Reduced Graphene Oxide-Supported SrV4O9 Microflowers with Enhanced Electrochemical Performance for Sodium-Ion Batteries.

Sodium-ion batteries (SIBs) have received considerable attention in recent years. Anode material is one of the key factors that determine SIBs' electrochemical performance. Current commercial hard carbon anode shows poor rate performance, which greatly limits applications of SIBs. In this study, a novel vanadium-based material, SrV4O9, was proposed as an anode for SIBs, and its Na+ storage properties were studied for the first time. To enhance the electrical conductivity of SrV4O9 material, a microflower structure was designed and reduced graphene oxide (rGO) was introduced as a host to support SrV4O9 microflowers. The microflower structure effectively reduced electron diffusion distance, thus enhancing the electrical conductivity of the SrV4O9 material. The rGO showed excellent flexibility and electrical conductivity, which effectively improved the cycling life and rate performance of the SrV4O9 composite material. As a result, the SrV4O9@rGO composite showed excellent electrochemical performance (a stable capacity of 273.4 mAh g-1 after 200 cycles at 0.2 A g-1 and a high capacity of 120.4 mAh g-1 at 10.0 A g-1), indicating that SrV4O9@rGO composite can be an ideal anode material for SIBs.

Characteristics, kinetics, infrared analysis and process optimization of co-pyrolysis of waste tires and oily sludge.

The ecology was severely harmed by waste tires (WT) and oily sludge (OS). The OS and WT combinations' co-pyrolysis features, synergistic effects, and gas products were studied using thermogravimetric-infrared spectroscopy (TG-FTIR). To study kinetics and optimize pyrolysis, the Coats-Redfern and response surface methods were used. The results revealed that the OS and WT co-pyrolysis has synergistic effects. The major pyrolysis temperature range and the pyrolysis residual rate increased as the heating rate increased, and the E of the reaction increased. The strength of small-molecular-gases precipitation was modified by increasing the ratio of WT to OS, which increased OS pyrolysis. CH4, CO2, CO, and H2O are the most common gas products. The minimum estimated E and residual amount were 40.599 kJ/mol and 39.33%, respectively, when the WT mixture ratio was 58.7% and the heating rate was 10 °C/min. All the study contributes basic data to the development of the treatment of OS and WT in collaboration.

Au-TiO2/Ti Hybrid Coating as a Liquid and Gas Diffusion Layer with Improved Performance and Stability in Proton Exchange Membrane Water Electrolyzer.

The liquid and gas diffusion layer is a key component of proton exchange membrane water electrolyzer (PEMWE), and its interfacial contact resistance (ICR) and corrosion resistance have a great impact on the performance and durability of PEMWE. In this work, a novel hybrid coating with Au contacts discontinuously embedded in a titanium oxidized layer was constructed on a Ti felt via facile electrochemical metallizing and followed by a pre-oxidization process. The physicochemical characterizations, such as scanning electron microscopy, energy dispersive spectrometer, and X-ray diffraction results confirmed that the distribution and morphology of the Au contacts could be regulated with the electrical pulse time, and a hybrid coating (Au-TiO2/Ti) was eventually achieved after the long-term stability test under anode environment. At the compaction force of 140 N cm-2, the ICR was reduced from 19.7 mΩ cm2 of the P-Ti to 4.2 mΩ cm2 of the Au-TiO2/Ti. The corrosion current density at 1.8 V (RHE) is 0.689 µA cm-2. Both the ICR and corrosion resistance results showed that the prepared protective coating could provide comparable ICR and corrosion resistance to a dense Au coating.

Dense Pt Nanowire Electrocatalyst for Improved Fuel Cell Performance Using a Graphitic Carbon Nitride-Decorated Hierarchical Nanocarbon Support.

