Electrochemical properties of boron-doped ordered mesoporous carbon as electrocatalyst and Pt catalyst support

Ultrafast Porous Carbon Activation Promises High-Energy Density Supercapacitors

Activated porous carbons (APCs) are traditionally produced by heat treatment and KOH activation, where the production time can be as long as 2 h, and the produced activated porous carbons suffer from relatively low specific surface area and porosity. In this study, the fast high-temperature shock (HTS) carbonization and HTS-KOH activation method to synthesize activated porous carbons with high specific surface area of ≈843 m² g^-1 , is proposed. During the HTS process, the instant Joule heating (at a heating speed of ≈1100 K s^-1 ) with high temperature and rapid quenching can effectively produce abundant pores with homogeneous size-distribution due to the instant melt of KOH into small droplets, which facilitates the interaction between carbon and KOH to form controllable, dense, and small pores. The as-prepared HTS-APC-based supercapacitors deliver a high energy density of 25 Wh kg^-1 at a power density of 582 W kg^-1 in the EMIMBF₄ ionic liquid. It is believed that the proposed HTS technique has created a new pathway for manufacturing activated porous carbons with largely enhanced energy density of supercapacitors, which can inspire the development of energy storage materials.

Insight into the oxidation of phenolic pollutants by enhanced permanganate with biochar: The role of high-valent manganese intermediate species

This work demonstrated that the oxidation of phenolic pollutants by permanganate (KMnO₄) was effectively enhanced by a commercial biochar. Detailed characterization data indicated that the biochar contains porous structures, amounts of defective sites and abundant redox-active groups. In the presence of biochar, the degradation efficiency of 4-nitrophenol by KMnO₄ surged from 5% to 92% in 180 min, up to 37.8% of total organic carbon (TOC) was removed. Meanwhile, acute toxicity of 4-nitrophenol was greatly reduced. Through analyzing oxidation products of triclosan (TCS) and using methyl phenyl sulfoxide (PMSO) as a chemical probe, high-valent Mn intermediates (i.e. Mn(VI)/Mn(V)) were proved to be the dominant oxidant in the KMnO₄/biochar system. Quantitative structure-activity relationships (QSARs) were established between oxidation rate constants of various substituted phenols and classical descriptor variables (i.e., Hammett constant σ⁺). KMnO₄/biochar was found to be less selective to the substituent variation of phenolic compounds compared with O₃, K₂FeO₄, ClO₂ and persulfate/carbon nanotube (PDS/CNT). This work provided a novel catalytic oxidation technology for eliminating phenolic compounds, and improved insights into the mechanistic study of the KMnO₄-based oxidation process.

Catalytic degradation of sulfamethoxazole by peroxymonosulfate activation system composed of nitrogen-doped biochar from pomelo peel: Important roles of defects and nitrogen, and detoxification of intermediates

Nitrogen doping could improve the catalytic performance of carbon materials, in which the nitrogen configuration could be used as active sites for peroxymonosulfate (PMS) activation. Herein, this paper studied how to turn waste to "treasure" by agriculture waste pomelo peel to prepare nitrogen-doped biochar and successfully applied it to advanced oxidation field. The effects of the sodium bicarbonate (NaHCO₃), melamine, and pyrolysis temperature on the catalytic activity of biochar for the removal of sulfamethoxazole (SMX) were investigated. The optimized nitrogen-doped biochar (C-N-M 1:3:4) possessed high specific surface area (SSA, 738 m²/g) and high level of nitrogen doping (nitrogen content 13.54 at%). Accordingly, it exhibited great catalytic performance for PMS activation to remove SMX antibiotic, and 95% of SMX was removed within 30 min. High catalytic activity of C-N-M 1:3:4 was attributed to rich defects, carbonyl group, high content of graphitic N and pyrrolic N, and large SSA, in which non-radical oxidation process based on singlet oxygen (¹O₂) and electron transfer contributed to the SMX degradation. The prepared nitrogen-doped biochar possessed high stability and reusability and the removal efficiency of SMX still reached 80% after four cycles. Additionally, the phytotoxicity assay indicated that the toxicity of degradation intermediates was obviously decreased in the PMS/ C-N-M 1:3:4 system.

Resolving the Tribo-catalytic reaction mechanism for biochar regulated Zinc Oxide and its application in protein transformation

The utilization of mechanical energy to control water pollutants under dark conditions is currently a point of study focus. Herein, biochar -zinc oxide (BC-ZnO) composites with various structures were synthesized by co-pyrolysis of cotton and ZnO at different temperature and used for tribo-catalytic reaction. The introduction of BC can improve charge transmission and separation efficiency. Ultraviolet photoelectron spectra (UPS) and density functional theory (DFT) calculation prove the addition of BC can reduce work function of ZnO, and enhance its electron-donating ability. Specially, suitable adsorption amount is the key factor to improve the tribo-catalytic performance. When the pyrolysis temperature is 600 °C, BC-ZnO has the best degradation efficiency, which can degrade 90% Rhodamine B (RhB) in 75 min, while ZnO can degrade only 38%. On this basis, using bovine serum albumin (BSA) as a model, the effect of tribo-catalytic reaction on controlling proteins in water was studied by fluorescence excitation-emission matrix spectroscopy (3D EEM) and infrared microscope, and the transformation of proteins was further analyzed. This study provides a new strategy to improve the tribo-catalytic performance of ZnO, and explores its application prospects of biological wastewater control.

