High-temperature Pyrolysis Method Research Articles

Biomass-Derived-Carbon-Supported Spinel Cobalt Molybdate as High-Efficiency Electrocatalyst for Oxygen Evolution Reaction.

Ananas comosus leaves were converted to a porous graphitized carbon (GPLC) material via a high-temperature pyrolysis method by employing iron salt as a catalyst. A cobalt molybdate (CoMoO4)-and-GPLC composite (CoMoO4/GPLC) was then prepared by engineering CoMoO4 nanorods in situ, grown on GPLC. N2 adsorption-desorption isothermal curves and a pore size distribution curve verify that the proposed composite possesses a porous structure and a large specific surface area, which are favorable for charge and reactant transport and the rapid escape of O2 bubbles. Consequently, the as-synthesized CoMoO4/GPLC shows low overpotentials of 289 mV and 399 mV to afford the current densities of 10 mA cm-2 and 100 mA cm-2 towards the oxygen evolution reaction (OER), which is superior to many CoMoO4-based catalysts in previous studies. In addition, the decrease in current density is particularly small, with a reduction rate of 3.2% after a continuous OER procedure for 30 h, indicating its good stability. The excellent performance of the CoMoO4/GPLC composite proves that the GPLC carrier can obviously impel the catalytic activity of CoMoO4 by improving electrical conductivity, enhancing mass transport and exposing more active sites of the composite. This work provides an effective strategy for the efficient conversion of waste ananas comosus leaves to a biomass-derived-carbon-supported Co-Mo-based OER electrocatalyst with good performance, which may represent a potential approach to the development of new catalysts for OER, as well as the treatment of waste biomass.

Silicon-air batteries enabled by in-situ FeMn alloy-catalyzed nitrogen-doped carbon nanotube arrays as efficient air electrodes catalysts

Silicon-air batteries (SABs) have become promising candidates for energy conversion and storage devices due to their high theoretical energy density, cost-effectiveness, and inherent safety. However, the slow kinetics of the 4e− transfer in the oxygen reduction reaction (ORR) at the cathode during discharge, coupled with severe polarization, reduces the battery’s capacity and hinders the development of silicon-air batteries. The cathodes of currently developed SABs primarily rely on commercial Pt/C and MnO2, with limited research on low-cost, efficient, and stable air cathodes for SABs. To address this issue, we synthesized nitrogen-doped carbon nanotubes containing FeMn alloy particles (FeMn@NCNTs) as cathode ORR catalysts using a simple high-temperature pyrolysis method combined with chemical vapor deposition. In an alkaline medium, the catalyst’s half-wave potential (E1/2) reached 0.83 V. Moreover, the FeMn@NCNTs air cathode exhibited excellent compatibility with the silicon anode, and the constructed aqueous silicon-air battery demonstrated a high specific capacity (165 Ah kg−1) and power density (3.69 mW cm−2). Additionally, the quasi-solid-state SABs constructed with FeMn@NCNTs showed stable operation over a wide temperature range, providing a new solution for the development of low-cost, efficient silicon-air batteries suitable for a wide range of applications.

Pt nanoparticles loaded on three-dimensional porous carbon as electrocatalysts for hydrogen evolution reaction

The electrochemical catalytic hydrogen evolution reaction (HER) holds significant potential for the sustainable production of environmentally friendly hydrogen energy. Currently, the precious metal Pt is widely acknowledged as the most superior electrocatalyst. However, its limited availability and exorbitant cost impede its extensive application. In this study, low Pt-loaded three-dimensional (3D) porous carbon composites were successfully synthesized as catalysts using a template-free method and a high-temperature pyrolysis method. By evaluating the HER performance of different Pt concentrations of the catalysts Pt/C-X (X=0, 0.05, 0.1, 0.2, 0.4, 0.7 mmol) in acid solution, it was observed that the overpotential of Pt/C-0.2 reached as low as 17 mV with a significantly low Tafel slope value of 48 mV cm−2. Meanwhile, the Bilayer capacitance (Cdl) reached an impressively high value of 247.5 mF cm−2. Consequently, this also provides a promising way to enhance the catalytic performance of the loaded catalysts.

