Porous Carbon Anode Research Articles

Tree‐Bark‐Shaped N‐Doped Porous Carbon Anode for Hydrazine Fuel Cells

AbstractMetal‐free N‐doped porous carbon has great potential as a catalyst for hydrazine oxidation in direct hydrazine fuel cells (DHFCs). However, previous studies have reported only half‐cell characterization, and the effect of the pore size distribution has not been intensively investigated. Herein, we report the synthesis of highly active, metal‐free N‐doped carbon (NDC) by controlling the pore size distribution, and for the first time, the effect of the pore size distribution on the anode performance in a DHFC is investigated. As a result, tree‐bark‐shaped NDC with meso/macroporous (>10 nm) structures exhibit a remarkable power density of 127.5 mW cm−2 in a DHFC.

Cover Picture: Sodium Carboxymethylcellulose Derived Oxygen‐Rich Porous Carbon Anodes for High‐Performance Lithium/Sodium‐Ion Batteries (ChemElectroChem 3/2017)

The Front Cover picture shows the possibility of CMC (white balls) being used as a green binder in the anode of lithium-ion or sodium-ion batteries, employing an oxygen-containing carbon precursor to prepare oxygen-rich porous carbon (OPC, black-gray short rods), and then the carbon material can be used as the active material in the same anode. More information can be found in the Article by Y. Zhang et al. on page 500 in Issue 3, 2017 (DOI: 10.1002/celc.201600577).

Sodium Carboxymethylcellulose Derived Oxygen‐Rich Porous Carbon Anodes for High‐Performance Lithium/Sodium‐Ion Batteries

AbstractThe front cover artwork is provided by Dr. Yongzhi Zhang et al. from Sichuan University (Chengdu, China). The image shows the conversion of sodium carboxymethylcellulose (CMC) into oxygen‐rich porous carbons and their application in anodes for lithium‐/sodium‐ion batteries. Read the full text of the Article at 10.1002/celc.201600577.

Study of Electrode Structures and Redox Kinetics in Biofuel Cells

Selection of the anode-cathode electrodes materials and structure is one of the critical challenges of bio fuel cell application. They can affect the power density and columbic efficiency. Two types of bio fuel cell were studied, the Microbial Fuel Cell (MFC) and the Enzymatic Fuel Cell (EFC), where the electrode structure and kinetics are similar except for the rates of redox reaction. The electrochemical characteristics of the In the MFC the anode was inoculated with MRS broth containing Lactobacillus Cesai Shirota. Complete characterisation and optimisation of the redox kinetics will be presented. Mediators will be used to enhance electron transfer between the fuel, bacteria and electrodes to improve electrode kinetics. A fast and convenient bacterial immobilization method will be proposed as an attempt to improve the anode efficiency of a microbial fuel cell, in which bacteria will be entrapped. The electron transfer characteristics with the mediators and immobilizers shall be studied by cyclic voltammetry and SEM imaging. Enzymatic Fuel Cell is a specific type of bio fuel cell that uses enzymes as a catalyst to oxidize its fuel, instead of precious metals. Enzymatic glucose biofuel cells convert chemical energy stored in glucose into electricity. Enzymatic oxidation from complex sugar is carried out by glucose selective enzymes such as glucose oxidase (Gox) and oxygen reducing enzyme namely laccase. These reactions are highly enzyme specific and occur at relatively mild conditions (Neutral pH and ambient temperature). The specific materials and structure for the electrodes used in enzymatic fuel cell can affect the power density and columbic efficiency. This glucose EFC cell features a 3-D porous carbon anode and cathode, for high surface area for the reaction, a suitable immobilizer for the enzyme immobilization and mediators like ferrocene for optimal electron transfer. The achievable cell potential is between 0.7- 0.8V. The achieved power density is still below theoretical value. The EFC will be optimized for enzyme loading; conductive loss minimization, both electronic and ionic, direct charge transfer for improving charge transfer efficiency, and pore channel and size profile.

