Despite their high theoretical specific capacity (1675 mA h g−1), the practical application of Li–S batteries remains limited because the capacity rapidly degrades through severe dissolution of ...lithium polysulfide and the rate capability is low because of the low electronic conductivity of sulfur. This paper describes novel hierarchical yolk–shell microspheres comprising 1D bamboo‐like N‐doped carbon nanotubes (CNTs) encapsulating Co nanoparticles (Co@BNCNTs YS microspheres) as efficient cathode hosts for Li–S batteries. The microspheres are produced via a two‐step process that involves generation of the microsphere followed by N‐doped CNTs growth. The hierarchical yolk–shell structure enables efficient sulfur loading and mitigates the dissolution of lithium polysulfides, and metallic Co and N doping improves the chemical affinity of the microspheres with sulfur species. Accordingly, a Co@BNCNTs YS microsphere‐based cathode containing 64 wt% sulfur exhibits a high discharge capacity of 700.2 mA h g−1 after 400 cycles at a current density of 1 C (based on the mass of sulfur); this corresponds to a good capacity retention of 76% and capacity fading rate of 0.06% per cycle with an excellent rate performance (752 mA h g−1 at 2.0 C) when applied as cathode hosts for Li–S batteries.
Hierarchical yolk–shell microspheres comprising 1D bamboo‐like N‐doped carbon nanotubes (CNTs) encapsulating Co nanocrystals are first introduced as efficient cathode hosts for Li–S batteries. The synergetic effect of the presence of the N‐doped CNTs with Co nanocrystals and the hierarchical structure of yolk‐shell microspheres is responsible for the superior performances as the cathode hosts for Li–S batteries.
A novel anode material for sodium‐ion batteries consisting of 3D graphene microspheres divided into several tens of uniform nanospheres coated with few‐layered MoS2 by a one‐pot spray pyrolysis ...process is prepared. The first discharge/charge capacities of the composite microspheres are 797 and 573 mA h g−1 at a current density of 0.2 A g−1. The 600th discharge capacity of the composite microspheres at a current density of 1.5 A g−1 is 322 mA h g−1. The Coulombic efficiency during the 600 cycles is as high as 99.98%. The outstanding Na ion storage properties of the 3D MoS2–graphene composite microspheres may be attributed to the reduced stacking of the MoS2 layers and to the 3D structure of the porous graphene microspheres. The reduced stacking of the MoS2 layers relaxes the strain and lowers the barrier for Na+ insertion. The empty nanospheres of the graphene offer voids for volume expansion and pathways for fast electron transfer during repeated cycling.
3D MoS2–graphene composite microspheres consisting of multiple nanospheres are prepared by a one‐pot spray pyrolysis process with high scale‐up potential. The 3D MoS2–graphene composite microspheres show high reversible capacity and long cycle stability as anode materials for sodium‐ion batteries. The facile and continuous synthesis of 3D graphene‐based composite microspheres could be applied to the potential materials for various fields including energy storage.
Natural photosynthesis is an effective route for the clean and sustainable conversion of CO2 into high‐energy chemicals. Inspired by the natural process, a tandem photoelectrochemical (PEC) cell with ...an integrated enzyme‐cascade (TPIEC) system was designed, which transfers photogenerated electrons to a multienzyme cascade for the biocatalyzed reduction of CO2 to methanol. A hematite photoanode and a bismuth ferrite photocathode were applied to fabricate the iron oxide based tandem PEC cell for visible‐light‐assisted regeneration of the nicotinamide cofactor (NADH). The cell utilized water as an electron donor and spontaneously regenerated NADH. To complete the TPIEC system, a superior three‐dehydrogenase cascade system was employed in the cathodic part of the PEC cell. Under applied bias, the TPIEC system achieved a high methanol conversion output of 220 μm h−1, 1280 μmol g−1 h−1 using readily available solar energy and water.
In synergy: A tandem photoelectrochemical (PEC) cell with an integrated enzyme cascade has been developed to transfer photogenerated electrons to a multienzyme cascade for the biocatalyzed reduction of CO2 to methanol in high yield. The approach makes use of water as an electron donor, a hematite photoanode and a bismuth ferrite photocathode for the regeneration of NADH with visible light, as well as a three‐dehydrogenase cascade system.
