Boosting the Ni-Zn interplay via O/N dual coordination for high-efficiency CO_(2) electroreduction

Design of supportive atomic sites with a controllably adjusted coordinating environment is essential to advancing the reduction of CO_(2) to value-added fuels and chemicals and to achieving carbon neutralization.Herein,atomic Ni(Zn)sites that are uniquely coordinated with ternary Zn(Ni)/N/O ligands were successfully decorated on formamide-derived porous carbon nanomaterials,possibly forming an atomic structure of Ni(N_(2)O_(1))-Zn(N_(2)O_(1)),as studied by combining X-ray photoelectron spectroscopy and X-ray absorption spectroscopy.With the mediation of additional O coordination,the Ni-Zn dual site induces significantly decreased desorption of molecular CO.The NiZn-NC decorated with rich Ni(N_(2)O_(1))-Zn(N_(2)O_(1))sites remarkably gained>97%CO Faraday efficiency over a wide potential range of -0.8 to -1.1 V(relative to reversible hydrogen electrode).Density functional theory computations suggest that the N/O dual coordination effectively modulates the electronic structure of the Ni-Zn duplex and optimizes the adsorption and conversion properties of CO_(2) and subsequent intermediates.Different from the conventional pathway of using Ni as the active site in the Ni-Zn duplex,it is found that the Ni-neighboring Zn sites in the Ni(N_(2)O_(1))-Zn(N_(2)O_(1))coordination showed much lower energy barriers of the CO_(2) protonation step and the subsequent dehydroxylation step.

Efficient CO_2 capture on low-cost silica gel modified by polyethyleneimine

In this work, a series of polyethyleneimine （PEI） functionalized commercial silica gel were prepared by wet impregnation method and used as CO2 sorbent. The as-prepared sorbents were characterized by N2 adsorption, FT-1R and SEM techniques. CO2 capture was tested in a fixed bed reactor using a simulated flue gas containing 15.1% CO2 in a temperature range of 25-100 ~C. The effects of sorption temperature and amine content on CO2 uptake of the adsorbents were investigated. The silica gel with a 30 wt% PEI loading manifested the largest CO2 uptake of 93.4 mgcoz/gadsorbent （equal to 311.3 mg^oz/gPEI） among the tested sorbents under the conditions of 15.1% （v/v） CO2 in N2 at 75 ~C and atmospheric pressure. Moreover, it was rather low-cost. In addition, the PEI-impregnated silica gel exhibited stable adsorption-desorption behavior during 5 consecutive test cycles. These results suggest that the PEI-impregnated silica gel is a promising and cost-effective sorbent for CO2 capture from flue gas and other stationary sources with low CO2 concentration.

Amorphous Se species anchored into enclosed carbon skeleton bridged by chemical bonding toward advanced K-Se batteries

Potassium-selenium(K-Se)batteries have attracted significant attention as one of the most promising alternatives of lithium-ion storage systems owing to high energy density and low cost.In the design of Se-based cathode materials,however,the low utilization rate of active Se and the rapid dissolution of polyselenides seriously weaken the capacity and cycle stability.Therefore,how to make full use of Se species without loss during the charge and discharge process is the key to design high-performance Se-based cathode.In this paper,a 3 D"water cube"-like Se/C hybrid(denoted as Se-O-PCS)is constructed with the assistance of Na_(2)CO_(3) templates.Thanks to the abundant carbonate groups(CO_(3)^(2-))originated from the Na_(2)CO_(3) templates,the molten Se species are firmly anchored into the pore of carbon skeleton by strong C-O-Se bonding.Thus,this unique Se-O-PCS model not only improves the utilization of active Se species,but also can reduce the contact with the electrolyte to inhibit the shuttle effect of polyselenides.Moreover,flexible carbon skeleton gives Se-O-PCS hybrid a good electrical conductivity and excellent structural robustness.Consequently,the resultant Se-O-PCS hybrid is endowed with an obviously enhanced K-ions storage property.

