Mesoporous Carbon Electrocatalyst Research Articles

Enhancing Hydrogen Peroxide Production through Modulating the Morphology of N-doped Mesoporous Carbon Electrocatalysts

Enhancing Hydrogen Peroxide Production through Modulating the Morphology of N-doped Mesoporous Carbon Electrocatalysts

Ni-single atom decorated mesoporous carbon electrocatalysts for hydrogen evolution reaction

A single atom catalyst (SAC) is a type of heterogeneous catalyst in which individual metal atoms are dispersed on a support material, such as carbon, metal oxides, or zeolites, rather than forming nanoparticles or clusters. SACs have unique catalytic properties, such as high selectivity and activity, due to their high surface area and the exposed active metal sites, allowing them to interact more efficiently with the reactants. SACs also have the advantage of being more environmentally friendly and cost-effective than traditional catalysts, as they require smaller amounts of metal and can be easily recycled. In this study, we report the synthetic method of mesoporous single atom catalysts (MSACs) containing nickel (Ni), platinum (Pt), iridium (Ir), cobalt (Co), and iron (Fe) as metal-centered atoms for hydrogen evolution reaction (HER). MSACs are successfully synthesized with metal-chelation and soft-templating methods. The results show that highly uniform MSACs can be fabricated with high reproducibility. The metal contents in MSACs can be reduced to under 1wt%, keeping good HER reactivity. For HER, the Ni mesoporous single atom catalysts (Ni-MSACs) show 270 mV overpotential at 10 mA/cm2 at the initial polarization curve and reduces to 190 mV after 2,000 cycles, which outperforms Ni bulk catalyst (Ni plate). In contrast, porous pure carbon without Ni atoms shows inferior performance, indicating that Ni metal center plays an important role in the catalytic activity. The computational calculation using density functional theory (DFT) tells that Volmer-Heyrovsky pathway is dominant for HER using the Ni-MSACs. The performance of MSACs has a high potential for improvement of performance and extreme reduction of metal usage by doping nitrogen, phosphorous, and two or more metal atoms into MSACs.

Mesoporous carbon-based materials and their applications as non-precious metal electrocatalysts in the oxygen reduction reaction

Carbon is truly astonishing and the only element that can form so many different compounds and materials. In recent years, numerous nanostructured carbon-based materials have emerged and within this family, mesoporous and ordered mesoporous carbon have attracted considerable attention. In this paper, we review the recent developments in the applications of mesoporous carbon as an electrocatalyst for the oxygen reduction reaction (ORR). The ORR is one of the most studied electrochemical reactions with applications in the energy and environmental sectors. Following a short introduction to the methodologies employed in the fabrication of mesoporous and ordered mesoporous carbon, the performance of these materials in the ORR is reviewed. Initially, metal free heteroatom doped mesoporous carbon electrocatalysts are described, highlighting the roles of N, S and B as dopants. Next, mesoporous carbon materials with Fe, Co, Mn and Ni, as isolated single atom catalysts, are introduced. The role of mesoporous carbon as a support for nanostructured electrocatalysts is then discussed. Finally, the selectivity of the mesoporous carbon-based electrocatalysts for the four and two-electron ORR is discussed.While further developments and advancements are needed, it is clear that these mesoporous carbon-based materials have the potential to give highly efficient electrocatalysts for both the four and two electron ORR. Indeed, many of the reported electrocatalysts can outperform the commercial Pt/carbon electrocatalysts in alkaline solutions.

Modulating the Electronic Structure of FeCo Nanoparticles in N-Doped Mesoporous Carbon for Efficient Oxygen Reduction Reaction.

