Rational design of pyrrolic-N dominated carbon material derived from aminated lignin for Zn-ion supercapacitors.

Developing highly efficient, sustainable carbon cathodes is essential for emerging Zn-ion hybrid supercapacitors (ZICs). Herein, lignin's novel chemical modification (amination) has been developed to produce high quantity pyrrolic-N moieties as active sites. Furthermore, chemically modified amine moieties in lignin are vital as a natural self-activating template to generate hierarchical porosity in the 2D (graphene-like) architecture with exceedingly high surface area (2926.4 m2g-1). The rationally introduced dominated pyrrolic-N moieties boost the Zn-ion storage capacity and reaction kinetics due to the dual energy storage mechanism and efficient charge transfer between pyrrolic-N and Zn+2 ions. Furthermore, the pyrrolic-N species are energetically favorable for the adsorption of Zn+2 ions by the formation of N-Zn+2 chemical bonds. Besides, the nitrogen oxides reduce the intrinsic resistance and induce a more polarized surface, resulting in high wettability and efficient transfer of electrolytes into the pores of hydrophobic carbon materials. Subsequently, the chemically modified lignin-derived activated carbon material (Chem-ACM) as a cathode in ZICs delivers a high capacity of 161.2 mA h g-1 at 1 A g-1 with the admirable energy density of 106.7 W h kg-1 at 897 W kg-1 and excellent retention capacity (94%) after 10,000 cycles. Mainly, the assembled quasi solid-state ZICs using Chem-ACM retains the remarkable storage capacity (202 mA h g-1 at 0.2 Ag-1) even at a high bending angle. Notably, the Chem-ACM has been further employed in symmetric supercapacitors as an electrode, and it displays exceptional specific capacitance of 354 Fg-1 at 0.5 Ag-1 with tremendous energy (43.5 W h kg-1) and the power density (0.53 kW kg-1). Additionally, the charge storage capability of Chem-ACM is positively dependent on high nitrogen contents, and it is extrapolated that pyrrolic-N moieties are dominant active sites. Hence, the designed amination-assisted biocarbon synthesis provides a new way to prepare high nitrogen-containing biocarbon for ZICs and further understand pyrrolic-N species' impact on Zn-ion storage.

Cellulose nanofibers as effective binders for activated biochar-derived high-performance supercapacitors.

Traditional hydrophobic binders can limit supercapacitors' performance by impeding ion accessibility. Herein, we demonstrate the potential of plant-derived environmentally friendly Cellulose Nanofibers (CNF) as binders for biochar (BN-Ac)-based supercapacitors. The CNF binder retains BN-Ac's micropores and improves wettability, while the Polyvinylidene Fluoride (PVDF) binder fills micropores and hinders ion-conductive pathways. The as-synthesized BN-Ac/CNF exhibits a capacitance of 268.4 F g-1 at 5 A g-1, which is 1.4 times higher than that of BN-Ac/PVDF. In addition, the energy density improves from 4.6 to 5.7 Wh kg-1 at 2.1 and 2.5 kW kg-1 power, respectively, for replacing PVDF with CNF. More importantly, BN-Ac/CNF shows outstanding capacitance retention of 96.2 % after 10,000 charge/discharge cycles. The improved wettability and reduced bulk electrolyte resistance by hydrophilic CNF binders are responsible for the electrode's high capacitance. Concurrently, this study showcases a facile strategy for improving supercapacitor performance and a green application of CNF in energy devices.

Chemically modified self-doped biocarbon via novel sulfonation assisted sacrificial template method for high performance flexible all solid-state supercapacitor.

