of nitrogen as well as a two-step complicated procedure to synthesize catalysts. In this study, a facile one-pot strategy is demonstrated to prepare N-doped carbon encapsulated palladium nanoparticles (Pd@NxC) via the pyrolysis of 2,2′-bipyridine palladium (II) complexes. A N-doped carbon layer with the thickness of about 4 nm is in-situ generated over Pd nanoparticles by only one pyrolysis procedure. Both XPS and in-situ XRD results suggest that metallic Pd is reduced from Pd2+ by the complexed N in bipyridine during the pyrolysis at high temperature. The physical characterizations prove that the in-situ formation of N-doped carbon shell can not only effectively prevent the agglomeration or dissolution of Pd nanoparticles, but also promote the charge donation from the carbon layer to Pd, and maintain the structure of Pd atom complexed to two pyridinic-N atoms (Pd-N). This in-situ synthesis strategy can be successfully applied to carbon supports with different geometry, such as reduced graphene oxide and Vulcan XC-72. Pd@N3C/rGO, which contains the highest amount of N (7.39 at.%) and Pd-N (33.15%), shows the highest specific activity (5.88 mA cm−2) and excellent durability toward FAO.
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•A simple four-step method to prepare T-Nb2O5/CNTs composite.•The composite is with well-dispersed CNTs in the Nb2O5 phase.•The composite has excellent large-current discharge ...property.•The composite has a high energy storage property at high current density.
In this paper, we report a facile template-free method to prepare the T-Nb2O5/CNTs composite. The addition of ammonia induces the electrostatic interaction between functionalized CNTs and niobic acid colloids during hydrothermal process, resulting in CNTs homogeneously distributed in the T-Nb2O5 phase. The obtained T-Nb2O5/CNTs composite shows high rate Li+ storage ability with typical intercalation capacitive behaviour. The presence of well-dispersed CNTs in Nb2O5 can apparently reduce the limitation from diffusion process and increase the high rate charge-discharge capability. From the galvanostatic tests, a capacity of ∼180mAhg−1 at 1Ag−1 and ∼130mAhg−1 at 5Ag−1 is attained.
Abstract
In order to reduce the impact of load fluctuation brought by new energy interconnection, the operation cost of power grid is increased. Considering the characteristics of load fluctuation, ...this paper studies a new energy grid source load interval coordination scheduling method. Based on the characteristics of source load fluctuation and demand side load fluctuation of new energy grid, the dispatching principle is established. In this paper, the flexible operation region of new energy grid is calculated, and the target function of power grid source load interval is constructed. Numerical results show that the proposed method can improve the economy of energy storage unit and power system, and the comprehensive benefit is positive in different scenarios.
The large-scale connection of the renewable energy with random and fluctuating output of the grid has a serious impact on the safe and stable operation of the grid. Considering the high cost of ...energy storage and the fluctuation of load, in this study, an optimization approach for designing the distribution network’s energy storage capacity is presented. This paper analyzes the uncertainty of new energy, and constructs a single distribution network energy storage station model based on the analysis results. In this paper, the typical daily total network loss is taken as the objective function for site selection and capacity planning. In this paper, particle swarm optimization algorithm is used to optimize the energy storage and capacity planning of distribution network. The experimental results show that this method can reduce the operating cost of distribution network and restrain the system load fluctuation. This method optimizes the economy and reliability of distribution network system.
Electrode materials with high electrosorption capacity and stable cycling performance are desired by the capacitive deionization (CDI) process. A novel CDI electrode is prepared by developing the ...nitrogen-doped porous carbon tubes composite (PCT-N) material. It consists of interconnected tubular network construction and hierarchical porous structure. The electrospun polyacrylonitrile/zinc acetate (PAN/Zn(Ac)2) nanofibers coated with a layer of zeolitic imidazolate framework (ZIF, a subfamily of metal-organic frameworks) nanocrystals are used as precursors for carbonization. The prepared PCT-N material has high nitrogen-doping amount and hollow macroporous structure with lateral mesopores. It has advantages of excellent electrical conductivity, higher specific surface area and larger total pore volume. The material exhibits a salt adsorption capacity of 16.7 mg g−1 in 500 mg L−1 initial NaCl solution, and shows good cycle stability over 100 cycles. Such a PCT-N electrode provides a promising alternative candidate for developing CDI technology.
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•Interconnected tubular porous carbon with nitrogen-doping are prepared from the core-shell composite nanofibers.•The formation mechanism and influence factors of the hierarchical porous structure are proposed.•The obtained electrodes exhibit great electrochemical characteristic and high electrosorption performance.