Dry-gel synthesis of hierarchical Ni-La@S-1 catalysts with stabilized Ni-La bimetals nanoparticles for dry reforming of methane

Dry reforming of methane (DRM) can simultaneously convert two critical greenhouse gases CH4 and CO_(2) into high-value syngas. However, the catalyst deactivation caused by sintering and carbon deposition of Ni-based catalysts at high temperature is a significant problem to be solved for DRM industrialization. Herein, we represent a hierarchical Ni-La@S-1 catalyst for DRM reaction, showing high anti-sintering/coke capacity to improve DRM stability. The La and Ni nitrates were first grinded into the pores of SBA-15 followed by N2-treatment;the sample was then recrystallized by a unique template assisted-uniformly dispersed strategy to obtain the hierarchical Ni-La@S-1 catalyst. This strategy achieves uniform encapsulation of stabilized Ni-La bimetallic nanoparticles in S-1 with high loading, exhibiting high DRM activity and stability at 700 °C and 36,000 mL·g^(−1)·h^(−1). Moreover, La addition promoted CO_(2) to form bidentate carbonate, a critical intermediate in DRM, which greatly ameliorated carbon deposition in Ni catalysts. This work offers promising clue for tailoring the industrial DRM catalysts.

High-performance aluminum-polyaniline battery based on the interaction between aluminum ion and-NH groups

Aluminum-ion batteries(AIBs)are a type of promising energy storage device due to their high capacity,high charge transfer efficiency,low cost,and high safety.However,the most investigated graphitic and metal dichalcogenide cathodes normally possess only a moderate capacity and a relatively low cycling stability,respectively,which limit the further development of high-performance AIBs.Here,based on the results of first principles calculations,we developed a polyaniline/graphene oxide composite that exhibited outstanding performances as a cathode material in AIBs(delivering 180 mA h g^−1 after 4000 cycles),considering both the discharge capacity and the cycling performance.Ex-situ characterizations verified that the charge storage mechanism of polyaniline depended on the moderate interactions between−NH in the polyaniline chain and the electrolyte anions,such as AlCl4^−.These findings lay the foundation of the development of high-performance AIBs based on conducting polymers.

Ru-based catalysts for efficient CO_(2) methanation:Synergistic catalysis between oxygen vacancies and basic sites

The fundamental insights of the reaction mechanism,especially the synergistic effect between oxygen vacancies and basic sites,are highly promising yet challenging for Ru-based catalysts during carbon dioxide(CO_(2))methanation.Herein,a series of Rubased catalysts were employed to study the mechanism of CO_(2) methanation.It is found that Ru/CeO_(2) catalyst exhibits a much higher CO_(2) conversion(86%)and CH4 selectivity(100%),as well as excellent stability of 30 h due to the existence of abundant oxygen vacancies and weak basic sites.Additionally,the in-situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS)and density functional theory(DFT)calculations reveal that the formate formation step dominated the hydrogenation route on Ru/CeO_(2) catalyst,and the b-HCOO^(*)could be the key intermediate due to b-HCOO^(*)is more easily hydrogenated to methane than m-HCOO^(*).The systematic study marks the significance of precise tailoring of the synergistic relationship between oxygen vacancies and basic sites for achieving the desired performance in CO_(2) methanation.

Realizing the Long Lifespan of Molybdenum Trioxide in Aqueous Aluminum Ion Batteries Through Potential Regulation