The development of lignin-based carbon electrodes for high-performance flexible, solid-state supercapacitors in next-generation soft and portable electronics, has received much attention. Herein, a self-doped multi-porous lignin-based biocarbon (SUMBC) has been prepared via a simple sulfonation assisted sacrificial template method for the effective formation of oxygenated C-S-C moieties in the carbon network. In this proposed method, the sulfonate moieties in lignin are responsible for the successful decoration of oxygen enriched C-S-C moieties as well as for creating the optimal multilevel porous architecture (ultra-micropores, micropores and mesopores) in the carbon matrix with a large surface area (3149 m2 g-1). Because the sulfonate functionalities yield more sulfur species and induce further defects into carbon framework, in the activation process, these sulfur functionalities produce additional narrow micropores. Benefiting from the above unique feature, the supercapacitor (SC) with the SUMBC electrode delivers excellent capacitive behavior in both acidic (2 M H2SO4) and alkaline (6 M KOH) liquid electrolytes. More prominently, the all-solid state, symmetric supercapacitors assembled by SUMBC show outstanding capacitance of ~140 F g-1 at 0.5 A g-1 in two different devices and reveals high energy density (~5.41 W h kg-1 at 0.5 k W kg-1 power density) and excellent stability. In addition, the solid-state supercapacitors manifest a remarkable flexibility at different bending angles. Hence, the present work provides a new strategy for the preparation of efficient biocarbons via a facile sulfonation assisted sacrificial template method; moreover, the high-performance all-solid supercapacitors based on sulfonated modified lignin has great potential in the field of portable and wearable energy storage devices.

Highly exposed Fe-N4 active sites in porous poly-iron-phthalocyanine based oxygen reduction electrocatalyst with ultrahigh performance for air cathode.

Progress in the development of efficient electrocatalysts for oxygen reduction reactions is imperative for various energy systems such as metal-air batteries and fuel cells. In this paper, an innovative porous two-dimensional (2D) poly-iron-phthalocyanine (PFe-Pc) based oxygen reduction electrocatalyst created with a simple solid-state chemical reaction without pyrolysis is reported. In this strategy, silicon dioxide nanoparticles play a pivotal role in preserving the Fe-N4 structure during the polymerization process and thereby assist in the development of a porous structure. The new polymerized phthalocyanine electrocatalyst with tuned porous structure, improved specific surface area and more exposed catalytic active sites via the 2D structure shows an excellent performance towards an oxygen reduction reaction in alkaline media. The onset potential (E = 1.033 V) and limiting current density (I = 5.58 mA cm-2) are much better than those obtained with the commercial 20% platinum/carbon electrocatalyst (1.046 V and 4.89 mA cm-2) and also show better stability and tolerance to methanol crossover. For practical applications, a zinc-air (Zn-air) battery and methanol fuel cell equipped with the PFe-Pc electrocatalyst as an air cathode reveal a high open circuit voltage and maximum power output (1.0 V and 23.6 mW cm-2 for a methanol fuel cell, and 1.6 V and 192 mW cm-2 for the liquid Zn-air battery). In addition, using the PFe-Pc electrocatalyst as an air cathode in a flexible cable-type Zn-air battery exhibits excellent performance with an open-circuit voltage of 1.409 V. This novel porous 2D PFe-Pc has been designed logically using a new, simple strategy with ultrahigh electrochemical performances in Zn-air batteries and methanol fuel cell applications.

A cyclic peptide accelerates the loading of peptide antigens in major histocompatibility complex class II molecules.

Major histocompatibility complex (MHC)-loading enhancers (MLE) have recently attracted attention because of their ability to enhance the efficacy of peptide immunotherapeutics. As small molecular weight compounds, they influence the loading of peptides in MHC molecules by converting them from a non-receptive to a receptive state. Herein, we report a 14-mer cyclic peptide 1 (CP-1) as a new class of MLE-peptide. This peptide was used to investigate its loading on human leukocyte antigen (HLA)-DR molecules. It was found that CP-1 strongly accelerates peptide-loading on both soluble and cell surface HLA-DR molecules in a dose-dependent manner. The effect was evident for all subsets of HLA-DR tested, including HLA-DRB1*1501, indicating that it acts independently of P1-pocket size, which is the canonical MLE-binding site. Importantly, increased peptide-loading by CP-1 was correlated with improved CD4(+) T cell responses in vitro, while propidium iodide staining indicated low peptide-induced cytotoxicity. Thus, this study revealed a new class of peptide-based enhancers that catalyze peptide-loading by allosteric interactions with MHC molecules. Because of its low cellular cytotoxicity and high MLE activity, it may be useful in stimulating antigen-specific T cell responses for therapeutic purposes.