An innovative strategy is presented to engineer supported-Pt nanowire (NW) electrocatalysts with a high Pt content for the cathode of hydrogen fuel cells. This involves deposition of graphitic carbon nitride (g-CN) onto 3D multimodal porous carbon (MPC) (denoted as g-CN@MPC) and using the g-CN@MPC as an electrocatalyst support. The protective coating of g-CN on the MPC provides good stability for the electrocatalyst support against electrochemical oxidation, and also enhances oxygen adsorption and provides additional active sites for the oxygen reduction reaction. Compared with commercial carbon black Vulcan XC-72R (denoted as VC) support material, the larger hydrophobic surface area of the g-CN@MPC enables the supported high-content Pt NWs to disperse uniformly on the support. In addition, the unique 3D interconnected pore networks facilitate improved mass transport within the g-CN@MPC support material. As a result, the g-CN@MPC-supported high-content Pt catalysts show improved performance with respect to their counterparts, namely, MPC, VC, and g-CN@VC-supported Pt NW catalysts and the conventional Pt nanoparticle (NP) catalyst (i.e., Pt(20 wt%)NPs/VC (Johnson Matthey)) used as the benchmark. More importantly, the g-CN-tailored high-content Pt NW (≈60 wt%) electrocatalyst demonstrates high PEM fuel cell power/performance at a very low cathode catalyst loading (≈0.1 mgPt  cm-2 ).

Response surface optimization, combustion characteristics and kinetic analysis of mixed fuels of Fenton/CaO conditioned municipal sewage sludge and rice husk.

The co-combustion characteristics and kinetics of Fenton/CaO conditioned MSS, and biomass rice husk (RH) are studied by thermogravimetry, and the condition optimization was carried out by response surface methodology (RSM). The results show that the mixed fuel with RH is helpful to decrease Ti and Tb values and increase combustion characteristic index (CCI). The CCI of MSS after conditioning is 0.59-0.88 times lower than that of the pure MSS. In addition, the total Em of S2, MSS/RH mixed combustion after Fenton/CaO conditioning is lower, the combustion reactivity is stronger. According to RSM, the optimum conditions are considered to be: RH mixing ratio 56%, Fenton/CaO conditioner dosage 147 mg g-1 dry solids, heating rate 30 K min-1, the maximum CCI 25.3305 × 10-7%2 °C-3 min-2, and the minimum Em 10.6403 kJ min-1. This study supplies new insights into combustion technology of sludge.

PtSe2 /Pt Heterointerface with Reduced Coordination for Boosted Hydrogen Evolution Reaction.

PtSe2 is a typical noble metal dichalcogenide (NMD) that holds promising possibility for next-generation electronics and photonics. However, when applied in hydrogen evolution reaction (HER), it exhibits sluggish kinetics due to the insufficient capability of absorbing active species. Here, we construct PtSe2 /Pt heterointerface to boost the reaction dynamics of PtSe2 , enabled by an in situ electrochemical method. It is found that Se vacancies are induced around the heterointerface, reducing the coordination environment. Correspondingly, the exposed Pt atoms at the very vicinity of Se vacancies are activated, with enhanced overlap with H 1s orbital. The adsorption of H. intermediate is thus strengthened, achieving near thermoneutral free energy change. Consequently, the as-prepared PtSe2 /Pt exhibits extraordinary HER activity even superior to Pt/C, with an overpotential of 42 mV at 10 mA cm-2 and a Tafel slope of 53 mV dec-1 . This work raises attention on NMDs toward HER and provides insights for the rational construction of novel heterointerfaces.

Tourmaline-Modified FeMnTiO x Catalysts for Improved Low-Temperature NH3-SCR Performance.

Low temperature NH3 selective catalytic reduction (NH3-SCR) technology is an efficient and economical strategy for cutting NO x emissions from power-generating equipment. In this study, a novel and highly efficient NH3-SCR catalyst, tourmaline-modified FeMnTiO x is presented, which was synthesized by a simple one-step sol-gel method. We found that the amount of tourmaline has an important impact on the catalytic performance of the modified FeMnTiO x-based catalysts, and the NO x conversion exceeded 80% from 160 to 380 °C with the addition of 5 wt % tourmaline. Compared with the pure FeMnTiO x, the catalytic efficiency at a temperature below 100 °C was increased by nearly 18.9%, and the operation temperature window was broadened significantly. The enhanced catalytic performance of the FeMnTiO x catalyst was mainly attributed to the small spherical nanoparticles structure around the tourmaline powders, resulting in the increased content of Mn3+, Mn4+, and chemical oxygen on the catalytic surface. These as-developed tourmaline-modified FeMnTiO x materials have been demonstrated to be promising as a new type highly efficient low temperature NH3-SCR catalyst.

