Construction of Ultrathin Nitrogen-Doped Porous Carbon Nanospheres Coated With Polyaniline Nanorods for Asymmetric Supercapacitors

Zn-MOF decorated bio activated carbon for photocatalytic degradation, oxygen evolution and reduction catalysis

An emerging global necessity for alternative resources combined with maximum catalytic efficiency, low cost, and eco-friendly composite remains a hotspot in the scientific society. Hereby, a novel protocol is approached to design a heterostructure of Zinc MOF decorated on the surface of 2D activated carbon (AC) through a simplistic approach. To begin with, analytical, morphological and spectroscopical studies were performed to identify the functional moieties, cruciate-flower like morphology and oxidative state of atoms present in the composite Zn-MOF @AC. The photocatalytic material aids in degrading both cationic and anionic dye in a UV (254 nm) irradiated environment at a rate of 86.4% and 77.5% within 90 mins. Subsequently, the hybrid materials are coated on the carbon substrate to evaluate the catalytic activity using oxygen evolution and reduction reaction process. The mechanical insight for the catalytic activity relies on the electronic transitions of atoms on the edges of the sheets ascribing to d-d energy levels between the interfacial electron movement. Our composite exhibits an overpotential of 0.7 V and a Tafel slope of 70 mV/dec for the oxygen reduction reaction. This study proposes an alternate approach for developing MOF decorated carbon-based composites for photocatalytic degradability and energy necessity.

Porous hard carbon spheres derived from biomass for high-performance sodium/potassium-ion batteries

Hard carbon is the most attractive anode material for electrochemical sodium/potassium-ion storage. The preparation of hard carbon spheres directly from the broad sources of biomass is of great interest but barely reported. Herein, we developed a simple two-step hydrothermal method to construct porous carbon microspheres directly from the original waste biomass of camellia shells. The porous carbon microspheres have high specific capacities of 250 mAh g^-1and 264.5 mAh g^-1at a current density of 100 mA g^-1for sodium-ion batteries and potassium-ion batteries, respectively. And it has excellent cycle stability for sodium ions and potassium ions outperforming most reported hard carbons, which is mainly attributed to the microporous structure and spherical morphology. The work paves a way to prepare porous hard carbon spheres directly from biomass for alkali metal-ion batteries.

Porous Fe2O3 Nanorods on Hierarchical Porous Biomass Carbon as Advanced Anode for High-Energy-Density Asymmetric Supercapacitors

In this study, a novel negative electrode material was prepared by aligning α-Fe₂O₃ nanorods on a hierarchical porous carbon (HPC) skeleton. The skeleton was derived from wheat flour by a facile hydrothermal route to enhance conductivity, improve surface properties, and achieve substantially good electrochemical performances. The α-Fe₂O₃/HPC electrode exhibits enhanced specific capacitance of 706 F g⁻¹, which is twice higher than that of α-Fe₂O₃. The advanced α-Fe₂O₃/HPC//PANI/HPC asymmetrical supercapacitor was built with an expanded voltage of 2.0 V in 1 M Li₂SO₄, possessing a specific capacitance of 212 F g⁻¹ at 1 A g⁻¹ and a maximum energy density of 117 Wh kg⁻¹ at 1.0 kW kg⁻¹, along with an excellent stability of 5.8% decay in capacitance after 5,000 cycles. This study affords a simple process to develop asymmetric supercapacitors, which exhibit high electrochemical performances and are applicable in next-generation energy storage devices, based on α-Fe₂O₃ hybrid materials.

An Amazingly Simple, Fast and Green Synthesis Route to Polyaniline Nanofibers for Efficient Energy Storage

The major drawbacks of the conventional methods for preparing polyaniline (PANI) are the large consumptions of toxic chemicals and long process durations. This paper presents a remarkably simple and green route for the chemical oxidative synthesis of PANI nanofibers, utilizing sodium phytate as a novel and environmentally friendly plant derived dopant. The process shows a remarkable reduction in the synthesis time and usage of toxic chemicals with good dispersibility and exceedingly high conductivity up to 10 S cm⁻¹ of the resulting PANI at the same time. A detailed characterization of the PANI samples has been made showing excellent relationships between their structure and properties. Particularly, the electrochemical properties of the synthesized PANI as electrode material for supercapacitors were analyzed. The PANI sample, synthesized at pre-optimized conditions, exhibited impressive supercapacitor performance having a high specific capacitance (C_sp) (832.5 Fg⁻¹ and 528 Fg⁻¹ at 1 Ag⁻¹ and 40 Ag⁻¹, respectively) as calculated from galvanostatic charge/discharge (GCD) curves. A good rate capability with a capacitance retention of 67.6% of its initial value was observed. The quite low solution resistance (R_s) value of 281.0 × 10⁻³ Ohm and charge transfer resistance value (R_ct) of 7.44 Ohm represents the excellence of the material. Further, a retention of 95.3% in coulombic efficiency after 1000 charge discharge cycles, without showing any significant degradation of the material, was also exhibited.