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Photo-accelerated rechargeable batteries play a crucial role in fully utilizing solar energy, but it is still a challenge to fabricate dual-functional photoelectrodes with simultaneous high solar energy harvesting and storage. This work reports an innovative photo-accelerated zinc-ion battery (PAZIB) featuring a photocathode with a SnO2@MnO2 heterojunction. The design ingeniously combines the excellent electronic conductivity of SnO2 with the high energy storage and light absorption capacities of MnO2. The capacity of the SnO2@MnO2-based PAZIB is ≈598 mAh g-1 with a high photo-conversion efficiency of 1.2% under illumination at 0.1 A g-1, which is superior to that of most reported MnO2-based ZIB. The boosting performance is attributed to the synergistic effect of enhanced photogenerated carrier separation efficiency, improved conductivity, and promoted charge transfer by the SnO2@MnO2 heterojunction, which is confirmed by systematic experiments and theoretical simulations. This work provides valuable insights into the development of dual-function photocathodes for effective solar energy utilization.

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Na2Ti3/2Mn1/2(PO4)3 nanodots uniformly planted in a carbon matrix are reported for the first time as a promising low-cost anode for aqueous sodium-ion batteries, showing ultrafast Na-intercalation chemistry with stable capacities of 78.8 mA h g-1 at 0.5C and 65.1 mA h g-1 at 10C, and a capacity retention of 93% after 200 cycles.

RESUMEN

Sodium vanadium fluorophosphate (Na3(VO)2(PO4)2F, denoted as NVPF) has attracted particular interests as cathode for high-energy sodium-ion batteries (SIBs) owing to the high working potential, high specific capacity, and robust structural framework. However, it is challenged by the low electron conductivity and lack of available facile synthesis method. Herein, an environmentally benign, cost-effective synthesis route is reported to produce NVPF nanoparticles encapsulated in conductive graphene network (NVPF/C), involving low-temperature synthesis of NVPF nanoparticles in absolute aqueous solvents and subsequent construction of conductive network through thermally induced transformation of graphene-oxide nanosheets. The resultant product is structurally and electrochemically investigated by combining X-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscope, transition electron microscope, and electrochemical analysis. Experimental results show that the optimized NVPF/C product possesses a three-dimensional graphene-encapsulation nanostructure composed of ∼100 nm NVPF nanoparticles and ∼4 nm carbon-coating layer. The unique hierarchical structure enables it cycling with excellent electrochemical performance in terms of a high reversible capacity (116.4 mA h g-1 at 0.2 C), excellent high-rate capability (87.4 mA h g-1 at 10 C) and long-term lifetime (82.1% capacity retention after 1200 cycles). It is indicated that the facile synthesis route can achieve high-performance NVPF/C material for SIBs.

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Aqueous sodium-ion batteries (SIBs) represent a class of green electrochemical technology for large-scale storage of sustainable energies such as wind power and solar radiation, owing to their low cost, environmental friendliness, and reliable safety. However, there is still lack of available anode materials for aqueous SIBs. Herein, nanocrystal-assembled porous Na3 MgTi(PO4 )3 aggregates are reported as novel anode material for aqueous SIBs. The crystal structure, morphological features, and electrochemical properties have been analyzed with X-ray diffraction, scanning electron microscopy, transition electron microscopy, cyclic voltammetry, and charge/discharge measurements. As revealed, the material possesses a porous nanostructure composed of 5 nm nanocrystals and mesoporous channels. During Na-insertion/extraction, it undergoes a one-step single-phase reaction mechanism through reversible electrochemistry of the Ti4+ /Ti3+ redox couple, showing a rechargeable capacity of 54 mAh g-1 and an average working potential of -0.63 V (vs. Ag/AgCl) at 0.2 C. More importantly, good rate capacity (33 mAh g-1 at 4 C) and excellent cycling performance (94.2 % capacity retention after 100 cycles at 0.5 C) are achieved due to the unique porous nanostructure and robust compositional framework. The finding in this work would create new opportunities for design of low-cost, long-cycling aqueous SIBs.