Sodium Carboxymethylcellulose Derived Oxygen‐Rich Porous Carbon Anodes for High‐Performance Lithium/Sodium‐Ion Batteries

AbstractSodium carboxymethylcellulose (CMC), which contains large amounts of carboxymethyl and hydroxy groups, has been used as an oxygen‐containing carbon precursor to prepare oxygen‐rich porous carbon (OPC) in a silica‐template process. CMC can be mixed homogeneously with the silica template because of its excellent water solubility and viscosity, which is one of the key reasons for the successful preparation of OPC. The obtained OPC possesses some micropores, many mesopores with different sizes, a large specific surface area of 1792.6 m2 g−1, and a high oxygen content of 8.63 wt %, and exhibits superb dual functionality as anodes for lithium‐ion and sodium‐ion batteries.

Nitrogen-rich porous carbon anode with high performance for sodium ion batteries

Nitrogen-rich porous carbon has been successfully fabricated by using the biomass of human hair as the carbon precursor through a simple chemical activation of KOH. Due to its unique porous structure and appropriate nitrogen doping, the as-prepared carbon can show high capacity (308 mAh g−1 at 100 mA g−1), superior rate capability (138 mAh g−1 at 1 A g−1), and excellent cycle stability (201 mAh g−1 after 100 cycles at 100 mA g−1). These results suggest that the porous carbon in this work could be a promising anode material for sodium ion batteries.

Biomass Inspired Nitrogen Doped Porous Carbon Anode with High Performance for Lithium Ion Batteries

AbstractGinkgo leave, a naturally abundant resource, has been successfully employed as the raw material to prepare nitrogen doped porous carbon (NDPC) materials. The preparation of the porous carbon does not involve assistance of any activation or template technique. The as‐obtained NDPC shows favorable features for electrochemical energy storage, which can not only provide multiple sites for the storage and insertion of Li ions, but also facilitate rapid mass transport of electrons and Li ions. As a result, the NDPC when evaluated as an anode material for lithium ion batteries delivers high reversible capacity (505 mAh·g−1 at 0.1 C), excellent rate capability (190 mAh·g−1 at 10 C). These favorable properties suggest that the NDPC can be a promising anode material for lithium ion batteries (LIBs).

Natural gas anodes for aluminium electrolysis in molten fluorides

Industrial primary production of aluminium has been developed and improved over more than 100 years. The molten salt electrolysis process is still suffering from low energy efficiency and considerable emissions of greenhouse gases (CO2 and PFC). A new concept has been suggested where methane is supplied through the anode so that the CO2 emissions may be reduced significantly, the PFC emissions may be eliminated and the energy consumption may decrease significantly. Porous carbon anodes made from different graphite grades were studied in controlled laboratory experiments. The anode potential, the anode carbon consumption and the level of HF gas above the electrolyte were measured during electrolysis. In some cases it was found that the methane oxidation was effectively participating in the anode process.

An Advanced Lithium Ion Battery Based on a Sulfur-Doped Porous Carbon Anode and a Lithium Iron Phosphate Cathode

An S-doped porous carbon (SPC) with a pillar-supported porous layer structure is prepared by carbonizing petroleum asphalt adsorbed on porous MgO-MgSO4 composite layers. As anode for a half cell, the SPC presents high Li storage capacity and excellent cycling stability (100 cycles without capacity decay), markedly superior to those of the N-doped porous carbon (NPC) and the undoped porous carbon (PC). Coin type full cells with SPC as anode and LiFePO4 (LFP) as cathode (SPC/LFP) are assembled and tested, which afford a high reversible capability (161mAhg−1 at 0.2C based on the mass of cathode) with a capacity retention of 96.8% after 100 cycles at 1C, indicating a superior cycling stability as compared to the previously-reported graphene/LFP cells. State-of-charge estimation with satisfying error tolerance is realized in the SPC/LFP full cell. These unique features of SPC suggest a practical substitution of graphite as a high performance anode material in LIBs and broaden roads to hybrid devices with reliable battery management systems.