Ultrahigh nitrogen-doped carbon derived from g-C3N4 assisted by citric acid for superior potassium-ion storage

Nitrogen-doped carbon is regarded as a promising anode for potassium ion batteries (PIBs) because nitrogen atoms can regulate the structures of carbon and generate abundant active sites. How to improve the nitrogen content in carbon through simple and effective methods remains to be further addressed. In this paper, a carbon material (60NC) with ultrahigh nitrogen content (16 %) was prepared from graphite phase carbon nitride (g-C3N4) by a convenient freeze-drying and high-temperature pyrolysis method, assisted by citric acid. When used as an anode for PIBs, 60NC exhibited a superior reversible capacity of 318.1 mAh g−1 after 200 cycles at 0.1 A g−1. Even at the high current density of 1A g−1, 60NC maintained a specific capacity of 261.8 mAh g−1 after 1000 cycles. The excellent electrochemical performance of 60NC mainly stems from its abundant K+ storage active sites caused by nitrogen doping, large layer spacing, and hierarchical porous structure.

Synthesis of activated carbon from waste polyester fabric activated by ZnCl2 and its adsorption for organic dyes

In order to achieve the resource utilization of waste polyester (WPT), the WPT based activated carbon (WPT-AC) was prepared by ZnCl2 activation high-temperature pyrolysis method. The phase morphology, characteristic groups, pore structure of specific surface area and microstructure were characterized by TGA, XRD, FTIR, BET and SEM. The optimum preparation process of WPT-AC was determined by L9(34) orthogonal experiment, and the adsorption performance of WPT-AC for methylene blue (MB) was evaluated. WPT-AC showed a high specific surface area of 1037.62 m2/g, with rich pore structure, which provided the possibility for efficient adsorption. The pretreatment of ZnCl2 plays a key role in the formation of WPT-AC pore structure, and the abundant pore structure is conducive to improving the adsorption of pollutants. WPT-AC showed excellent performance in the field of organic dye adsorption, and the highest removal rate of MB reached 97.34%. The adsorption was mainly related to electrostatic attraction, hydrogen bonding and π–π conjugation. The analysis of adsorption kinetics and thermodynamics is conducive to a better understanding of the adsorption process.

P507-modified magnetic porous carbon derived from metal-organic frameworks for efficient separation of zirconium(IV) and hafnium(IV)

Extractant-based solid phase extraction exhibit practical application potential for efficient separation of Zr(IV) and Hf(IV), where the key is to regulate the host–guest interaction between the guest extraction agents and the host matrices to obtain high performance. However, the current research on the host matrices of extraction agents is insufficient. Leveraging the tunability of metal–organic frameworks (MOFs), we successfully prepared a magnetic MOF-derived porous carbon (C(Zn/Co-ZIF)) with a high specific surface area and Co-Nx active sites as an excellent matrix. This was achieved by deliberately controlling the pore volume and microenvironment through a mixed precursor strategy and high-temperature pyrolysis method. Furthermore, as an excellent extractant for the separation of Zr(IV) and Hf(IV) in solvent extraction, 2-ethylhexyl phosphonic acid mono-(2-ethylhexyl) ester (P507) was carefully selected to modify C(Zn/Co-ZIF) to obtain C(Zn/Co-ZIF)@P507 by impregnation. Impressively, the maximum adsorption capacities of C(Zn/Co-ZIF)@P507 for Zr(IV) and Hf(IV) were up to be 0.58 and 0.39 mmol/g, respectively, while exhibiting excellent separation coefficient. Further mechanism studies indicated that the combination of high specific surface area and abundant Co-Nx active sites of C(Zn/Co-ZIF) leaded to strong interaction with P507, resulting in the excellent adsorption and separation performance of Zr(IV) and Hf(IV) based on the coordination between phosphinic groups of P507 and Zr(IV)/Hf(IV).