The development of highly efficient and stable oxygen reduction electrocatalysts and revealing their underlying catalytic mechanism are crucial in expanding the applications of metal‐air batteries. Herein, an excellent FeCo alloy nanoparticles (NPs)‐decorated N‐doped mesoporous carbon electrocatalyst (FeCo/NC) for oxygen reduction reaction, prepared through the pyrolysis of a dual metal containing metal‐organic framework composite scaffold is reported. Benefiting from the highly exposed bimetal active sites and the carefully designed structure, the Fe0.25Co0.75/NC‐800 catalyst exhibits a promising electrocatalytic activity and a superior durability, better than those of the state‐of‐the‐art catalysts. Suggested by both the X‐ray absorption fine structures and the density functional theoretical calculation, the outstanding catalytic performance is originated from the synergistic effects of the bimetallic loading in NC catalysts, where the electronic modulation of the Co active sites from the nearby Fe species leads to an optimized binding strength for reaction intermediates. This work demonstrates a class of highly active nonprecious metals electrocatalysts and provides valuable insights into investigating the structure–performance relationship of transition metal‐based alloy catalysts.

Tailored ZnO Nanostructure Based Quasi-Solid-State Electrolyte and Mesoporous Carbon Electrocatalyst for Solar Energy Conversion

We have investigated the photoelectrochemical influence of quasi-solid-state electrolytes based on tailored ZnO nanostructures and mesoporous carbon electrocatalyst in the solar conversion performance of dye-sensitized solar cells (DSSCs). Tailored ZnO nanostructures with rod-shaped petals (ZnO nanorod) and almond-shaped petals (ZnO nanoalmond), were prepared using the hydrothermal method, respectively. Mesoporous carbon electrocatalyst with a high surface area is obtained by the carbonization of the PVDC-g-POEM double comb copolymer. The phase and structure of tailored ZnO nanostructures were investigated using scanning electron microscopy (SEM) and wide angle X-ray scattering (WAXS). Diffuse reflectance, intensity-modulated photocurrent spectroscopy (IMPS)/intensity-modulated photovoltage spectroscopy (IMVS), electrochemical impedance spectroscopy (EIS) measurements were used to investigate the optical and electrochemical properties of quasi-solid-state electrolytes. The quasi-solid-state electrolytes based on ZnO nanorod significantly improved the solar conversion performance owing to its enhanced scattering effect, ion diffusion, effective path for redox couple transfer, and sufficient penetration of quasi-solid-state electrolytes into the electrode. The quasi-solid-state electrolytes based on ZnO nanorod, ZnO nanoalmond and mesoporous carbon electrocatalyst showed a solar conversion efficiency of 6.4%, 5.4%, respectively, which is higher than that of the polymer gel electrolytes (4.7%).

Iridium‐Doped N‐Rich Mesoporous Carbon Electrocatalyst with Synthetic Macrocycles as Carbon Source for Hydrogen Evolution Reaction

AbstractUtilizing supramolecular synthetic macrocycles with distinct porous structures and abundant functional groups as a precursor for metal‐doped carbon electrocatalysts can endow the resulting materials with great potential in electrocatalysis. Herein, iridium‐doped electrocatalysts (CBC‐Ir), using a synthetic macrocycle named cucurbit[6]uril as the carbon source precursor, are designed and prepared. Interestingly, owing to the numerous N‐containing backbone and unique porous structure from cucurbit[6]uril self‐assembly, the newly designed catalysts CBC‐Ir possess abundant N‐doped and mesoporous structures without the need of additional N sources and templates. The catalysts exhibit superior catalytic performance toward the hydrogen evolution reaction with high Faradaic efficiency (91.5% and 92.7%), superior turnover frequency (2.1 and 0.69 H2 s−1) at the 50 mV overpotential, and only 17 and 33 mV overpotentials in acidic and alkaline conditions reaching the current density of 10 mA cm−2, better than the commercial Pt/C (28 and 43 mV). This work not only expands the application of supramolecular macrocycles in the water splitting field but also provides a new approach for preparing robust electrocatalysts.