MoO_(3) is one of the most promising anode materials for aqueous aluminum batteries due to its high theoretical capacity and suitable aluminum insertion/de-insertion potential.However,the inferior cycling stability limits its further application,and the failure mechanism is still unclear.In this article,we provide a straightforward potential regulation technique to manage phase evolution during the charge/discharge process,which ultimately results in a markedly enhanced MoO_(3) electrode cycling stability.The failure mechanism study reveals that the excessive oxidation of the electrode during charge/discharge generates the H_(0.34)MoO_(3) phase,which has high solubility and is the primary cause of MoO_(3) deactivation.Although the dissolved Mo species will be deposited onto the electrode sheet again,the deposition is not electrochemically active and cannot contribute to the capacitance.Controlling the cutoff potential prevented the production of H_(0.34)MoO_(3),resulting in excellent cycling performance(80.1% capacity retention after 4000 cycles).The as-assembled α-MoO_(3)//MnO_(2) full battery exhibits high discharge plateaus(1.4 and 0.9 V),large specific capacity(200 mAhg^(-1) at 2 Ag^(-1)),and ultra-high coulombic efficiency(99%).The research presented here may contribute to the development of highly stable electrode materials for aqueous batteries.

Construction of Frame-Structured Flexible MXene Film Electrode to Achieve High Areal Capacitance Micro-Supercapacitor

Two-dimensional MXene-based film materials as flexible electrodes have been widely studied in wearable microsupercapacitors(MSCs).However,the existence of strong van derWaals interactions leads to serious self-stacking ofMXene layers,resulting in poor ionic dynamics and loss of active sites,which causes MXene film electrodes to exhibit low capacitance and poor rate performance in practical studies.To solve this,a frame-structured hybrid film(labeled as CN-MX hybrid film)is constructed by introducing intercalating agents(nanometer g-C_(3)N_(4))into MXene layers.In this unique hybrid film,the g-C_(3)N_(4)nanoparticles rationally occupy the interspace between MXene layers so as to alleviate layer stacking,thus effectively expanding the electrochemically active surface and promoting proton transfer.Synergistic pseudocapacitance inducted by g-C_(3)N_(4)surface groups,consequently,the CN-MX hybrid film electrode achieves an enhanced capacitive capability.In the three-electrode system,this frame-structured film electrode exhibits an ultra-high areal capacitance of 1932.8 mF cm^(−2).The assembled symmetry flexible MSC device based on CN-MX hybrid film can achieve an energy density of 2.28μWh cm^(−2)at 0.075 mW cm^(−2),as well as a superior cyclic stability with 90.4%retention after 700 cycles in alternating 90o bending and releasing states,revealing its potential in practical applications.

Ultrasmall NiFe layered double hydroxide strongly coupled on atomically dispersed FeCo-NC nanoflowers as efficient bifunctional catalyst for rechargeable Zn-air battery

An atomically dispersed FeCo-NC material with the 3D flower-like morphology was used as a unique substrate for the controllable deposition of ultrasmall NiFe layered double hydroxide nanodots(termed as NiFe-NDs)to simultaneously promote the sluggish kinetics of oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).The size-limiting growth of NiFe-NDs(~4.0 nm in diameter)was realized via the confinement of the 3D flower-like mesoporous structure and the rich N/O functionality of FeCo-NC.Benefiting from the distinctive structure with the simultaneously maximum exposure of both OER and ORR active sites,the NiFe-ND/FeCo-NC composite showed an ORR halfwave potential of 0.85 V and an OER potential of 1.66 V in0.1 mol L-1KOH at 10.0 mA cm-2.In-situ Raman analysis suggested the activity of OER was derived from the Ni sites on NiFe-ND/FeCo-NC.Moreover,the NiFe-ND/FeCo-NC-assembled Zn-air battery(ZAB)exhibited a very small discharge-charge voltage gap of 0.87 V at 20 mA cm-2and robust cycling stability.Furthermore,the NiFe-ND/FeCo-NC composite was also applicable for fabricating all-solid-state ZAB to power wearable electronics with superior cycling stability under deformation.Our work could enlighten a new applicable branch of atomically dispersed metal-nitrogen-carbon materials as unique substrates for fabricating multifunctional electrocatalysts.