Z‐scheme‐inspired tandem photoelectrochemical (PEC) cells have received attention as a sustainable platform for solar‐driven CO2 reduction. Here, continuously 3D‐structured, electrically conductive ...titanium nitride nanoshells (3D TiN) for biocatalytic CO2‐to‐formate conversion in a bias‐free tandem PEC system are reported. The 3D TiN exhibits a periodically porous network with high porosity (92.1%) and conductivity (6.72 × 104 S m−1), which allows for high enzyme loading and direct electron transfer (DET) to the immobilized enzyme. It is found that the W‐containing formate dehydrogenase from Clostridium ljungdahlii (ClFDH) on the 3D TiN nanoshell is electrically activated through DET for CO2 reduction. At a low overpotential of 40 mV, the 3D TiN‐ClFDH stably converts CO2 to formate at a rate of 0.34 µmol h−1 cm−2 and a faradaic efficiency (FE) of 93.5%. Compared to a flat TiN‐ClFDH, the 3D TiN‐ClFDH shows a 58 times higher formate production rate (1.74 µmol h−1 cm−2) at 240 mV of overpotential. Lastly, a bias‐free biocatalytic tandem PEC cell that converted CO2 to formate at an average rate of 0.78 µmol h−1 and an FE of 77.3% only using solar energy and water is successfully assembled.
A conductive 3D TiN nanoshell electrode is developed for biocatalysis‐coupled photoelectrochemical cells that reduce CO2 through direct electron transfer driven by solar energy without any external bias. The tandem cell structure provides sufficient photovoltage to gain electrons from solar water oxidation, to transport electrons to the 3D biocathode, and to inject electrons into formate dehydrogenase.
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•Biowastes as a resource for producing bioplastics such as polyhydroxyalkanoates (PHAs).•Potential PHAs as nontoxic implants, biocontrol, tissue repair, and drug delivery ...agents.•Strategy for improving soil, delivering biocides, and mulching through PHAs.•Plastic waste management through sustainable technologies.
Plastics are an integral part of most of the daily requirements. Indiscriminate usage and disposal have led to the accumulation of massive quantities of waste. Their non-biodegradable nature makes it increasingly difficult to manage and dispose them. To counter this impending disaster, biodegradable polymers, especially polyhydroxy-alkanoates (PHAs), have been envisaged as potential alternatives. Owing to their unique physicochemical characteristics, PHAs are gaining importance for versatile applications in the agricultural and medical sectors. Applications in the medical sector are more promising because of their commercial viability and sustainability. Despite such potential, their production and commercialization are significant challenges. The major limitations are their poor mechanical strength, production in small quantities, costly feed, and lack of facilities for industrial production. This article provides an overview of the contemporary progress in the field, to attract researchers and stakeholders to further exploit these renewable resources to produce biodegradable plastics on a commercial scale.
A novel type of spherical and porous composites were synthesized to dually benefit from reduced graphene oxide (rGO) and magnetic materials as supports for enzyme immobilization. Three magnetic ...composite particles of Fe3O4 and rGO containing 71% (rGO-Fe3O4-M1), 36% (rGO-Fe3O4-M2), and 18% (rGO-Fe3O4-M3) Fe were prepared using a one-pot spray pyrolysis method and were used for the immobilization of the model enzymes, laccase and horseradish peroxidase (HRP). The rGO-Fe3O4 composite particles prepared by spray pyrolysis process had a regular shape, finite size, and uniform composition. The immobilization of laccase and HRP on rGO-Fe3O4-M1 resulted in 112 and 89.8% immobilization efficiency higher than that of synthesized pure Fe3O4 and rGO particles, respectively. The stability of laccase was improved by approximately 15-fold at 25 °C. Furthermore, rGO-Fe3O4-M1-immobilized laccase exhibited 92.6% of residual activity after 10 cycles of reuse and was 192% more efficient in oxidizing different phenolic compounds than the free enzyme. Therefore, these unique composite particles containing rGO and Fe3O4 may be promising supports for the efficient immobilization of industrially important enzymes with lower acute toxicity toward Vibrio fischeri than commercial pure Fe3O4 particles.
