Universal Synthesis of Half-Metallic Diatomic Catalysts for Efficient Oxygen Reduction Electrocatalysis.

Developing efficient and low-cost noble-free metal electrocatalysts is an urgent requirement. Herein, a one-step, solid-state template-assisted method for fabricating isolated half-metallic diatomic M, Zn─N─C (M═Fe, Co, and Ni) catalysts is reported. In particular, the fabricated Fe, Zn─N─C structure exhibits superior oxygen reduction reaction capabilities with a half-wave potential of 0.867 V versus RHE. The Mossbauer spectra reveal that the Fe, Zn─N─C half-metallic diatomic catalyst has a large proportion of the D2 site (ferrous iron with a medium spin state). Density functional theory (DFT) reveals that in Fe, Zn─N─C structures, the zinc sites play a unique role in accelerating the protonation process of O2 in ORR. In assembled zinc-air batteries, a maximum power density of 138 mW cm-2 and a capacity of 748 mAh g zn-1 can be obtained. This work fabricates a series of efficient M, Zn─N─C diatomic electrocatalysts, and the developed solid-state reaction method can hopefully apply in other energy conversion and storage fields.

Solution plasma synthesis of Pt-decorated Bi12O17Cl2 photocatalysts for efficient upcycling of plastics.

Photocatalytic upcycling of plastic waste is a promising approach to relieving pressure caused by solid waste, but the rational design of novel efficient photocatalysts remains a challenge. Herein, we utilize subnano-sized platinum (Pt)-based photocatalysts for plastic upcycling. A solution plasma strategy is developed to fabricate Pt-decorated Bi12O17Cl2 (SP-BOC). The Pt in an oxidant state and oxygen vacancies optimize the electronic structure for fast charge transfer. As a result, SP-BOC displays high performance for upcycling polyvinyl chloride (PVC) and polylactic acid (PLA) into acetic acid and formic acid, with yield rate and selectivity of 6.07 mg g-1cat. h-1 and 94 %, and 47.43 mg g-1cat. h-1 and 55.1 %, respectively. In addition, the dichlorination efficiency of PVC reaches 78.1 % within 10 h reaction, effectively reducing the environmental hazards associated with PVC waste disposal treatments. This research provides insight into the effective conversion of plastics into high-value chemicals, contributing to the reduction of carbon and toxic emissions in a practical and meaningful way, and offering a useful way for solving challenges of waste management and environmental sustainability.

High entropy alloy nanoparticles encapsulated in graphitised hollow carbon tubes for oxygen reduction electrocatalysis.

High entropy alloys (HEAs) with a tunable alloy composition and fascinating synergetic effects between various metals have attracted significant attention in the field of electrocatalysis, but their potential is limited by inefficient and unscalable fabrication methodologies. This work proposes a novel solid-state thermal reaction method to synthesise HEA nanoparticles encapsulated in an N-doped graphitised hollow carbon tube. This facile method is simple and efficient and involves no use of organic solvents during the fabrication process. The synthesized HEA nanoparticles are confined by the graphitised hollow carbon tube, which is possibly beneficial for preventing the aggregation of alloy particles during the oxygen reduction reaction (ORR). In a 0.1 M KOH solution, the HEA catalyst FeCoNiMnCu-1000(1 : 1) exhibits an onset and half-wave potential of 0.92 V and 0.78 V (vs. RHE), respectively. We assembled a Zn-Air battery with FeCoNiMnCu-1000 as a catalyst for the air electrode, and a power density of 81 mW cm-2 and a long-term durability of >200 h were achieved, which is comparable to the performance of the state-of-the-art catalyst Pt/C-RuO2. This work herein offers a scalable and green method for synthesising multinary transition metal-based HEAs and highlights the potential of HEA nanoparticles as electrocatalysts for energy storage and conversion.

Janus Hollow Nanofiber with Bifunctional Oxygen Electrocatalyst for Rechargeable Zn-Air Battery.