Hierarchical peony-like FeCo-NC with conductive network and highly active sites as efficient electrocatalyst for rechargeable Zn-air battery

Carbon materials featuring hierarchical pores and atomically dispersed metal sites are promising catalysts for energy storage and conversion applications.Herein,we developed a facile strategy to construct functional carbon materials with a fluffy peony-like structure and dense binary FeCo-Nx active sites(termed as f-FeCo-CNT).By regulating the metal content in precursors,a three-dimensional(3D)interconnected conductive carbon nanotubes network was in-situ formed throughout the atomically dispersed FeCo-NC matrix during pyrolysis.Taking advantage of rich pore hierarchy and co-existence of highly active FeCo-Nx sites and beneficial FeCo alloy nanoparticles,the f-FeCo-CNT material exhibited excellent bifunctional performance towards oxygen reduction reaction/oxygen evolution reactions(ORR/OER)with respect to the atomically dispersed FeCo-NC(SA-f-FeCo-NC)and commercial Pt/C+Ru02 mixture,surpassing the SA-f-FeCo-NC with a 20 mV higher ORR half-wave potential and a 100 mV lower OER overpotential(at 10.0 mA/cm^2).Remarkably,the f-FeCo-CNT-assembled Zn-air battery(ZAB)possessed a maximum specific power of 195.8 mW/cm^2,excellent rate capability,and very good cycling stability at large current density of 20.0 mA/cm^2.This work provides a facile and feasible synthetic strategy of constructing low-cost cathode materials with excellent comprehensive ZAB performance.

One-pot synthesis of the highly efficient bifunctional Ni-SAPO-11 catalyst

Hydro isomerization of linear alkanes to branched isomers is an important petrochemical process for production of gasoline with high octane number.Non-noble metal bifunctional catalysts used in this process always suffer from low metal dispersion and poor metal-acid synergy.Herein,a facile one-pot synthesis method was used to simultaneously regulate metal particle sizes and acidity of the Ni-SAPO-11 hydroisomerization catalyst.The physicochemical properties are investigated using XANES,EXAFS,TEM/STEM,FT-IR,XPS,UV-vis and NH_3-TPD.Apart from the highly dispersed nickel nanoparticles with an average diameter of 8 nm,the framework Ni~(2+)ions are generated via substituting framework Al~(3+)ions of the SAPO-11.The formed NiP-OH structures have lower deprotonation energy(DPE)than the SiAl-OH ones,contributing more and stronger acid sites to the Ni-SAPO-11 catalyst.The great metal-acid synergy including high metal to acid sites ratio(n_(Ni)/n_A)and close intimacy is obtained for the Ni-SAPO-11 catalyst.The Ni-SAPO-11 catalyst outperforms the counterpart prepared by the impregnation method and exhibits comparable activity and isomers selectivity to the Pt/SAPO-11 catalyst in the n-hexane hydroisomerization.

Preparation of Cu/ZrO2 catalysts for methanol synthesis from CO2/H2

Cu/ZrO2 catalysts for methanol synthesis from CO2/H2 were respectively prepared by deposition coprecipitation （DP） and solid state reaction （SR） methods. There is an intimate interaction between copper and zirconia, which strongly affects the reduction property and catalytic performance of the catalysts. The stronger the interaction, the lower the reduction temperature and the better the performance of the catalysts. Surface area, pore structure and crystal structure of the catalysts are mainly controlled by preparation methods and alkalinity of synthesis system. The conversion of CO2 and selectivity of methanol are higher for DP catalysts than for SP catalysts.

Ag@Au core/shell triangular nanoplates with dual enzyme-like properties for the colorimetric sensing of glucose

Due to the serious harm of diabetes to human health,development of sensitive assays for glucose level is of high significance for early prevention and treatment of diabetes.Currently,most conventional enzyme-based glucose sensors suffer from high cost and low stability due to the inherent defects of natural enzymes.Herein,we develop a pure nanozyme-based glucose detection method using Ag@Au core/shell triangular nanoplates(TNPs),which combines glucose oxidase(GOD)-and horseradish peroxidase(HRP)-like activities of the Au shell and inherent plasmonic properties of Ag TNPs.The sensing mechanism is based on the fact that the Au shell possessed GOD-like activity,enabling the oxidation of glucose to produce H2O2,which can further etch the silver core,leading to the decrease of absorbance at 800 nm and the color change from blue to colorless.Compared with the previous nanozymes-based glucose sensors,our method avoids the use of enzymes and organic chromogenic agent.Moreover,the stability of the Ag@Au core/shell TNPs is much better than that of Ag TNPs due to the protection by the coating of the Au shell.This method was successfully applied to the detection of urine samples from patients with diabetes,indicating its practical applicability for real sample analysis.