Mn-NSC co-doped modified biochar/permonosulfate system for degradation of ciprofloxacin in wastewater

Mn-Nitrogen-sulfur co-doped modified biochar (Mn-NSCX) is prepared by high-temperature pyrolysis and hydrothermal method, and its properties are analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). A metal-non-technical co-doping system was constructed and first used for PMS activation towards ciprofloxacin degradation. The results show that doping of Mn, N and S significantly improve the catalytic performance of activated PMS to degrade CIP, among which Mn-NSC2 exhibit the best catalytic performance, when the dosage of MN-NSC2 is 0.4 g·L−1, the concentration of PMS is 0.4 mmol·L−1, and the concentration of CIP is 20 mg·L−1. After 60 min, more than 99% of CIP can be removed, among which the CIP removal rate of BC/PMS is 43.6%, and the CIP removal rate of NSC5/PMS is 50.3%. The removal effect of CIP is greatly improved after the incorporation of manganese, attributing to the oxidation reaction between the PMS and manganese dioxide. The results of electron paramagnetic resonance (EPR) indicate that both free radicals (·SO4-,·OH) and non-free radicals (1O2) play important roles in the degradation of CIP, and 1O2 plays a foremost role in the degradation of CIP. Doping of Mn, N and S accelerate the electron transfer rate and improve the catalytic activity of the material. In this paper, the loading of metal oxides can increase the corresponding catalytic sites and promote electron transfer, thus promoting the ability of activated PMS to degrade organic pollutants. The metal modification not only improves the oxygen-containing groups of the material, but also promotes the activation of persulfate by metal oxidation on the surface of the material. A novel design and preparation strategy for catalyst is proposed to simultaneously achieve stable Mn-Nitrogen-sulfur co-doped modified biochar and improve the catalytic performance of biochar by adding Mn, S, and N.

Si@C anode with excellent electrochemical performance for lithium-ion batteries: Microcapsules composed of N-doped carbon shell and diffusely distributed nano-silicon inside

As a promising candidate for the next generation of new anode materials, the modification and optimization of silica-based anode materials are significant. Using chitosan (CS) as the carbonaceous precursor, the N-containing Si@C microcapsules were prepared by emulsification cross-linking combined with high-temperature pyrolysis method. The microcapsule structure offers additional space for nano-Si and effectively enhances the electrochemical properties of the anode. Moreover, optimizing the CS:Si ratio is advantageous in achieving a synergistic effect between silicon and carbon. When CS:Si = 4:1, the first specific capacity was 762.78 mAh/g and the retention rate was 69.27 % after 100 cycles. To further enhance the material properties, urea was added to a ratio of CS:Si = 4:1 as an N supplement for elemental doping modification. The specific capacity of the anode had a positive correlation with N content within a certain range. As the N content increases, the pyridine-N content and density of C vacancies also increase, which improves the storage form and diffusion path of Li+. When 0.75 g urea was added, the first reversible specific capacity reached 1108.88 mAh/g and the retention rate was 92.41 % after 100 cycles. This work offers environmentally friendly and safe methods, as well as a new modification concept for N-doped microsphere-encapsulated silicon-carbon composites.

Facile synthesis of excellent Fe3O4@starch-derived carbon Photo-Fenton catalyst for tetracycline degradation: Rapid Fe3+/Fe2+ circulation under visible light condition

Photoinduction is widely used to accelerate the Fe3+/Fe2+ circulation in Fe3+/H2O2 Fenton oxidation, however, the remained challenges in developing a facile, economical, and efficient synthetic methodology for the preparation of high-performance Fe-based Photo-Fenton catalyst and inevitably forming iron sludge limit its applications. Herein, starch-derived carbon (SC) encapsulated Fe3O4 (Fe3O4@SC) magnetic nanocomposites are synthesized by mechanical activation treatment combined with high-temperature pyrolysis method using cassava starch as the carbon source. The photoelectrochemical properties of Fe3O4@SC are regulated by COFe bonds and oxygen vacancies in Fe3O4@SC, as well as graphitization of SC, which effectively accelerate the Fe3+/Fe2+ circulation in Fe3O4@SC + H2O2 system under visible light, thus Fe3O4@SC shows excellent catalytic performance and superior stability for the degradation of tetracycline hydrochloride, and the initiation rate constant is 2.4 times higher than that in dark. Moreover, quenching experiments and electron spin resonance results confirm that OH, O2−, and h+ (OH plays a critical role) are generated in the catalytic system of Fe3O4@SC + H2O2 + visible light. This work provides new insights into a green and facile approach for the synthesis of Photo-Fenton catalysts, providing new avenue for the acceleration of Fe3+/Fe2+ cycle under visible light-driven Fenton process.