•Pd/BTOHx@NCy with strength-regulated polarized electric field is synthesized.•The electric field is provided by BaTiO3 and regulated by carbon shell thickness.•Carbon shell promotes charge transfer ...during FAO and excludes electronic effect.•The optimized electric field strength leads to high FAO catalytic performance.•COad is removed by the pyroelectric effect induced by the temperature change.
To solve the severe problem of environmental pollution, the demand for commercial applications of direct formic acid fuel cell (DFAFC) has significantly increased. Designing electrocatalysts with high anti-poisoning ability and activity for formic acid electrooxidation (FAO) is the key for the development of DFAFC. Utilizing polarized electric field is a new attempt to improve catalytic performance as it can adjust the adsorption energy of reactants or intermediate species on the catalysts. In this work, pyroelectric material BaTiO3 (BTOH), which generate polarized electric field, was introduced for FAO for the first time. A series of core–shell structured Pd/BTOHx@NCy catalysts was synthesized with BTOH as the core, nitrogen-doped carbon as the shell, and palladium nanoparticles as the active sites. Among all catalysts, Pd/BTOH1@NC0.5 with the optimal carbon shell thickness of 4.6 nm owns the highest FAO catalytic activity and anti-poisoning ability because the carbon layer regulates the electric field strength to optimize the palladium surface adsorption energy. The study excluded the influence of electronic effect and revealed the effect of polarized electric field strength on the FAO activity and anti-poisoning ability through changing the thickness of carbon shell. In addition, the alternating cold-hot excitation experiments demonstrated that the polarized electric fields can effectively remove the poisoned substance on the surface of palladium. This study guides a new strategy to design electrocatalysts for FAO.
•Pd/TNP@SC with electric field and far-infrared radiation of tourmaline is prepared.•Pd/TNP@SC owns great FAEO activity and CO-tolerance than that of TNP-free catalyst.•Tourmaline leads to small Pd ...NPs, weak Pd-O bond, and easy molecule migration.•Dissociated OHadfrom water by electric field spontaneously convert COad into CO2.•Interaction between pPd NPs and OHad at the positive pole of TNP/SC is a key factor.
Palladium is the most effective catalyst with high initial activity for formic acid electrooxidation (FAEO) in direct formic acid fuel cells (DFAFCs), but the low performance of DFAFC comparing to H2-PEMFC and the accumulation of COad poisoning species on palladium restrict the commercialization of DFAFC. Herein, a novel and efficient FAEO catalyst, tourmaline modified Pd (Pd/TNP@SC) are prepared. A class of core@shell structured carbon coated tourmaline (TNP@SC) are equipped as the catalyst support to efficiently utilize the spontaneous polarization-induced electric field and far-infrared radiation of tourmaline for FAEO reaction. Physical and electrochemical measurements suggest that the existence of electric field and far-infrared radiation of tourmaline promote synthesizing smaller Pd nanoparticles, weakening the Pd-O bond, increasing molecular vibration and migration rate, and dissociating water molecules into OHad to spontaneously convert COad into CO2. Even under potentials applied higher than 0.3 V (vs. Ag/AgCl), Pd/TNP@SC catalysts still have high FAEO activity. Among all the Pd/TNP@SC catalysts investigated in this study, Pd/TNP@SC-800 owns the strongest electric field and far-infrared radiation, exhibits the best activity for FAEO, which is 3.1 times higher than that of tourmaline-free catalyst (Pd/SC)), and excellent CO-tolerance during FAEO reaction. This work provides an effective catalyst design strategy for FAEO.
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Adjusting the adsorption energy of adsorbates on catalyst can directly regulate the catalytic performance and reaction pathways of heterogeneous catalysis. Herein, we report a novel strategy, ...introducing polarization-induced electric field (PIEF) with different directions, to manipulate the adsorption energy of intermediates and reaction pathway of formic acid electrooxidation on Pd. Tourmaline nanoparticles are applied as the PIEF provider, of which the direction is successfully controlled via aligning the dipoles in tourmaline in a strong external electric field. Experimental and theoretical results systematically reveal that positive PIEF leads to an electron-deficient state of Pd, reduced adsorption energy of CO
ad
, enhanced adsorption energy of *HCOOH and *OH, and promoted formate pathway of formic acid electrooxidation. Pd/TNP+/FTO, with the aid of positive PIEF, shows threefold enhancement in the formic acid electrooxidation (4.74 mA·cm
−2
) with high durability and anti-poisoning ability compared with pristine Pd. This study leads a new route to design formic acid electrocatalysts and provides an understanding on how to control the adsorption energy of adsorbates on electrocatalysts by an internal electric field.