Biomass-derived nanostructured carbons and their composites as anode materials for lithium ion batteries.

Since ever-increasing energy demands stimulated intensive research activities on lithium-ion batteries (LIBs), biomass as an earth-abundant renewable energy source has played an intriguing and promising role in developing sustainable biomass-derived carbons and their composite materials for high-performance LIB anodes. Different from other materials (e.g., silicon, tin, metal oxides, etc.), biomass-derived carbons and their composite materials have been applied more and more to LIBs due to their advantages such as low cost, green and eco-friendly synthesis, easy accessibility, sustainable strategy, and improved battery performance, including capacity, cycling property, and stability/durability. This tutorial review focusing on biomass-derived carbons and their composites in the application of LIB anodes will act as a strategic guide to build a close connection between renewable materials and electrochemical energy storage devices. Also, this review provides a critical analysis and comparison of biomass-derived carbons and their composites for LIB anodes, coupled with an important insight into the remaining challenges and future directions in the field.

Hierarchical nanostructured carbons with meso-macroporosity: design, characterization, and applications.

Nanostructured porous carbon materials have diverse applications including sorbents, catalyst supports for fuel cells, electrode materials for capacitors, and hydrogen storage systems. When these materials have hierarchical porosity, interconnected pores of different dimensions, their potential application is increased. Hierarchical nanostructured carbons (HNCs) that contain 3D-interconnected macroporous/mesoporous and mesoporous/microporous structures have enhanced properties compared with single-sized porous carbon materials, because they have improved mass transport through the macropores/mesopores and enhanced selectivity and increased specific surface area on the level of fine pore systems through mesopores/micropores. The HNCs with macro/mesoporosity are of particular interest because chemists can tailor specific applications through controllable synthesis of HNCs with designed nanostructures. An efficient and commonly used technique for creating HNCs is "nanocasting", a technique that first involves the creation of a sacrificial silica template with hierarchical porous nanostructure and then the impregnation of the silica template with an appropriate carbon source. This is followed by carbonization of the filled carbon precursor, and subsequent removal of the silica template. The resulting HNC is an inverse replica of its parent hierarchical nanostructured silica (HNS). Through such nanocasting, scientists can create different HNC frameworks with tailored pore structures and narrow pore size distribution. Generally, HNSs with specific structure and 3D-interconnected porosity are needed to fabricate HNCs using the nanocasting strategy. However, how can we fabricate a HNS framework with tailored structure and hierarchical porosity of meso-macropores? This Account reports on our recent work in the development of novel HNCs and their interesting applications. We have explored a series of strategies to address the challenges in synthesis of HNSs and HNCs. Through careful control of experimental parameters, we found we could readily create new HNSs and HNCs with tailored structure and hierarchical porosity. In this Account, we describe the applications of the HNCs in low-temperature fuel cells, in Li ion batteries, in quantum-dot-sensitized solar cells (QDSSCs) and as hydrogen storage materials. Fuel cell and QDSSC polarization performance data reveal that both the ordered HNC and spherical HNC with uniform macro- and mesoporosity demonstrate superior catalyst support effect and considerably enhanced photovoltaic performance due to their incredible structural characteristics. For hydrogen and lithium storage applications, primary experimental results show that spherical HNCs with uniform macroporous core/mesoporous shell and ordered HNC are highly beneficial in terms of a high hydrogen (or Li) uptake, good rate capability and excellent cycling retainability. These data suggest that the innovative HNCs with tailored nanostructure may find promising applications in the rapid and efficient storage of hydrogen (or Li).