Stretchable glucose biofuel cell with wirings made of multiwall carbon nanotubes

In this study, we fabricated a flexible and stretchable glucose-biofuel cell with wirings made of multi wall carbon nanotube (MWCNTs) on a polydimethylsiloxane substrate. The biofuel cell investigated consists of a porous carbon anode (area of 30 mm2) modified by glucose oxidase and ferrocene, and a cathode (area of 30 mm2) modified by bilirubin oxidase. The anode and the cathode were connected with the MWCNT wirings. The maximum power of 0.31 μW at 76.6 mV, which corresponds to a power density of 1.04 μW/cm2, was realized by immersing the biofuel cell in a phosphate buffer solution with a glucose concentration of 100 mM, at room temperature.

Integration of Glucose Biofuel Cells with a MEMS Diaphragm Micropump

Enzymatic biofuel cells (BFCs) that utilize enzymes as electrocatalysts instead of metals have attracted attention as ubiquitous sustainable power devices that can generate electricity directly from the blood or bodily fluids [1]. A characteristic feature of BFCs is their ability to generate power using various kinds of fuels, such as glucose, lipids, and hydrogen. In other words, a wide range of fuel choices is possible because they do not require an ion-exchange membrane. Many biofuel cells are safe and biocompatible, utilizing enzymes as biological catalysts. In addition, they function under mild conditions from room temperature to human body temperature under neutral pH conditions. Microelectromechanical system (MEMS) technologies have been applied to realize compact, high-output power sources toward the commercialization of BFCs. For example, Choban et al. reported a BFC with a Y-shaped channel that used formic acid and oxygen [2]. It utilized laminar flows of the two fuels without mixing for efficient reactions at each electrode. Togo et al. built hydrophobic pillars in a flow path, and fed air individually into three cells [3]. Fukushi et al. reported a flexible biofuel cell equipped with a microchannel which mimicked the blood vessels in the human body [4]. However, these biofuel cells equipped with microchannels require large external flow systems that include tubing and pumps to supply the fuels. Compact fuel transport mechanisms would be more desirable. Micropumps fabricated with MEMS technology have been considered for use in such fuel transport mechanisms [5,6]. Liu et al. reported polyimide (PI) diaphragm micropumps (15 × 15 mm2) fabricated using MEMS technology [7]. Such micropumps should be able to deliver enough glucose fuel solution to continuously generate power in a BFC. In this paper, a new BFC equipped in the fluid reservoir of the micropump is reported, and its power generation performance and lifetime are discussed. We fabricated a micropump with a polyimide (PI) diaphragm (53 μm thick, 7 mm diameter) on a silicon chip using microfabrication processes, and a glucose biofuel cell was inserted into the fluid chamber of the micropump. The biofuel cell was fabricated on another PI film, with glucose oxidase immobilized on its porous carbon anode and bilirubin oxidase immobilized on the porous carbon cathode. Each semicircular electrode area was 14.1 mm2 with a radius of 3 mm, and the gap between the anode and cathode was 1 mm. The device generated electricity by feeding an aqueous solution of glucose directly onto the electrodes in the micropump chamber. The maximum generated power, 0.076 μW at 98 mV, corresponding to a power density of 0.556 μW/cm2, was realized when a 100 mM glucose solution was introduced under diaphragm pressures alternating between 0 and 30 kPa at a pumping frequency of 3 Hz. A longer power generation lifetime was observed under fuel flow driven by micropump operation. [1] H. Becker and U. Heim, Sensors Actuators: A Phys., 83 (2000) 130. [2] E. R. Choban, J. S. Spendelow, L. Gancs, A. Wieckowski and P. J. Kenis, Electrochim. Acta, 50 (2005) 5390. [3] M. Togo, K. Morimoto, T. Abe, H. Kaji and M. Nishizawa, TRANSDUCERS 2009–15th Int. Conf. Solid-State Sensors, Actuators Microsystems (2009) pp. 2102–2105. [4] Y. Fukushi, S. Koide, R. Ikoma, W. Akatsuka, S. Tsujimura and Y. Nishioka, J. Photopolym. Sci. Technol., 26 (2013) 303. [5] A. Zebda, L. Renaud, M. Cretin, C. Innocent, F. Pichot, R. Ferrigno and S. Tingry, J. Power Sources, 193 (2009) 602. [6] W. L. Benard, H. Kahn, A. H. Heuer and M. A. Huff, J. Microelectromechanical Syst., 7 (1998) 245. [7] Y. Liu, H. Komatsuzaki, S. Imai and Y. Nishioka, Sens. Actuators A: Phys., 169 (2011) 259.