Epitaxial growth of hyperbranched Cu/Cu2O/CuO coreshell nanowire heterostructures for lithium-ion batteries

The careful design of nano-architectures and smart hybridization of expected active materials can lead to more advanced properties. Here we have engineered a novel hierarchical branching Cu/Cu2O/CuO heteronanostructure by combining a facile hydrothermal method and subsequent controlled oxidation process. The fine structure and epitaxial relationship between the branches and backbone are investigated by high-resolution transmission electron microscopy. Moreover, the evolution of the branch growth has also been observed during the gradual oxidation of the Cu nanowire surface. The experimental results suggest that the surface oxidation needs to be performed via a two-step exposure process to varying humidity in order to achieve optimized formation of a core-shell structured branching architecture. Finally, a proof-of-concept of the function of such a hierarchical framework as the anode material in lithium-ion batteries is demonstrated. The branching core-shell heterostructure improves battery performance by several means： （i） The epitaxially grown branches provide a high surface area for enhanced electrolyte accessibility and high resistance to volume change induced by Li^＋ intercalation/extraction; （ii） the core-shell structure with its well-defined heterojunction increases the contact area which facilitates effective charge transport during lithiation; （iii） the copper core acts as a current collector as well as providing structural reinforcement.

Narrow-bandgap Nb_2O_5 nanowires with enclosed pores as high-performance photocatalyst

Porous niobium oxide nanowires synthesized via a solvothermal method exhibited decreased bandgap,en- hanced light absorption and reduced charge-recombination rate.The porous Nb2O5 nanowires showed increased performance for the photocatalytic H2 evolution and photo- degradation of rhodamine B,as compared to their solid counterparts,which could be ascribed to the peculiar porous nanostructure.

Single-atom Zn for boosting supercapacitor performance

Single-atom metal-incorporated carbon nanomaterials(CMs)have shown great potential towards broad catalytic applications.In this work,we show that N-doped porous CMs embedded with redox-able Zn atoms exhibit superior capacitive performance.High Zn(~2.72 at.%)/N(~12.51 at.%)doping were realized by incorporating Zn2+and benzamide into the condensation and carbonization of formamide and subsequent annealing at 900℃.The Zn and N species are mutually benefited during the formation of ZnN4 motif.The as-obtained Zn1NC material affords a very large capacitance of 621 F·g^(−1)(at 0.1 A·g^(−1)),superior rate capability(~65%retention at 100 A·g^(−1)),and excellent cycling stability(0.00044%per cycle at 10 A·g^(−1)).These merits are attributed to the high Zn/N loading,atomic Zn-boosted pseudocapacitive behavior,large specific surface area(~1,085 m^(2)·g^(−1)),and rich pore hierarchy,thus ensuring both large pseudo-capacitance(e.g.,~37.9%at 10 mV·s^(−1))and double-layer capacitance.Besides of establishing a new type of high Zn/N-loading carbon materials,our work uncovers the capacitive roles of atomically dispersed metals in CMs.