Zn-air battery technologies have received increasing attention, while the application is hindered by the sluggish kinetics of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). In order to explore an efficient method to fabricate a high-performance electrocatalyst via modification of advanced nanostructure, a coaxial electrospinning method with in-situ synthesis and subsequent carbonization to construct 3D flexible Janus-like electrocatalysts is developed. The resulting Janus nanofibers have a unique core-shell hollow fiber structure, where NiFe alloy electrocatalysts supported by N-doped carbon nanobelt are located on the inner wall of the carbon layer, and leaf-like Co-N nanosheets are anchored on the outer wall of the carbon layer. As a result, the electrocatalyst exhibits excellent bifunctional catalytic performance for ORR and OER, demonstrating the small potential gap value of 0.73 V between the ORR half-wave potential and the OER potential at 10 mA cm-2 , which is even comparable to the mixed commercial noble catalyst with 20% Pt/C and RuO2 . The rechargeable Zn-air battery is constructed and displays a large open-circuit voltage of 1.44 V, high power density (130 mW cm-2 ) and energy density (874 Wh kg-1 ). This study provides a concept to synthesize and construct high performance bifunctional electrocatalysts.

Enhanced Cr(VI) reduction in biocathode microbial electrolysis cell using Fenton-derived ferric sludge.

Hexavalent chromium (Cr(VI)) is one of the major concerns for water environment and human health due to its high toxicicity, while ferric sludge produced from Fenton processes is also a tough nut to crack. In this study, the synergetic impact of ferric sludge derived from the Fenton process on the bioreduction of Cr(VI) in biocathode microbial electrolysis cell was investigated for the first time. As a result, Cr(VI) reduction efficiency at biocathode increased by 1.1-2.6 times with 50 mg/L ferric sludge under different operation conditions. Besides, the Cr(VI) reduction enhancement decreased with the increase of pH and initial Cr(VI) concentration or increased with the increase of ferric sludge dosage. Correspondingly, relatively higher power density (1.027 W/m3 with 100 mg/L ferric sludge while 0.827 W/m3 for control) and lower activation energy and resistance were also observed. Besides, the presence of ferric sludge increased biomass protein (1.7 times higher with 100 mg/L ferric sludge) and cytochrome c (1.4 times higher with 100 mg/L ferric sludge). The evolution of microbial community structure for a higher abundance of Cr(VI) and Fe(III)-reducing microorganisms were exhibited, implying the enhancement of Cr(VI) reduction was due to the formation of Fe(II) from the reduction of ferric sludge. These findings provide insights and theoretical support for developing a viable biotechnology platform to realize waste treatment using waste.

Random Occupation of Multimetal Sites in Transition Metal-Organic Frameworks for Boosting the Oxygen Evolution Reaction.

Developing robust oxygen evolution reaction (OER) electrocatalysts with excellent performance is essential for the conversion of renewable electricity to clean fuel. Herein, we present a facile concept for the synthesis of efficient high-entropy metal-organic frameworks (HEMOFs) as electrocatalysts in a one-step solvothermal synthesis. This strategy allows control of the microstructure and corresponding lattice distortion by tuning the metal ion composition. As a result, the OER activity was improved by optimizing the coordination environment of the metal catalytic center. The optimized Co-rich HEMOFs exhibited a low overpotential of 310 mV at a current density of 10 mA cm-2 , better than a RuO2 catalyst tested under the same conditions. The finding of lattice distortion of the HEMOFs provides a new strategy for developing high-performance electrocatalysts for energy conversion.

Cost-efficient microbial electrosynthesis of hydrogen peroxide on a facile-prepared floating electrode by entrapping oxygen.

Microbial electrosynthesis of hydrogen peroxide is receiving growing interest for a green substitute for anthraquinone process.However, poor oxygen transmission of electrode remains an obstacle to enhance H2O2 production rate without aeration. Here, a superhydrophobic natural air diffusion floating electrode (NADFE), which naturally and efficiently entraps O2 in the air, was proposed for the first time to improve microbial electrosynthesis of H2O2. Furthermore, a one-step calcined electrode preparation method was developed to reduce energy consumption further. In the microbial electrolysis cell with the NADFE, a high H2O2 production rate of 39 mg/L/h and current efficiency of 86% were achieved without aeration. The production rate of H2O2 was 2.2 times that of a gas diffusion electrode. Importantly, the energy consumption was 34.3 times lower than an electrochemical system. Therefore, the high H2O2 production rate and current efficiency, and low energy consumption of the process provide a superior alternative for environmental remediation.