A Single-Use Paper-Shaped Microbial Fuel Cell for Rapid Aqueous Biosensing.

The traditional chamber-based microbial fuel cell (MFC) often has the disadvantages of high ohmic resistance, large volume requirements, and delayed start-up. In this study, paper-shaped MFCs utilizing a porous carbon anode, a solid Ag2 O-coated carbon cathode, and a micrometer-thin porous polyvinylidene fluoride (PVDF) separator are investigated to address the classical MFC issues. The Ag2 O-coated cathode has a low overpotential of 0.06 V at a reducing current of 1 mA compared to a Pt-air cathode. Rapid inoculation by filtration results in an instantaneous power density of 92 mW m(-2) with an internal resistance of 162 Ω. Integrated current over the first 30 min of operation has a linear relation with microbial concentration.

Stretchable Biofuel Cells with Silver Nanowiring on a Polydimethylsiloxane Substrate

In this study, we fabricated a flexible, stretchable glucose-biofuel cell with silver nanowires (AgNWs) on a dimethylpolysiloxane substrate. The biofuel cell investigated consists of a porous carbon anode (area of 30 mm2) modified by glucose oxidase and ferrocene, and a cathode (area of 30 mm2) modified by bilirubin oxidase. The anode and the cathode were connected with AgNWs. The maximum power of 0.29 μW at 180 mV, which corresponds to a power density of 0.98 μW/cm2, is realized by immersing the biofuel cell in a phosphate buffer solution with a glucose concentration of 100 mM, at room temperature.

Rechargeable PEM Fuel-Cell Batteries Using Porous Carbon Modified with Carbonyl Groups as Anode Materials

Rechargeable fuel-cell batteries (RFCBs) operate by hydrogen storage and release at the anode, while oxygen evolution and reduction reactions occur at the cathode. High-surface-area porous carbon was treated with HNO3 to produce an anode material with carbonyl and phenol groups on the surface, thereby providing redox sites for hydrogen storage and release. The HNO3-activated carbon anodes were characterized with respect to use in a RFCB operated from room temperature to 75°C with a voltage range of 0–2.0 V. The quantity of carbonyl groups and the corresponding reduced phenol groups increased with the O/C atomic ratio of the oxygenated carbon, by which the electrical capacity was increased to reach a maximum of 125 mAh g−1 at an O/C atomic ratio of 0.114. The optimal temperature and charge voltage for performance and cyclability were determined to be 50°C and 1.25 V, respectively. The charge and discharge times remained at ca. 93% of the respective initial values after 300 cycles. The RFCB with the modified porous carbon anode provided energy densities of 2.5–13.8 Wh kg−1 and power densities of 46.4–296.3 W kg−1 (normalized according to the mass of the entire cell).

Producing hierarchical porous carbon monoliths from hydrometallurgical recycling of spent lead acid battery for application in lithium ion batteries

An environmentally clean process to recycle the paste from a spent lead acid battery (LAB) is further developed to produce a porous carbon anode material for a lithium ion battery (LIB) which is under increasing focus as the solution for future energy storage and distribution networks.

Porous carbon anodes for a high capacity lithium-ion battery obtained by incorporating silica into benzoxazine during polymerization.

Porous carbon anodes with a controllable Vmes/Vmic ratio were synthesized through the self-assembly of poly(benzoxazine-co-resol) and the simultaneous hydrolysis of tetraethyl orthosilicate (TEOS) followed by carbonization and removal of silica. The Vmes/Vmic ratio of the carbon can be controlled in the range of approximately 1.3-32.6 through tuning the amount of TEOS. For lithium-ion battery anodes, a correlation between the electrochemical performance and Vmes/Vmic ratio has been established. A high Vmes/Vmic ratio in porous carbons is favorable for enhancing the accessibility of Li ions to active sites provided by the micropores and for achieving good lithium storage performance. The obtained porous carbon exhibits a high reversible capacity of 660 mAh g(-1) after 70 cycles at a current density of 100 mA g(-1). Moreover, at a high current density of 3000 mA g(-1), the capacity still remains at 215 mAh g(-1), showing a fast charge-discharge potential. This synthesis method relying on modified benzoxazine chemistry with the hydrolysis of TEOS may provide a new route for the development of mesoporous carbon-based electrode materials.