Conformal BN coating to enhance the electrical insulation and thermal conductivity of spherical graphite fillers for electronic encapsulation field

Herein, we provided a structural design strategy of constructing boron nitride (BN) conformal coating on the surface of the spherical graphite (SG) particles via precursors deposition and high-temperature pyrolysis method to achieve improved electrical insulation. The dissolved and reprecipitated BN precursors were uniformly deposited on the surface of polydopamine-modified SG through strong adhesion and hydrogen bonding of polydopamine. Then, the homogeneous and dense BN ceramic coating was formed on the surface of SG via slow pyrolysis at high temperature. The complete encapsulation of BN coating prevents the SG particles directly contacting with each other in the silicon rubber (SR) matrix to retain electrical insulation of SR composites. Furthermore, the BN coating flattens the uneven surface of SG so that the fillers are better infiltrated by the SR matrix. The small specific surface area of SG@BN filler particles is beneficial to significantly reduce the generation of the filler/matrix interfaces and weaken phonons scattering, thus decreasing the thermal boundary resistance. As a result, the thermal conductivity of prepared SG@BN/SR composites is up to 3.65 W m−1 K−1, which is 20.2-fold of that of pure SR with 0.18 W m−1 K−1. And the SG@BN/SR composites exhibit a satisfactory breakdown voltage of 5.6 kV mm−1, which is much higher than 1.1 kV mm−1 for the original SG/SR composites. This strategy is worth using for reference to extend the application of graphite-type fillers in the electronic encapsulation field.

A bio-waste derived sustainable heterogenous catalyst for Biginelli reaction

This study is targeted at agricultural waste-derived heterogeneous catalysts, which have been effectively employed for Biginelli reaction. The application of cotton waste (Gossypium) derived lignin as a heterogeneous catalyst for C–C bond formation via one pot multicomponent Biginelli reaction. Here we hypothesize that the preparation of bio-waste derived catalyst by high temperature pyrolysis method under anaerobic conditions. The bio-waste derived heterogeneous catalyst (BDC) was well characterized by using different analytical techniques such as BET, SEM, TEM, XRD, DSC, TGA, ICP. The acidity of the catalyst was determined by a Hammett indicator test and titration method. An excellent yield of 6-methyl-2-oxo/thio-4-phenyl substituted-1,2,3,4-tetrahydropyrimidine-5-ethyl carboxylate derivatives was obtained in shorter reaction time (>80% yield in 15–30 min). The catalyst used in these studies has the advantage of being a waste material. Consequently, it is a low-cost, easily prepared, recyclable and environmentally benign. In addition, the use of a biogenic renewable catalyst, its atom economy, and room temperature and solvent-free reaction conditions and the avoidance of column chromatography make the protocol highly significant from green and sustainable chemistry perspectives. The synthesized compounds were characterized by modern analytical techniques like NMR, MS, FT-IR, CHNS analysis. The experimental parameters like % mole of catalyst, mole ratio, temperature and time for reaction completion were also optimized to achieve maximum yield and purity. The surface interaction between BDC and reactant was also studied.