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Na3(VO(0.5))2(PO4)2F2 nanoparticles embedded in porous graphene have been reported as a superior high-rate cathode material for sodium-ion batteries, exhibiting an excellent electrochemical performance with a high reversible capacity of 100 mA h g(-1) at 1 C, 77 mA h g(-1) at 50 C, and a capacity retention of 73% after 1000 cycles at 50 C. In particular, a significant contribution of the pseudocapacitive effect to the Na-storage capacity has been found for the first time.

RESUMEN

Sodium-ion batteries (SIBs) receive significant attention for electrochemical energy storage and conversion owing to their wide availability and the low cost of Na resources. However, SIBs face challenges of low specific energy, short cycling life, and insufficient specific power, owing to the heavy mass and large radius of Na(+) ions. As an important component of SIBs, cathode materials have a significant effect on the SIB electrochemical performance. The most recent advances and prospects of inorganic and organic cathode materials are summarized here. Among current cathode materials, layered transition-metal oxides achieve high specific energies around 600 mW h g(-1) owing to their high specific capacities of 180-220 mA h g(-1) and their moderate operating potentials of 2.7-3.2 V (vs Na(+) /Na). Porous Na3 V2 (PO4 )3 /C nanomaterials exhibit excellent cycling performance with almost 100% retention over 1000 cycles owing to their robust structural framework. Recent emerging cathode materials, such as amorphous NaFePO4 and pteridine derivatives show interesting electrochemical properties and attractive prospects for application in SIBs. Future work should focus on strategies to enhance the overall performance of cathode materials in terms of specific energy, cycling life, and rate capability with cationic doping, anionic substitution, morphology fabrication, and electrolyte matching.

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A novel electrode, carbon felt-supported nano-molybdenum carbide (Mo2C)/carbon nanotubes (CNTs) composite, was developed as platinum-free anode of high performance microbial fuel cell (MFC). The Mo2C/CNTs composite was synthesized by using the microwave-assisted method with Mo(CO)6 as a single source precursor and characterized by using X-ray diffraction and transmission electron microscopy. The activity of the composite as anode electrocatalyst of MFC based on Escherichia coli (E. coli) was investigated with cyclic voltammetry, chronoamperometry, and cell discharge test. It is found that the carbon felt electrode with 16.7 wt% Mo Mo2C/CNTs composite exhibits a comparable electrocatalytic activity to that with 20 wt% platinum as anode electrocatalyst. The superior performance of the developed platinum-free electrode can be ascribed to the bifunctional electrocatalysis of Mo2C/CNTs for the conversion of organic substrates into electricity through bacteria. The composite facilitates the formation of biofilm, which is necessary for the electron transfer via c-type cytochrome and nanowires. On the other hand, the composite exhibits the electrocatalytic activity towards the oxidation of hydrogen, which is the common metabolite of E. coli.

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RESUMEN

A composite, polyaniline (PANI)/mesoporous tungsten trioxide (m-WO(3)), was developed as a platinum-free and biocompatible anodic electrocatalyst of microbial fuel cells (MFCs). The m-WO(3) was synthesized by a replicating route and PANI was loaded on the m-WO(3) through the chemical oxidation of aniline. The composite was characterized by using X-ray diffraction, Fourier transform infrared spectrum, field emission scanning electron microscopy, and transmission electron microscopy. The activity of the composite as the anode electrocatalyst of MFC based on Escherichia coli (E. coli) was investigated with cyclic voltammetry, chronoamperometry, and cell discharge test. It is found that the composite exhibits a unique electrocatalytic activity. The maximum power density is 0.98 W m(-2) for MFC using the composite electrocatalyst, while only 0.76 W m(-2) and 0.48 W m(-2) for the MFC using individual m-WO(3) and PANI electrocatalyst, respectively. The improved electrocatalytic activity of the composite can be ascribed to the combination of m-WO(3) and PANI. The m-WO(3) has good biocompatibility and PANI has good electrical conductivity. Most importantly, the combination of m-WO(3) and PANI improves the electrochemical activity of PANI for proton insertion and de-insertion.

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