Porous Carbon Anodes for the Supply of Methane during Electrowinning of Aluminium

Currently consumable carbon anodes are utilized in the aluminium production process. The major drawback of this type of anodes is the high amount of CO2 emissions. Furthermore, due to the consumption of the anodes during the electrolysis it is necessary to adjust the anode – cathode distance continuously and finally replace the anode. Introduction of hydrogen or natural gas through the anode can decrease the CO2 emissions significantly and reduce the consumption of the anode. The use of inert porous anodes is interesting since the energy demand will be reduced due to natural gas/hydrogen participating in the anode reaction. However, due to unavailability of a sufficiently inert anode for aluminium electrolysis until now, carbon anodes seem to be more attractive. When natural gas/hydrogen is purged through the porous carbon anode, there will be competing anodic reactions depending on whether carbon from the anode or the CH4/H2 reacts with the oxygen ions from the bath. Previous studies using porous carbon anodes showed 0.3 V depolarization as well as 20% decrease in carbon anode consumption using methane compared to passing argon through the anode1. On the other hand, using CH4/H2 can lead to the formation and evolution of additional hydrogen fluoride. This was studied before and some ideas on how to deal with this extra HF evolution were presented2. In this study, further laboratory experiments were performed and the effect of carbon anodes with different porosities and designs were studied. Besides, off-gas analysis was performed and HF evolution will be discussed.

Hierarchical porous nickel oxide–carbon nanotubes as advanced pseudocapacitor materials for supercapacitors

Hierarchical porous carbon anode and metal oxide cathode are promising for supercapacitor with both high energy density and high power density. This Letter uses NiO and commercial carbon nanotubes (CNTs) as electrode materials for electrochemical capacitors with high energy storage capacities. Experimental results show that the specific capacitance of the electrode materials for 10%, 30% and 50% CNTs are 279, 242 and 112F/g, respectively in an aqueous 1M KOH electrolyte at a charge rate of 0.56A/g. The maximum specific capacitance is 328F/g at a charge rate of 0.33A/g.

Electrochemical Activation of Nitrate Reduction to Nitrogen by Ochrobactrum sp. G3-1 Using a Noncompartmented Electrochemical Bioreactor

A denitrification bacterium was isolated from riverbed soil and identified as Ochrobactrum sp., whose specific enzymes for denitrification metabolism were biochemically assayed or confirmed with specific coding genes. The denitrification activity of strain G3-1 was proportional to glucose/nitrate balance, which was consistent with the theoretical balance (0.5). The modified graphite felt cathode with neutral red, which functions as a solid electron mediator, enhanced the electron transfer from electrode to bacterial cell. The porous carbon anode was coated with a ceramic membrane and cellulose acetate film in order to permit the penetration of water molecules from the catholyte to the outside through anode, which functions as an air anode. A non-compartmented electrochemical bioreactor (NCEB) comprised of a solid electron mediator and an air anode was employed for cultivation of G3-1 cells. The intact G3-1 cells were immobilized in the solid electron mediator, by which denitrification activity was greatly increased at the lower glucose/nitrate balance than the theoretical balance (0.5). Metabolic stability of the intact G3-1 cells immobilized in the solid electron mediator was extended to 20 days, even at a glucose/nitrate balance of 0.1.

Toward a 3-D Nanostructured Battery

Nanostructured Li-ion battery electrodes were created by methods based on template-synthesis. A nanofiber V2O5 cathode, a nanocomposite LiFePO4/carbon cathode, and a porous honeycomb carbon anode were characterized structurally and electrochemically. These electrodes show dramatically improved ability to deliver specific capacity (mAh g^-1) at extreme discharge conditions compared to microstructured control electrodes. The synthesis and characterization of these electrodes is discussed in the context of the goal of a three-dimensional (3-D) nanostructured battery.