Dual carbon Li-ion capacitor with high energy density and ultralong cycling life at a wide voltage window

Using the same materials for the cathode and anode in energy storage devices could greatly simplify the technological process and reduce the device cost significantly.In this paper,we assemble a dual carbon-based Li-ion capacitor with the active materials derived entirely from a single precursor,petroleum coke.For the anode,petroleum cokederived carbon(PCC)is prepared by simple ball milling and carbonization,having a massive tap density(1.80 g cm^(-3))and high electrical conductivity(11.5 S cm^(-1)).For the cathode,the raw petroleum coke is activated by KOH(petroleum cokeactivated carbon(PC-AC)sample)to achieve a well-developed pore structure to meet a rapid capacitive behavior.As a result,in addition to the robust structural stability of both the anode and cathode,the assembled dual carbon Li-ion capacitor shows a high energy density(231 W h kg^(-1)/206 W h L^(-1))and ultralong cycling life(up to 3000/10,000 cycles)at a wide voltage window.The excellent electrochemical response and simple production process make the PCC materials have great potential for practical application.

Transesterification of soybean oil to biodiesel over kalsilite catalyst

The transesterification reaction of soybean oil with methanol over kalsilite-based heterogeneous catalysts was investigated.The kalsilite was synthesized from potassium silicate,potassium hydroxide,and aluminum nitrate aqueous solutions by controlling the pH value at 13.After calcination in air at 1200°C,a very porous kalsilite(KAlSiO4)was obtained with surface pores ranging from 0.2 to 1.0µm.However,this kalsilite had relatively low catalytic activity for the transesterification reaction.A biodiesel yield of 54.4%and a kinematic viscosity of 7.06 cSt were obtained at a high reaction temperature of 180°C in a batch reactor.The catalytic activity of kalsilite was significantly enhanced by introducing a small amount of lithium nitrate in the impregnation method.A biodiesel yield of 100%and a kinematic viscosity of 3.84 cSt were achieved at a temperature of only 120°C over this lithium modified catalyst(2.3 wt-%Li).The test of this lithium modified catalyst in pellet form in a laboratory-scalefixed-bed reactor showed that it maintained a stable catalytic performance with a biodiesel yield of 100%over thefirst 90 min.

Effect of potassium carbonate on catalytic synthesis of calcium carbide at moderate temperature

Calcium carbide was successfully synthesized by carbothermal reduction of lime with coke at 1973 K for 1.5 h.The effect of potassium carbonate as additive on the composition and morphology of the product was investi-gated using X-ray diffraction and scanning electron microscope.Addition of potassium carbonate increased the yield of calcium carbide.The sample in the presence of potassium carbonate generated acetylene gas of 168.3 L/kg,which was 10%higher than that in the absence of potassium carbonate.This result confirmed the catalytic effect of potassium carbonate on the synthesis of calcium carbide.A possible mechanism of the above effects was that the additive,which was melted at the reduction temperature,dissolved CaO and so promoted the contact between CaO and carbon,which was essential for the solid-solid reaction to form calcium carbide.

Magnetic rod-based metal-organic framework metal composite as multifunctional nanostirrer with adsorptive,peroxidase-like and catalytic properties

Although magnetic stirring is frequently used to enhance the kinetics for adsorption,chemical and biochemical reactions,the introduction of stirrers inevitably leads to the adsorption of analytes and thus interferes with the efficiency of the chemical process or reaction.In this work,magnetic Fe_(3) O_(4) nanorods with tunable length-to-diameter ratio were synthesized via a hydrothermal method and used as templates for the in-situ depositing of MIL-100(Fe) and gold nanoparticles.Such nanorod-based material can not only function as an adsorbent,nanozyme,and a heterogeneous catalyst for corresponding applications but also serve as a magnetic nanostirrer to enhance kinetics.As a proof-of-concept,the capture of bacteria pathogen,mimic-peroxidase-based colorimetric detection of hydrogen peroxide,and the catalytic reduction of selected organic pollutants were conducted using the as-synthesized Fe_(3) O_(4)@MIL-100(Fe)-Au nanostirrer with and without magnetic field.The results show that the rates of bacteria capture,mimetic enzyme reaction and catalysis were tremendously expedited.We believe this magnetic field-assisted approach holds great promise for future applications,because,not only does it eliminate the use of external magnetic stirrers and thereby decrease the risk of foreign pollution but also,is adaptable for nanoscale reaction systems where conventional stirring is not applicable due to size limitations.