Recent progress in electrode materials for micro-supercapacitors.

Micro-supercapacitors (MSCs) stand out in the field of micro energy storage devices due to their high power density, long cycle life, and environmental friendliness. The key to improving the electrochemical performance of MSCs is the selection of appropriate electrode materials. To date, both the composition and structure of electrode materials in MSCs have become a hot research topic, and it is urgent to compose a review to highlight the most important research achievements, major challenges, opportunities, and encouraging perspectives in this field. In this review, research background of MSCs is first reviewed followed by their working principles, structural classifications, and physiochemical and electrochemical characterization techniques. Next, various materials and preparation methods are summarized, and the relationship between the MSC performance and structure and composition of materials are discussed in depth. Finally, this review provides a comprehensive suggestion on accelerating the development of electrode materials to facilitate the commercialization of MSCs.

Morphology-dependent Li storage performance of ordered mesoporous carbon as anode material.

Rod-shaped ordered mesoporous carbons (OMCs) with different lengths, prepared by replication method using the corresponding size-tunable SBA-15 silicas with the same rodlike morphology as templates, are explored as anode material for Li-ion battery. All of the as-synthesized OMCs exhibit much higher Li storage capacity and better cyclability along with comparable rate capability as compared with commercial graphite. Particularly, the OMC-3 with the shortest length demonstrates the highest reversible discharge capacity of 1012 mAh g(-1) at 100 mA g(-1) and better cyclability with 86.6% retention of initial capacity after 100 cycles. Although the Coulombic efficiencies of all the OMCs are relatively low at the beginning, they improve promptly and after 10 cycles reach the level comparable to commercial graphite. Based on their specific capacity, cycle efficiency, and rate capability, the OMC-3 outperforms considerably its carbon peers, OMC-1 and OMC-2 with longer length. This behavior is mainly attributed to higher specific surface area, which provides more active sites for Li adsorption and storage along with the larger mesopore volume and shorter mesopore channels, which facilitate fast Li ion diffusion and electrolyte transport. The enhancement in reversible Li storage performance with decrease in the channel length is also supported by low solid electrolyte interphase resistance, contact resistance, and Warburg impedance in electrochemical impedance spectroscopy.

Water Management Capacity of Metal Foam Flow Field for PEMFC under Flooding Situation.

Porous metal foam with complex opening geometry has been used as a flow field to enhance the distribution of reactant gas and the removal of water in polymer electrolyte membrane fuel cells. In this study, the water management capacity of a metal foam flow field is experimentally investigated by polarization curve tests and electrochemical impedance spectroscopy measurements. Additionally, the dynamic behavior of water at the cathode and anode under various flooding situations is examined. It is found that obvious flooding phenomena are observed after water addition both into the anode and cathode, which are alleviated during a constant-potential test at 0.6 V. Greater abilities of anti-flooding and mass transfer and higher current densities are found as the same amount of water is added at the anode. No diffusion loop is depicted in the impedance plots although a 58.3% flow volume is occupied by water. The maximum current density of 1.0 A cm-2 and the lowest Rct around 17 mΩ cm2 are obtained at the optimum state after 40 and 50 min of operation as 2.0 and 2.5 g of water are added, respectively. The porous metal pores store a certain amount of water to humidify the membrane and achieve an internal "self-humidification" function.

MOF-Derived Nitrogen-Doped Porous Carbon Polyhedrons/Carbon Nanotubes Nanocomposite for High-Performance Lithium-Sulfur Batteries.