High-performance supercapacitors based on hierarchically porous carbons with a three-dimensional conductive network structure.

Clews of polymer nanobelts (CsPNBs) have the advantages of inexpensive raw materials, simple synthesis and large output. Novel clews of carbon nanobelts (CsCNBs) have been successfully prepared by carbonizing CsPNBs and by KOH activation subsequently. From the optimized process, CsCNBs*4, with a specific surface area of 2291 m2 g-1 and a pore volume of up to 1.29 cm3 g-1, has been obtained. Fundamentally, the CsCNBs possess a three-dimensional conductive network structure, a hierarchically porous framework, and excellent hydrophilicity, which enable fast ion diffusion through channels and a large enough ion adsorption/desorption surface to improve electrochemical performance of supercapacitors. The product exhibits a high specific capacitance of 327.5 F g-1 at a current density of 0.5 A g-1 in a three-electrode system. The results also reveal a high-rate capacitance (72.2% capacitance retention at 500 mV s-1) and stable cycling lifetime (95% of initial capacitance after 15 000 cycles). Moreover, CsCNBs*4 provides a high energy density of 29.8 W h kg-1 at a power density of 345.4 W kg-1 in 1 M tetraethylammonium tetrafluoroborate/acetonitrile (TEABF4/AN) electrolyte. These inspiring results imply that this carbon material with a three-dimensional conductive network structure possesses excellent potential for energy storage.

Evolving mechanism of organotemplate-free hierarchical FAU zeolites with house-of-card-like structures.

Hierarchical FAU zeolites with house-of-card-like (HCL) structures were synthesized through a one-pot organotemplate-free route in the Na2O-Al2O3-SiO2-H2O system. The structure details and formation mechanism of HCL zeolites were determined by the combination of electron crystallography and synthesis chemistry. The results revealed that the unique HCL morphology was attributed to large solution viscosity, and the evolution process obeyed a skeleton crystal growth model due to the limited vortexing effect, which was different from those of the HCL zeolites obtained using organic templates.

A Universal Strategy To Prepare Sulfur-Containing Polymer Composites with Desired Morphologies for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are probably the most promising candidates for the next-generation batteries owing to their high energy density. However, Li-S batteries face severe technical problems where the dissolution of intermediate polysulfides is the biggest problem because it leads to the degradation of the cathode and the lithium anode, and finally the fast capacity decay. Compared with the composites of elemental sulfur and other matrices, sulfur-containing polymers (SCPs) have strong chemical bonds to sulfur and therefore show low dissolution of polysulfides. Unfortunately, most SCPs have very low electron conductivity and their morphologies can hardly be controlled, which undoubtedly depress the battery performances of SCPs. To overcome these two weaknesses of SCPs, a new strategy was developed for preparing SCP composites with enhanced conductivity and desired morphologies. With this strategy, macroporous SCP composites were successfully prepared from hierarchical porous carbon. The composites displayed discharge/charge capacities up to 1218/1139, 949/922, and 796/785 mA h g-1 at the current rates of 5, 10, and 15 C, respectively. Considering the universality of this strategy and the numerous morphologies of carbon materials, this strategy opens many opportunities for making carbon/SCP composites with novel morphologies.

Nitrogen-doped graphitic hierarchically porous carbon nanofibers obtained via bimetallic-coordination organic framework modification and their application in supercapacitors.