Selective conversion of nitrate to nitrogen by CuNi alloys embedded mesoporous carbon with breakpoint chlorination

The electrocatalytic reduction of nitrate, a common contaminant in surface and ground water, to the harmless nitrogen gas is a promising technology that can be potentially energy efficient and environmentally friendly. The bottleneck hindering its large-scale implementation is mainly attributed to the unsatisfactory selectivity toward the final product N2. To solve this challenge, a two-step strategy was applied here, in which the NO3− was first reduced to NH4+ at the cathode, followed with a rapid non-electrochemical oxidation to N2 by the ClO− generated from anodic breakpoint chlorination. Note that the formation of ClO− may be easily controlled and enhanced by the dosage of Cl− ions, the overall nitrate removal efficiency for the above process was determined by its NO3− to NH4+ activity. The high-performance copper-nickel alloys embedded mesoporous carbon electrocatalysts were therefore rationally designed, which exhibited a complete conversion of NO3− in the absence of Cl−, and furthermore, a 100% N2 selectivity with the addition of Cl−. Using density functional theory calculations, it was verified that the incorporation of Ni atoms into Cu interface significantly enhanced the adsorption of *NHOH and *NH2OH intermediates, lowering the barrier of *NOH hydrogenation to *NH3 (NH4+). Besides, the nitrogen-containing ordered mesoporous carbon support not only facilitated the synthesis of uniformly distributed CuNi nanoparticles (ca. 20 nm), but also ensured the sufficient mass and charge transfer, as well as the high durability.

Shape-Controlled TiO2 Nanomaterials-Based Hybrid Solid-State Electrolytes for Solar Energy Conversion with a Mesoporous Carbon Electrocatalyst.

One-dimensional (1D) titanium dioxide (TiO2) is prepared by hydrothermal method and incorporated as nanofiller into a hybrid polymer matrix of polyethylene glycol (PEG) and employed as a solid-electrolyte in dye-sensitized solar cells (DSSCs). Mesoporous carbon electrocatalyst with a high surface area is obtained by the carbonization of the PVDC-g-POEM double comb copolymer. The 1D TiO2 nanofiller is found to increase the photoelectrochemical performance. As a result, for the mesoporous carbon-based DSSCs, 1D TiO2 hybrid solid-state electrolyte yielded the highest efficiencies, with 6.1% under 1 sun illumination, in comparison with the efficiencies of 3.9% for quasi solid-state electrolyte and 4.8% for commercial TiO2 hybrid solid-state electrolyte, respectively. The excellent photovoltaic performance is attributed to the improved ion diffusion, scattering effect, effective path for redox couple transfer, and sufficient penetration of 1D TiO2 hybrid solid-state electrolyte into the electrode, which results in improved light-harvesting, enhanced electron transport, decreased charge recombination, and decreased resistance at the electrode/electrolyte interface.

Molecular-Level Synthesis of Cobalt Phosphide Nanocrystals Confined in Highly Nitrogen-Doped Mesoporous Carbon Electrocatalyst for Highly Efficient Dye-Sensitized Solar Cells

Developing an efficient synthetic approach for the accurate synthesis of nonprecious metal counter electrode (CE) electrocatalysts with superior catalytic activity and electrochemical stability is ...

Recycling the Catalyst of Atom Transfer Radical Polymerization to Prepare a Cu, N Codoped Mesoporous Carbon Electrocatalyst for Oxygen Reduction

Non-noble metal and nitrogen codoped carbon catalysts are considered as the alternative options for Pt-based materials for the cathodic oxygen reduction reaction (ORR). Atom transfer radical polyme...

Boron-, Phosphorus-Doped Ordered Mesoporous Carbon Electrocatalysts for the Reduction of CO2 to Formic Acid