Nanocomposites that combine porous materials and a continuous conductive skeleton as a sulfur host can improve the performance of lithium-sulfur (Li-S) batteries. Herein, carbon nanotubes (CNTs) anchoring small-size (~40 nm) N-doped porous carbon polyhedrons (S-NCPs/CNTs) are designed and synthesized via annealing the precursor of zeolitic imidazolate framework-8 grown in situ on CNTs (ZIF-8/CNTs). In the nanocomposite, the S-NCPs serve as an efficient host for immobilizing polysulfides through physical adsorption and chemical bonding, while the interleaved CNT networks offer an efficient charge transport environment. Moreover, the S-NCP/CNT composite with great features of a large specific surface area, high pore volume, and short electronic/ion diffusion depth not only demonstrates a high trapping capacity for soluble lithium polysulfides but also offers an efficient charge/mass transport environment, and an effective buffering of volume changes during charge and discharge. As a result, the Li-S batteries based on a S/S-NCP/CNT cathode deliver a high initial capacity of 1213.8 mAh g-1 at a current rate of 0.2 C and a substantial capacity of 1114.2 mAh g-1 after 100 cycles, corresponding to a high-capacity retention of 91.7%. This approach provides a practical research direction for the design of MOF-derived carbon materials in the application of high-performance Li-S batteries.

Recent Advances in Porous Carbon Materials as Electrodes for Supercapacitors.

Porous carbon materials have demonstrated exceptional performance in various energy and environment-related applications. Recently, research on supercapacitors has been steadily increasing, and porous carbon materials have emerged as the most significant electrode material for supercapacitors. Nonetheless, the high cost and potential for environmental pollution associated with the preparation process of porous carbon materials remain significant issues. This paper presents an overview of common methods for preparing porous carbon materials, including the carbon-activation method, hard-templating method, soft-templating method, sacrificial-templating method, and self-templating method. Additionally, we also review several emerging methods for the preparation of porous carbon materials, such as copolymer pyrolysis, carbohydrate self-activation, and laser scribing. We then categorise porous carbons based on their pore sizes and the presence or absence of heteroatom doping. Finally, we provide an overview of recent applications of porous carbon materials as electrodes for supercapacitors.

Cost-Effective Fabrication of Modified Palygorskite-Reinforced Rigid Polyurethane Foam Nanocomposites.

Integration of nanoclay minerals into rigid polyurethane foams (RPUFs) is a cost-effective solution to enhance foam's performance via environmental protection technology. In this work, palygorskite/RPUFs nanocomposites (Pal/RPUFNs) with excellent mechanical properties and thermal stability were prepared via a one-step method, using 4,4'-diphenylmethane diisocyanate and polyether polyol as the starting materials, coupled with Pal modified by silane coupling agent KH570. The effects of the modified Pal on the mechanics, morphology, and thermal properties of the nanocomposites were studied systematically. When the content of the modified Pal was 8 wt% of polyether polyol, the elastic modulus and compressive strength of the Pal/RPUFNs were increased by ca. 131% and 97%, respectively. The scanning electron microscopy images indicated that the addition of the modified Pal significantly decreased the cell diameter of the Pal/RPUFNs. The results of thermogravimetric and derivative thermogravimetry analyses revealed that the addition of the modified Pal increased the thermal weight loss central temperature of the Pal/RPUFNs, showing better thermal stability in comparison with the pure RPUFs. A self-made evaluation device was used to estimate the thermal insulation ability of the Pal/RPUFNs. It was found that the small cell size and uniform cellular structure were keys to improving the thermal insulation performance of the RPUFs. The prepared Pal/RPUFNs are expected to have great potential in the field of building insulation.

Stainless Steel-Supported Amorphous Nickel Phosphide/Nickel as an Electrocatalyst for Hydrogen Evolution Reaction.

Recently, nickel phosphides (Ni-P) in an amorphous state have emerged as potential catalysts with high intrinsic activity and excellent electrochemical stability for hydrogen evolution reactions (HER). However, it still lacks a good strategy to prepare amorphous Ni-P with rich surface defects or structural boundaries, and it is also hard to construct a porous Ni-P layer with favorable electron transport and gas-liquid transport. Herein, an integrated porous electrode consisting of amorphous Ni-P and a Ni interlayer was successfully constructed on a 316L stainless steel felt (denoted as Ni-P/Ni-316L). The results demonstrated that the pH of the plating solution significantly affected the grain size, pore size and distribution, and roughness of the cell-like particle surface of the amorphous Ni-P layer. The Ni-P/Ni-316L prepared at pH = 3 presented the richest surface defects or structural boundaries as well as porous structure. As expected, the as-developed Ni-P/Ni-316L demonstrated the best kinetics, with η10 of 73 mV and a Tafel slope of ca. 52 mV dec-1 for the HER among all the electrocatalysts prepared at various pH values. Furthermore, the Ni-P/Ni-316L exhibited comparable electrocatalytic HER performance and better durability than the commercial Pt (20 wt%)/C in a real water electrolysis cell, indicating that the non-precious metal-based Ni-P/Ni-316L is promising for large-scale processing and practical use.