Herein, N-doped graphitic hierarchically porous carbon nanofibers (NGHPCF) were prepared by electrospinning the composite of bimetallic-coordination metal-organic frameworks and polyacrylonitrile, followed by a pyrolysis and acid wash process. Control over the N content, specific surface area, and degree of graphitization of NGHPCF materials has been realized by adjusting the Co/Zn metal coordination content as well as the pyrolysis temperature. The obtained NGHPCF with a high specific surface area (623 m2 g-1) and nitrogen content (13.83 wt%) exhibit a high capacitance of 326 F g-1 at 0.5 A g-1. In addition, the capacitance of 170 F g-1 is still maintained at a high current density (40 A g-1); this indicates a high capacitance retention capability. Furthermore, a superb energy density (9.61 W h kg-1) is obtained with a high power density (62.4 W kg-1) using an organic electrolyte. These results fully illustrate that the prepared NGHPCF binder-free electrodes are promising candidates for high-performance supercapacitors.

Facile Synthesis of Nitrogen and Oxygen Co-Doped Clews of Carbon Nanobelts for Supercapacitors with Excellent Rate Performance.

Facile synthesis of carbon materials with high heteroatom content, large specific surface area (SSA) and hierarchical porous structure is critical for energy storage applications. In this study, nitrogen and oxygen co-doped clews of carbon nanobelts (NCNBs) with hierarchical porous structures are successfully prepared by a carbonization and subsequent activation by using ladder polymer of hydroquinone and formaldehyde (LPHF) as the precursor and ammonia as the activating agent. The hierarchical porous structures and ultra-high SSA (up to 2994 m² g−1) can effectively facilitate the exchange and transportation of electrons and ions. Moreover, suitable heteroatom content is believed to modify the wettability of the carbon material. The as-prepared activated NCNBs-60 (the NCNBs activated by ammonia at 950 °C for 60 min) possess a high capacitance of 282 F g−1 at the current density of 0.25 A g−1, NCNBs-45 (the NCNBs are activated by ammonia at 950 °C for 45 min) and show an excellent capacity retention of 50.2% when the current density increase from 0.25 to 150 A g−1. Moreover, the NCNBs-45 electrode exhibits superior electrochemical stability with 96.2% capacity retention after 10,000 cycles at 5.0 A g−1. The newly prepared NCNBs thus show great potential in the field of energy storage.

Facile synthesis of high-surface-area nanoporous carbon from biomass resources and its application in supercapacitors.

It is critical for nanoporous carbons to have a large surface area, and low cost and be readily available for challenging energy and environmental issues. The pursuit of all three characteristics, particularly large surface area, is a formidable challenge because traditional methods to produce porous carbon materials with a high surface area are complicated and expensive, frequently resulting in pollution (commonly from the activation process). Here we report a facile method to synthesize nanoporous carbon materials with a high surface area of up to 1234 m2 g-1 and an average pore diameter of 0.88 nm through a simple carbonization procedure with carefully selected carbon precursors (biomass material) and carbonization conditions. It is the high surface area that leads to a high capacitance (up to 213 F g-1 at 0.1 A g-1) and a stable cycle performance (6.6% loss over 12 000 cycles) as shown in a three-electrode cell. Furthermore, the high capacitance (107 F g-1 at 0.1 A g-1) can be obtained in a supercapacitor device. This facile approach may open a door for the preparation of high surface area porous carbons for energy storage.

Facile Synthesis of Ultrahigh-Surface-Area Hollow Carbon Nanospheres and their Application in Lithium-Sulfur Batteries.

Hollow carbon nanospheres (HCNs) with specific surface areas up to 2949 m2 g-1 and pore volume up to 2.9 cm3 g-1 were successfully synthesized from polyaniline-co-polypyrrole hollow nanospheres by carbonization and CO2 activation. The cavity diameter and wall thickness of HCNs can be easily controlled by activation time. Owing to their large inner cavity and enclosed structure, HCNs are desirable carriers for encapsulating sulfur. To better understand the effects of pore characteristics and sulfur contents on the performances of lithium-sulfur batteries, three composites of HCNs and sulfur are prepared and studied in detail. The composites of HCNs with moderate specific surface areas and suitable sulfur content present a better performance. The first discharge capacity of this composite reaches 1401 mAh g-1 at 0.2 C. Even after 200 cycles, the discharge capacity remains at 626 mAh g-1 .