Electrocatalytic reduction of CO2 stands out a promising approach towards carbon recycling since value-added chemicals and fuels can be produced at desired conditions. In recent decades, electrocatalytic reduction of CO2 has been extensively studied1-3, however development of effective materials capable of selectively reducing CO2 to formic acid (HCOOH) at low overpotentials is still on going. Metal-free electrocatalysts are the ideal candidates as next-generation, renewable materials that hold cost-effective and high-performance catalysts replacing precious metal catalysts. In particular, ordered mesoporous carbon channels as nano-reactor promote efficient diffusion path for CO2 access to the catalytic sites, improving the catalytic performance and Faradaic yield4. In this regard, we report here the synthesis of environmentally benign and active metal-free B- and P-doped ordered mesoporous carbon electrocatalysts and their performance towards CO2 reduction into formic acid in a batch electrolyzer. The B- and P- doped ordered mesoporous carbon (B-OMC and P-OMC) materials were prepared using SBA-15 silica as hard template and display high specific surface area (626 and 541 m2g-1), with narrow pore size distribution in the mesopore range (4.7 and 5.8 nm, respectively). A new two-step nanocasting strategy for obtaining highly effective ordered mesoporous carbons is also discussed5. Cyclic voltammetry measured under CO2 on the P-OMC electrode surface evidenced a broad peak centred at -1.20V (vs. Ag/AgCl sat. KCl) attributed to CO2 electroreduction (as confirmed by the absence of the peak if the voltammogram was measured under N2 (Fig.1). Further, the electrolysis of CO2 was investigated at controlled-potentials ranging between -1.40V and -1.80V (vs. Ag/AgCl) in a home-made two-compartment (H-type) cell. The Faradaic efficiency (F.E.) towards HCOOH was observed at -1.60 V (vs. Ag/AgCl), and reached at ca. 22% with an electrode loading of 2.38 mg cm-2 (inset Fig.1). Our recent efforts and findings, including development of nanostructured doped mesoporous carbon materials, and designing and constructing efficient electrochemical testing systems, prove that metal-free B- and P-doped ordered mesoporous carbon materials capable of selective reducing CO2 into formic acid, which is the target of the H2020 RECODE project in which this research is embedded. Acknowledgements This work was conducted in the framework of the RECODE project funded within the European Union`s Horizon 2020 Research and Innovation Programme under Grant Agreement No 768583. A postdoctoral fellowship to Dr. Nihat Şahin is gratefully acknowledged. References N. Yang, S. R. Waldvogel, X. Jiang. ACS Appl. Mater. Interfaces, (2016), 8, 28357.K. P. Kuhl, E. R. Cave, D. N. Abram, T. F. Jaramillo, Energy Environ. Sci., (2012), 5, 7050.X. Lu, D. Y. C. L. H. Wang, M. K. H. L. J. Xuan, ChemElectroChem, (2014), 5, 836.N. E. Şahin, C. Comminges, A. Le Valant, J. Kiener, J. Parmentier, T. Napporn, G. Melinte, O. Ersen, K. B. Kokoh, ChemPhysChem, (2018), 11, 1371.X. Sheng, N. Daems, B. Geboes, M. Kurttepeli, S. Bals, T. Breugelmans, A. Hubin, I. F.J. Vankelecom, P. P. Pescarmona, Appl. Catal. B: Environ. (2015), 176–177, 212. Figure 1

Deriving Efficient Porous Heteroatom‐Doped Carbon Electrocatalysts for Hydrazine Oxidation from Transition Metal Ions‐Coordinated Casein

AbstractIn this work, the synthesis of high‐performance, metal ion‐imprinted, mesoporous carbon electrocatalysts for hydrazine oxidation reaction (HzOR) using casein or a family of phosphoproteins derived from cow's milk as a precursor is shown. The synthesis is made possible by mixing trace amounts of non‐noble metal ions (Fe3+ or Co2+) with casein and then producing different metal ions‐functionalized casein intermediates, which upon carbonization, followed by acid treatment, lead to metal ion‐imprinted catalytically active sites on the materials. The materials effectively electrocatalyze HzOR with low overpotentials at neutral pH and exhibit among the highest electrocatalytic performances ever reported for carbon catalysts. Their catalytic activities are also better than the corresponding control material, synthesized by carbonization of pure casein and other materials previously reported for HzOR. This work demonstrates a novel synthetic route that transforms an inexpensive protein to highly active carbon‐based electrocatalysts by modifying its surfaces with trace amounts of non‐noble metals. The types of metal ions employed in the synthesis are found to dictate the electrocatalytic activities of the materials. Notably, Fe3+ is found to be more effective than Co2+ in helping the conversion of casein into more electrocatalytically active carbon materials for HzOR.