Doping strategy, properties and application of heteroatom-doped ordered mesoporous carbon

To date, tremendous achievements have been made to produce ordered mesoporous carbon (OMC) with well-designed and controllable porous structure for catalysis, energy storage and conversion. However, OMC as electrode material suffers from poor hydrophilicity and weak electrical conductivity. Numerous attempts and much research interest have been devoted to dope different heteroatoms in OMC as the structure defects to enhance its performance, such as nitrogen, phosphorus, sulphur, boron, and multi heteroatoms. Unfortunately, the "how-why-what" question for the heteroatom-doped OMC has not been summarized in any published reports. Therefore, this review focuses on the functionalization strategies of heteroatoms in OMC and the corresponding process characteristics, including in situ method, post treatment method, and chemical vapor deposition. The fundamentally influencing mechanisms of various heteroatoms in electrochemical property and porous structure are summarized in detail. Furthermore, this review provides an updated summary about the applications of different heteroatom-doped OMC in supercapacitor, electrocatalysis, and ion battery during the last decade. Finally, the future challenges and research strategies for heteroatom-doped OMC are also proposed.

Improved Electrocatalytic Activity and Durability of Pt Nanoparticles Supported on Boron-Doped Carbon Black

A facile strategy is proposed to synthesize boron-doped ECP600 carbon black (B-ECP600), and the catalyst of Pt supported on boron-doped ECP600 (Pt/B-ECP600) shows smaller particle sizes and a higher electrochemical surface area (95.62 m2·gPt−1) and oxygen reduction reaction activity (0.286 A·mgPt−1 for mass activity; 0.299 mA·cm−2 for area specific activity) compared to the catalyst of Pt supported on ECP600 (Pt/ECP600). The results show that the boron doping of the carbon supports plays an important role in controlling the size and dispersion of Pt nanoparticles and the O2 adsorption/dissociation of the oxygen reduction reaction. A further accelerated durability test proves that boron doping can greatly enhance the stability of carbon support and thus improves the electrochemical performance of the catalyst during the long-time running. All these results suggest boron-doped carbon has great potential for application in fuel cells.

Recent advances in functionalized micro and mesoporous carbon materials: synthesis and applications

Functionalized nanoporous carbon materials have attracted the colossal interest of the materials science fraternity owing to their intriguing physical and chemical properties including a well-ordered porous structure, exemplary high specific surface areas, electronic and ionic conductivity, excellent accessibility to active sites, and enhanced mass transport and diffusion. These properties make them a special and unique choice for various applications in divergent fields such as energy storage batteries, supercapacitors, energy conversion fuel cells, adsorption/separation of bulky molecules, heterogeneous catalysts, catalyst supports, photocatalysis, carbon capture, gas storage, biomolecule detection, vapour sensing and drug delivery. Because of the anisotropic and synergistic effects arising from the heteroatom doping at the nanoscale, these novel materials show high potential especially in electrochemical applications such as batteries, supercapacitors and electrocatalysts for fuel cell applications and water electrolysis. In order to gain the optimal benefit, it is necessary to implement tailor made functionalities in the porous carbon surfaces as well as in the carbon skeleton through the comprehensive experimentation. These most appealing nanoporous carbon materials can be synthesized through the carbonization of high carbon containing molecular precursors by using soft or hard templating or non-templating pathways. This review encompasses the approaches and the wide range of methodologies that have been employed over the last five years in the preparation and functionalisation of nanoporous carbon materials via incorporation of metals, non-metal heteroatoms, multiple heteroatoms, and various surface functional groups that mostly dictate their place in a wide range of practical applications.

Surfactant-free synthesis of three-dimensional nitrogen-doped hierarchically porous carbon and its application as an electrode modification material for simultaneous sensing of ascorbic acid, dopamine and uric acid

A 3D N-doped hierarchically porous carbon modified electrode enables simultaneous sensitive detection of ascorbic acid, dopamine and uric acid.

Highly-sensitive electrochemical sensing platforms for food colourants based on the property-tuning of porous carbon

It is very challenging to develop highly-sensitive analytical platforms for toxic synthetic colourants that widely added in food samples. Herein, a series of porous carbon (PC) was prepared using CaCO3 nanoparticles (nano-CaCO3) as the hard template and starch as the carbon precursor. Characterizations of scanning electron microscopy and transmission electron microscopy indicated that the morphology and porous structure were controlled by the weight ratio of starch and nano-CaCO3. The electrochemical behaviours of four kinds of widely-used food colourants, Sunset yellow, Tartrazine, Ponceau 4R and Allura red, were studied. On the surface of PC samples, the oxidation signals of colourants enhanced obviously, and more importantly, the signal enhancement abilities of PC were also dependent on the starch/nano-CaCO3 weight ratio. The greatly-increased electron transfer ability and accumulation efficiency were the main reason for the enhanced signals of colourants, as confirmed by electrochemical impedance spectroscopy and chronocoulometry. The prepared PC-2 sample by 1:1 starch/nano-CaCO3 weight ratio was more active for the oxidation of food colourtants, and increased the signals by 89.4-fold, 79.3-fold, 47.3-fold and 50.7-fold for Sunset yellow, Tartrazine, Ponceau 4R and Allura red. As a result, a highly-sensitive electrochemical sensing platform was developed, and the detection limits were 1.4, 3.5, 2.1 and 1.7 μg L(-1) for Sunset yellow, Tartrazine, Ponceau 4R and Allura red. The practical application of this new sensing platform was demonstrated using drink samples, and the detected results consisted with the values that obtained by high-performance liquid chromatography.