A new mechanism for the transformation of nanostructured metal selenides into uniquely structured metal oxides via the Kirkendall effect, which results from the different diffusion rates of metal and ...Se ions and O2 gas, is proposed. SnSe nanoplates are selected as the first target material and transformed into SnO2 hollow nanoplates by the Kirkendall effect. SnSe‐C composite powder, in which SnSe nanoplates are attached or stuck to amorphous carbon microspheres, transforms into several tens of SnO2 hollow nanoplates by a thermal oxidation process under an air atmosphere. Core–shell‐structured SnSe‐SnSe2@SnO2, SnSe2@SnO2, Se‐SnSe2@SnO2, and Se@SnO2 and yolk–shell‐structured Se@void@SnO2 intermediates are formed step‐by‐step during the oxidation of the SnSe nanoplates. The uniquely structured SnO2 hollow nanoplates have superior cycling and rate performance for Li‐ion storage. Additionally, their discharge capacities at the 2nd and 600th cycles are 598 and 500 mA h g‐1, respectively, and the corresponding capacity retention measured from the 2nd cycle is as high as 84%.
A new mechanism for the transformation of nanostructured metal selenides into uniquely structured metal oxides via the Kirkendall effect is proposed. SnSe nanoplates are selected as the first target material and transformed into SnO2 hollow nanoplates by the Kirkendall effect. The uniquely structured SnO2 hollow nanoplates have superior cycling and rate performance for Li‐ion storage.
•Green and sustainable technologies to circumvent waste management.•Microbial potential to metabolize biowastes into bioactive compounds.•Integrated strategy for recovery of value-adding ...products.•Self-sustaining circular bioeconomy with complete degradation.
Biological wastes generated from food and fruit processing industries, municipal markets, and water treatment facilities are a major cause of concern for Health Departments and Environmentalists around the world. Conventional means of managing these wastes such as transportation, treatment, and disposal, are proving uneconomical. The need is to develop green and sustainable technologies to circumvent this ever-growing and persistent problem. In this article, the potential of diverse microbes to metabolize complex organic rich biowastes into a variety of bioactive compounds with diverse biotechnological applications have been presented. An integrated strategy has been proposed that can be commercially exploited for the recovery of value-adding products ranging from bioactive compounds, chemical building blocks, energy rich chemicals, biopolymers and materials, which results in a self-sustaining circular bioeconomy with nearly zero waste generation and complete degradation.
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•Klebsiella aerogenes yielded 2.82 mol of H2/mol of hexose under dark fermentation.•Biogas derived from DF and anaerobic digestion is integrated to produce methanol.•Methanol ...production by methanotrophs was improved with methane vectors in the feed.•Under the repeated batch mode, 64.6 mmol/L of methanol was produced.
Biowaste-derived sugars or greenhouse gases, such as methane (CH4) and carbon dioxide (CO2), can be used to generate eco-friendly biofuels, such as hydrogen (H2) or methanol. In the present study, enzyme-based rice straw (RS) hydrolysate was used to produce dark-fermentative (DF) biogas (H2 and CO2), which was subsequently integrated with biogas (CH4 and CO2) derived from anaerobic digestion (AD) to generate methanol via methanotrophs. First, DF of RS hydrolysate yielded 2.82 mol of H2/mol of hexose. Second, the integration of biogas derived from DF and AD in the presence of CH4 vectors yielded 13.8 mmol/L of methanol via methanotrophs. Moreover, under the repeated batch mode, 64.6 mmol/L of methanol was produced. This is the first report on the integration of biogas derived from AD and DF of biowaste to produce biomethanol. These findings may facilitate the development of a sustainable biowaste-based circular economy for producing biofuels.
A novel one-dimensional nanohybrid comprised of conductive graphitic carbon (GC)-coated hollow FeSe2 nanospheres decorating reduced graphene oxide (rGO) nanofiber (hollow nanosphere FeSe2@GC-rGO) was ...designed as an efficient anode material for sodium ion batteries and synthesized by introducing the nanoscale Kirkendall effect into the electrospinning method. The electrospun nanofibers transformed into hollow nanosphere FeSe2@GC-rGO hybrid nanofibers through a Fe@GC-rGO intermediate. The discharge capacities of the bare FeSe2 nanofibers, nanorod FeSe2-rGO-amorphous carbon (AC) hybrid nanofibers, and hollow nanosphere FeSe2@GC-rGO hyrbid nanofibers at a current density of 1 A g(-1) for the 150th cycle were 63, 302, and 412 mA h g(-1), respectively, and their corresponding capacity retentions measured from the 2nd cycle were 11, 73, and 82%, respectively. The hollow nanosphere FeSe2@GC-rGO hybrid nanofibers delivered a high discharge capacity of 352 mA h g(-1) even at an extremely high current density of 10 A g(-1). The enhanced electrochemical properties of the hollow nanosphere FeSe2@GC-rGO composite nanofibers arose from the synergetic effects of the FeSe2 hollow morphology and highly conductive rGO matrix.
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