A template-directed bifunctional NiSx/nitrogen-doped mesoporous carbon electrocatalyst for rechargeable Zn–air batteries

A highly ordered mesoporous NiSx/nitrogen-doped mesoporous carbon (NiSx/NMC) nanohybrid as a bifunctional oxygen electrocatalyst for rechargeable Zn–air batteries.

Bimetal- and nitrogen-codoped spherical porous carbon with efficient catalytic performance towards oxygen reduction reaction in alkaline media

Nonprecious-metal electrocatalysts have been intensively investigated, but how to keep a balance between their sustainability and competitive performance for the oxygen reduction reaction (ORR) is still a big challenge for energy applications. In this work, a type of bimetal- and nitrogen-codoped mesoporous carbon electrocatalyst (FeCo-N/C-800) was successfully synthesized via a simple hydrothermal method, followed by a calcination process at 800 °C in nitrogen atmosphere and an acid-etching process. The obtained FeCo-N/C-800 can act as a high-performance ORR catalyst with high onset and half-wave potentials (0.94 and 0.85 V), a large limiting current density (5.94 mA cm−2) and a four-electron reaction process in 0.1 M KOH solution, which can be comparable with commercial Pt/C catalyst. Additionally, the FeCo-N/C-800 exhibited superior long-term durability and high methanol tolerance. The excellent electrocatalytic performance of the FeCo-N/C-800 can be ascribed to the mesoporous structure (bimodal pores system), the synergetic interaction of the multiple ORR active sites, suitable N-doping level and the highly conductive carbon matrix. These structural features can promote efficiently the mass and electron transfer, provide abundant active sites for the adsorption and reaction of oxygen molecules, and thus improve the reaction kinetics. The present study not only provides a strategy for the synthesis of carbon-based electrocatalyst with high ORR catalytic activity and stability, but also demonstrates that the bimetal- and nitrogen-codoped carbon materials could be a class of competitive candidate for non-noble metal-based electrocatalysts.

Copper nanoparticles/polyaniline-derived mesoporous carbon electrocatalysts for hydrazine oxidation

Copper nanoparticles-decorated polyaniline-derived mesoporous carbon that can serve as noble metal-free electrocatalyst for the hydrazine oxidation reaction (HzOR) is synthesized via a facile synthetic route. The material exhibits excellent electrocatalytic activity toward HzOR with low overpotential and high current density. The material also remains stable during the electrocatalytic reaction for long time. Its good electrocatalytic performance makes this material a promising alternative to conventional noble metal-based catalysts (e.g., Pt) that are commonly used in HzOR-based fuel cells.

Vanadium Redox Flow Battery Using Electrocatalyst Decorated with Nitrogen-Doped Carbon Nanotubes Derived from Metal-Organic Frameworks

Highly porous zeolitic-imidazole frameworks (ZIFs) are synthesized to produce N-doped mesoporous carbon electrocatalysts via calcination. The N-doped carbon (m-NC) and carbon nanotubes (m-NCNT) are obtained from ZIF-8 and ZIF-67, while the core-shell structure of ZIF-8@ZIF-67 produced with ZIF-8 seeds (m-NC@NCNT) is prepared by hydrothermal method. Chemical and optical evaluations of the catalysts are characterized using BET, FT-IR, XPS, XRD, Raman spectroscopy and SEM/STEM and they are used as the catalysts for redox reactions of vanadium ions and redox flow battery (VRFB) performance. In the utilization, m-NC@NCNT and m-NCNT are effective for improving VO2+/VO2+ redox reaction, although m-NC does not influence that. Even in VRFB tests using the catalysts, charge/discharge potential and energy efficiency (EE) of m-NC@NCNT and m-NCNT are highest, not to mention excellent EE resilience after undergoing tougher cycling condition. These results are due to the large graphitic-N portion of the two catalysts. Namely, electrons produced by the graphitic-N are delocalized, forming pi-conjugated system and vanadium–nitrogen transition state. This state then promotes electron transfer during VO2+/VO2+ redox reaction and VRFB performance.