Robust Porous TiN Layer for Improved Oxygen Evolution Reaction Performance.

The poor reversibility and slow reaction kinetics of catalytic materials seriously hinder the industrialization process of proton exchange membrane (PEM) water electrolysis. It is necessary to develop high-performance and low-cost electrocatalysts to reduce the loss of reaction kinetics. In this study, a novel catalyst support featured with porous surface structure and good electronic conductivity was successfully prepared by surface modification via a thermal nitriding method under ammonia atmosphere. The morphology and composition characterization-confirmed that a TiN layer with granular porous structure and internal pore-like defects was established on the Ti sheet. Meanwhile, the conductivity measurements showed that the in-plane electronic conductivity of the as-developed material increased significantly to 120.8 S cm−1. After IrOx was loaded on the prepared TiN-Ti support, better dispersion of the active phase IrOx, lower ohmic resistance, and faster charge transfer resistance were verified, and accordingly, more accessible catalytic active sites on the catalytic interface were developed as revealed by the electrochemical characterizations. Compared with the IrOx/Ti, the as-obtained IrOx/TiN-Ti catalyst demonstrated remarkable electrocatalytic activity (η10 mA cm−2 = 302 mV) and superior stability (overpotential degradation rate: 0.067 mV h−1) probably due to the enhanced mass adsorption and transport, good dispersion of the supported active phase IrOx, increased electronic conductivity and improved corrosion resistance provided by the TiN-Ti support.

No Evidence of Benefits of Host Nano-Carbon Materials for Practical Lithium Anode-Free Cells.

Nano-carbon-based materials are widely reported as lithium host materials in lithium metal batteries (LMBs); however, researchers report contradictory claims as to where the lithium plating occurs. Herein, the use of pure hollow core-carbon spheres coated on Cu (PHCCSs@Cu) to study the lithium deposition behavior with respect to this type of structure in lithium anode-free cells is described. It is demonstrated that the lithium showed some initial and limited intercalation into the PHCCSs and then plated on the external carbon walls and the top surface of the carbon coating during the charging process. The unfavorable deposition of lithium inside the PHCCSs is discussed from the viewpoint of lithium-ion transport and lithium nucleation. The application potential of PHCCSs and the data from these LMB studies are also discussed.

Rational Design of Multimodal Porous Carbon for the Interfacial Microporous Layer of Fuel Cell Oxygen Electrodes.

Accumulation of water at the interface of the cathode catalyst layer (CCL) and the diffusion media is a major cause of performance loss in H2/air fuel cells. Proper engineering of the interface by the use of advanced materials and preparation methods can effectively reduce the extent of this loss by improving the transport of water and gas across this interface. Herein, we present detailed modeling results of water and gas transport across this interface for in-house synthesized carbon material with multiple levels of porosity and by considering the interfacial properties of the carbon material and the microporous layer (MPL). The oxygen reduction reaction and the counter-flow transport of oxygen and water within the CCL and MPL pores were modeled considering a partially flooded interface. Well-characterized multimodal porous carbon was chosen as a candidate material for this study, and the effects of all the various levels of porosity in the MPL, wettability, permeability, and the quality of contact between the MPL and CCL on the transport phenomena of fluids were investigated. This study provides new insights into the balance of opposing transport phenomena on the local and overall performance of the catalyst layer and rationalizes the design parameters for an MPL material based on both the material and interfacial properties.