Study of charge transfer contribution in Surface-Enhanced Raman scattering (SERS) based on indium oxide nanoparticle substrates

Surface-enhanced Raman scattering (SERS) has outstanding merits in biochemical molecular analysis, and the development of new SERS substrates is the focus of research. Herein, In2O3 nanoparticles (NPs) were synthesized by a high temperature pyrolysis method with cubic phase and small particle size at 10 nm. The structures and properties of In2O3 NPs were characterized by X–ray powder diffraction (XRD), transmission electron microscope (TEM) and other characterization methods. Additionally, the SERS spectra of In2O3-MBA with the enhancement factor (EF) up to 1.22 × 104 is discussed. The results demonstrate that there is a charge transfer (CT) effect revealed between the adsorbed molecules of 4-mercaptobenzoic acid (4-MBA) and the substrates of In2O3 NPs, and it could be excited by long wavelength energy. Based on the In2O3 NPs, the study is beneficial to develop more potential semiconductor SERS substrates.

Adsorption-Reduction of Cr(VI) with Magnetic Fe-C-N Composites

In this study, the iron-based carbon composite (hereafter FCN-x, x = 0, 400, 500, and 600 calcination) was synthesized by a simple high-temperature pyrolysis method using iron-containing sludge coagulant generated from wastewater treatment settling ponds in chemical plants. The FCN-x was used for the adsorptive reduction of aqueous phase Cr(VI) effectively. The FCN-x was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier infrared spectrometer (FT-IR), X-ray photoelectron spectrometer (XPS), and Brunauer-Emmett-Teller theory (BET). FCN-x adsorption of Cr(VI) was examined in batch experiments using CrO42− as a function of physicochemical parameters. The chemical kinetics of Cr(VI) adsorption by FCN-500 were modeled by 1st and 2nd order empirical pseudo kinetics. Based on these experiments, FCN-500 has been selected for further studies on Cr(VI) adsorptive reduction. The maximum Cr(VI) adsorption by FCN-500 was 52.63 mg/g showing the highest removal efficiency. The Cr(VI) adsorption by the FCN-500 was quantified by the Langmuir isotherm. XPS result confirmed the reduction of Cr(VI) to Cr(III) by the FCN-500. The iron-based carbon composites have high reusability and application potential in water treatment. The electroplating wastewater with 117 mg/L Cr(VI) was treated with FCN-500, and 99.93% Cr(VI) was removed within 120 min, which is lower than the national chromium emission standard of the People’s Republic of China. This work illustrates the value-added role of sludge generated from dye chemical plants to ensure environmental sustainability.

Synthesis of nano-tube CoNi/N–C complex and its catalytic properties for highly efficient oxygen reduction

Electrochemical energy storage systems such as fuel cells and metal air cells can be used as clean energy. In these systems, an essential reaction on the cathode is the oxygen reduction reaction (ORR). As ORR catalyst, non noble metal based catalyst is an important substitute for commercial Pt/C catalyst due to its rich reserves, low cost, good stability and high catalytic activity. Herein, CoNi alloy supported on nitrogen doped carbon, CoNi/N–C nanotubes, prepared by hydrothermal method and high-temperature pyrolysis method, shows excellent ORR catalytic activity and stability in 0.1 M KOH solution. In particular, the obtained CoNi/N-C-800 demonstrates the highest ORR activity of the prepared samples, with a half wave potential of 0.81V, which was equivalent to the commercially available Pt/C (0.82V). At the same time, it exhibits approximate 4e- pathway with a comparable electron transfer number to the commercial Pt/C, and is much higher tolerant in methanol than the latter. Co and Ni alloying can induce the internal electron interaction of the catalyst, thus exposing more active sites. Furthermore, nano-tube CoNi exhibits appropriate size and hollow geometry, and its large surface area and strong conductivity improve its catalytic activity. The results may possibly provide a new impetus to the rational design of non noble metal based nanocomposite catalysts. Moreover, it is also of great significance to improve the performance of electrocatalysis and energy storage applications.