Role of phosphorus in nitrogen, phosphorus dual-doped ordered mesoporous carbon electrocatalyst for oxygen reduction reaction in alkaline media

In this paper, we have investigated the role of phosphorus (P) in nitrogen (N) and phosphorus dual-doped carbon electrocatalyst for oxygen reduction reaction (ORR) in alkaline media with three samples prepared by varying the doping orders of N and P. Results show that the resultant N-POMC (first doped with P, then N) exhibits an outstanding activity for ORR in alkaline media. The mechanism leading to the improved activity is found to be associated with the orientation effect of the first doped P on the later doped N, by increasing the ratio of graphitic-N significantly. Furthermore, a portion of the first doped P can act as the doping sites and be replaced by the later doped N, called ‘self-sacrifice’ mode, which is confirmed by both experiments and density functional theory (DFT) calculations. However, this orientation effect cannot be observed in the other two dual-doped samples. In addition, experimental and DFT calculation also prove that the amount of graphitic-N is important in improving the activity for ORR. The doping strategy reported in this work is applicable to various co-doping systems in exploring the synergy effect of different dopants and improving activity for ORR.

The influence of the type of N dopping on the performance of bifunctional N-doped ordered mesoporous carbon electrocatalysts in oxygen reduction and evolution reaction

To develop more ideal bifunctional heteroatom-doped carbon electrocatalysts toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) for regenerative fuel cells and rechargeable metal–air batteries, herein, tobacco-derived N-containing ordered mesoporous carbon (N-OMC) electrocatalysts with different N species distributions are designed. Results indicate that the as-prepared N-OMC with more pyrrolic and pyridinic Ns exhibits much higher activities for the ORR and OER than N-OMC with more graphitic N in both acidic and alkaline media, suggesting that the increase of pyrrolic and pyridinic Ns favors the improvement of ORR and OER activities of the N-containing carbon catalysts, and showing a great potential for the designing of more effective, lower-cost ORR and OER bifunctional electrocatalysts for future regenerative fuel cells and rechargeable metal–air batteries.

A Metal-Amino Acid Complex-Derived Bifunctional Oxygen Electrocatalyst for Rechargeable Zinc-Air Batteries.

Bifunctional oxygen electrocatalyst: A metal-amino acid complex is developed to prepare high-performance mesoporous carbon electrocatalyst for both oxygen reduction and oxygen evolution reactions. Such prepared catalyst can be used to assemble rechargeable zinc-air batteries with excellent durability. This work represents a new route toward low-cost, highly active, and durable bifunctional electrocatalysts for cutting-edge energy conversion devices.

Synthesis of nitrogen-doped ordered mesoporous carbon electrocatalyst: Nanoconfinement effect in SBA-15 template

The effect of the pore structure of SBA-15, which is tuned by varying the hydrothermal temperature (90–150 °C), is investigated on nitrogen-doped ordered mesoporous carbon. It is found that the pore structure of SBA-15 yields effects on both the composition and the pore structure of carbon, which thereby affecting its electrocatalytic activity for the oxygen reduction reaction (ORR). XPS reveals that the nitrogen content of the template-free carbon is 2.79 at.%, while dramatically increases to 4.48, 5.01 and 4.16 at.% for the three template-aided carbon catalysts with SBA-15 synthesized at 90, 130 and 150 °C, respectively. Nitrogen ad/desorption isotherms show that the specific surface area of the template-free carbon is 257 m2 g−1, which increases to 724, 731 and 691 m2 g−1 for the above three carbons. Such changes correlate well with the electrochemical results. RRDE results show that the template-aided carbon catalysts yield better activity and selectivity for the ORR than does the template-free one. And the best performance is achieved for the carbon catalyst with SBA-15 synthesized at 130 °C, which coincidentally has the highest nitrogen content and surface area.