High-performance two-photon absorption optical limiter and stabilizer based on phase-pure thick-shell CdSe/CdS core/shell quantum dots

To achieve high-sensitivity two-photon absorption (2PA) optical limiters and stabilizers, two-photon active materials need to have large 2PA cross-sections. Phase-pure wurtzite (WZ) CdSe/CdS core/shell quantum dots (QDs) with a shell thickness of 11 CdS monolayers were prepared by a high-temperature pyrolysis method, which possess a large volume and nearly defect-free core/shell interfaces. The 2PA cross-section of QDs is measured to be as large as 1.5 × 105 GM by the nonlinear transmittance method. Due to the large 2PA cross-section of phase-pure thick-shell WZ CdSe/CdS core/shell QDs, we successfully explored their application in the field of optical limiting and stabilization. Finally, we successfully fabricated a high-sensitivity optical stabilizer made of a polymer (polymethylmethacrylate) matrix comprising phase-pure thick-shell WZ CdSe/CdS core/shell QDs, which can reduce the amplitude fluctuation by ∼67%. In addition, the device reduces the input energy by ∼40%, indicating that the device can also be applied as an optical limiter. This work promotes the application of optical limiters and stabilizers based on QDs in practical work to a certain extent.

Evaluation of modified bitumen properties using waste plastic pyrolysis wax as warm mix additives

The existing disposal methods of waste plastics are mainly landfill and incineration, and they will migrate to the surrounding ecosystems and bio-magnify in plants and animals that endanger the human food chain. To reduce environmental pollution and realize waste reuse, the waste plastics were recycled to produce the pyrolysis wax (PW) as warm mix additives of bitumen by using the high-temperature pyrolysis method in this study. The PW was produced at different pyrolysis temperatures (T) and pressures (P), and then bitumen was blended with different PW content (C). Firstly, the optimal production condition of PW modified bitumen was determined based on orthogonal experimental analysis. Then, the conventional, viscosity-temperature, storage stability, differential scanning calorimetry, Fourier transform infrared and rheological tests were conducted to evaluate the performances of the optimal PW modified bitumen before and after aging. Results show that the optimal production condition is T = 400 °C, P = 0.5 MPa, C = 6%. After adding matrix asphalt (MA), pyrolysis waxes can be used as a colloid dispersion medium, thus reducing the viscosity of MA. In addition, the PW led to a lower penetration, a higher softening point and a lower viscosity, and ductility was still within specification. The PW modified bitumen still has better storage stability and there is no obvious chemical reaction that occurred in the PW modified bitumen. Meanwhile, the incorporation of PW enhanced the viscoelastic properties, high-temperature performance, permanent deformation resistance, short-term and long-term aging resistance ability and anti-fatigue ability as revealed by the differential scanning calorimetry and rheological tests.

Laser-irradiated carbonized polyaniline-N-doped graphene heterostructure improves the cyclability of on-chip microsupercapacitor.

Laser-irradiated graphene-based heterostructures have attracted significant attention for the fabrication of highly conducting and stable metal-free energy storage devices. Heteroatom doping on the graphene backbone has proven to have better charge storage properties. Among other heteroatoms, nitrogen-doped graphene (NG) has been extensively researched due to its several advanced properties while maintaining the original characteristics of graphene for energy storage applications. However, NG is generally prepared via chemical vapor deposition or high temperature pyrolysis method, which gives low yield and has a complex operation route. In this work, first a polyaniline-reduce graphene oxide (PANI-rGO) heterostructure was prepared via in situ electrochemical polymerization, followed by the deposition process. In the next step, laser-irradiation process was employed to carbonize polyaniline as well as doping of nitrogen on the graphene film, simultaneously. For the very first time, laser-irradiated carbonization of PANI on NG (cPANI-NG) heterostructure was utilized for microsupercapacitor (MSC). The as-prepared cPANI-NG-MSC shows extremely high cycling stability with a capacitance enhancement of 135% of its initial capacitance after 70 000 continuous charge-discharge cycles. It is very interesting to know the origin of the capacitance enhancement, which results from the change of pyrrolic N in NG-MSC to the pyridinic and graphitic N. An on-chip NG-MSC exhibits an excellent charge storage capacitance of 43.5 mF cm-2 at a current density of 0.5 mA cm-2 and shows impressive power delivery at a very high scan rate of 100 V s-1. The excellent rate capability of the MSC shows capacitance retention up to 70.1% with the variation of current density. This unique approach to fabricate NG-MSC can have a broad range of applications as energy storage devices in the electronics market, as demonstrated by glowing a commercial red LED.

Zr enhanced Fe, N, S co-doped carbon-based catalyst for high-efficiency oxygen reduction reaction

Fe-N x catalysts have received widespread attention in recent years due to their excellent catalytic performance, hoping to replace platinum for oxygen reduction reactions (ORR). In recent years, more studies have shown that when the catalyst contains two or more metals doped, its catalytic performance will be improved. Herein, using the high temperature pyrolysis method, through the incorporation of the second phase metal (Zr), melamine as the nitrogen source, and thiourea as the sulfur source, a high-activity carbon-based catalyst doped with Fe and Zr bimetals was synthesized. Originating from the strong interaction between Fe species and ZrO 2 clusters and the promotion of O 2 adsorption by ZrO 2 nanoparticles supported on nitrogen-doped carbon, this catalyst has a better ORR electrocatalytic performance than 46% TKK commercial platinum carbon in 0.1 M KOH, exhibiting an onset potential of 1.047 V vs RHE, a half-wave potential of 0.909 V vs RHE. It provides a new idea for the preparation of high-performance bimetallic-doped carbon-based electrocatalysts. • Zr, Fe, N, S co-doped carbon-based catalyst derived from Ionic Liquids a simple method. • The catalysts possesses high active sites and porous structure. • The interaction between Fe and Zr and the abundant active group substances could greatly improve the basic ORR activity.

Recent progress in electrochemical reduction of carbon dioxide on metal single‐atom catalysts

AbstractElectrochemical reduction reaction of CO2 (CO2RR) is a promising technology for alleviating the global warming caused by the emission of CO2. This technology, however, is still in the stage of finding efficient catalysts. The catalysts must be able to convert CO2 to other carbon‐based products with high activity and selectivity to valuable chemicals. In this review, previous development of heteroatom‐doped metal‐free carbon materials (H‐CMs) is briefly summarized. Recent progress of CO2RR promoted by metal single‐atom catalysts (M‐SACs) is then discussed with emphasis on the synthesis of M‐SACs, the catalytic performance, and reaction mechanisms. The high temperature pyrolysis method and electrodeposition are attracting attentions recently to prepare M‐SACs with high metal loading on N‐doped carbon materials, a very active M‐SACs system for the CO2RR. Theoretical calculations of free energy change on active sites, the Operando X‐ray absorption near edge structure (XANES), and Bader charge analysis reveal a significant role of metal oxidation state and charge transfer between metal atoms and absorbed CO. The challenges and perspectives for the extensive applications of M‐SACs in CO2RR are also discussed in this review.

Interfacial Electronic Effects in Co@N-Doped Carbon Shells Heterojunction Catalyst for Semi-Hydrogenation of Phenylacetylene.

Metal-supported catalyst with high activity and relatively simple preparation method is given priority to industrial production. In this work, this study reported an easily accessible synthesis strategy to prepare Mott-Schottky-type N-doped carbon encapsulated metallic Co (Co@Np+gC) catalyst by high-temperature pyrolysis method in which carbon nitride (g-C3N4) and dopamine were used as support and nitrogen source. The prepared Co@Np+gC presented a Mott-Schottky effect; that is, a strong electronic interaction of metallic Co and N-doped carbon shell was constructed to lead to the generation of Mott-Schottky contact. The metallic Co, due to high work function as compared to that of N-doped carbon, transferred electrons to the N-doped outer shell, forming a new contact interface. In this interface area, the positive and negative charges were redistributed, and the catalytic hydrogenation mainly occurred in the area of active charges. The Co@Np+gC catalyst showed excellent catalytic activity in the hydrogenation of phenylacetylene to styrene, and the selectivity of styrene reached 82.4%, much higher than those of reference catalysts. The reason for the promoted semi-hydrogenation of phenylacetylene was attributed to the electron transfer of metallic Co, as it was caused by N doping on carbon.