RGO-templated lignin-derived porous carbon materials for renewable high-performance supercapacitors

Preparation of cathode catalysts for efficient direct lignin fuel cells by nitrogen doping reduction of oxidized graphene with phthalocyanine iron and Kraft lignin

Direct lignin fuel cells (DLFC) are one of the important forms of high value-added utilization of lignin. In this study, lignin was studied not only as a fuel but also as a catalyst. Specifically, Kraft lignin was modified with ZnCl2, KOH and THF (Tetrahydrofuran) respectively, and added to the catalyst after activation. The results of scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive spectrometer (EDS), Brunauer - Emmett - Teller (BET), X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FT-IR) and Raman spectra shown that AL/FePc-NrGO (activated lignin/iron phthalocyanine/nitrogen-doped reduction of graphene oxide) three-dimensional composite catalyst has been synthesized. The results showed that KOH-activated Kraft lignin had the best performance as an oxygen reduction reaction (ORR) catalyst, with a half-wave potential (E1/2) of 0.73 V and a limiting diffusion current density of 4.3 mA cm-1. The THF-modified catalyst showed similar stability and methanol resistance to 20 % Pt/C at ORR. The ORR catalyst applied to the DLFC has the best electrical performance with an open circuit voltage (OCV) was 0.53 V and the maximum power density it could reach 95.29 mW m-2 when the catalyst was modified with THF. It is encouraging that the AL/FePc-NrGO catalyst has better-generated electricity performance than 20 % Pt/C. This work has provided a new idea for developing non-noble metal catalysts and studying direct biomass liquid fuel cells.

Recent advances in biopolymers-based carbon materials for supercapacitors

Supercapacitors as potential candidates for novel green energy storage devices demonstrate a promising future in promoting sustainable energy supply, but their development is impeded by limited energy density, which can be addressed by developing high-capacitance electrode materials with efforts. Carbon materials derived from biopolymers have received much attention for their abundant reserves and environmentally sustainable nature, rendering them ideal for supercapacitor electrodes. However, the limited capacitance has hindered their widespread application, resulting in the proposal of various strategies to enhance the capacity properties of carbon electrodes. This paper critically reviewed the recent research progress of biopolymers-based carbon electrodes. The advances in biopolymers-based carbon electrodes for supercapacitors are presented, followed by the strategies to improve the capacitance of carbon electrodes which include pore engineering, doping engineering and composite engineering. Furthermore, this review is summarized and the challenges of biopolymer-derived carbon electrodes are discussed. The purpose of this review is to promote the widespread application of biopolymers in the domain of supercapacitors.

Recent advances in lignin-based carbon materials and their applications: A review

As the most abundant natural aromatic polymer, tens of million of tons of lignin produced in paper-making or biorefinery industry are used as fuel annually, which is a low-value utilization. Moreover, burning lignin results in large amounts of carbon dioxide and pollutants in the air. The potential of lignin is far from being fully exploited and the search for high value-added application of lignin is highly pursued. Because of the high carbon content of lignin, converting lignin into advanced carbon-based structural or functional materials is regarded as one of the most promising solutions for both environmental protection and utilization of renewable resources. Significant progresses in lignin-based carbon materials (LCMs) including porous carbon, activated carbon, carbon fiber, carbon aerogel, nanostructured carbon, etc., for various valued applications have been witnessed in recent years. Here, this review summarized the recent advances in LCMs from the perspectives of preparation, structure, and applications. In particular, this review attempts to figure out the intrinsic relationship between the structure and functionalities of LCMs from their recent applications. Hopefully, some thoughts and discussions on the structure-property relationship of LCMs can inspire researchers to stride over the present barriers in the preparation and applications of LCMs.

Nitrogen-rich accordion-like lignin porous carbon via confined self-assembly template and in-situ mild activation strategy for high-performance supercapacitors

Nitrogen-doped porous carbons have emerged as promising electrode materials for supercapacitors. However, the precise control of carbon geometry and the effective doping method remain challenging. Herein, a confined self-assembly template and in-situ mild activation strategy is proposed to prepare cubic lignin composite precursor, followed by co-pyrolysis with melamine at a high temperature for nitrogen-doped hierarchical porous carbons (N-HPLCs). The zinc oxalate template has the coupling effect of confinement and mild activation during carbonization, which not only prevents the restacking of the carbon matrix but also generates zinc cyanamide intermediate to avoid excessive loss of nitrogen species. The optimized N-HPLCs exhibit an accordion-like framework with interconnected porous sheets, ultrahigh edge-nitrogen doping level (up to 12.20 at.%), and a total nitrogen doping level of 14.09 at.%. Consequently, it shows a high gravimetric capacitance of 354 F/g at 0.2 A/g, an extraordinary surface-area-normalized capacitance of 82.1 ± 0.2 μF/cm², and good rate capability in supercapacitor applications. Moreover, the fabricated coin-type symmetric supercapacitor displays a high energy density of 12.9 Wh/kg at 161.9 W/kg and superior cycling stability with a 99.5% capacitance retention after 16,000 cycles at 2.0 A/g. This work offers a novel method for preparing nitrogen-enriched lignin-derived carbon for high-performance supercapacitors.

Review on the preparation and application of lignin-based carbon aerogels

Carbon aerogels (CAs) are excellent carrier materials with a large surface area and high porosity. In addition to the above-mentioned wonderful characteristics, aerogel with lignin as a precursor is also a material with high bioactivity and degradability. Lignin carbon aerogels (LCAs) have a wide range of applications, and can be used in supercapacitors, adsorbents and catalysts, etc., but their preparation process is more complex. In this paper, we review the preparation and influencing factors of LCAs, analyze their properties and structural characterization, and aim to provide references for the optimal preparation, effective characterization, and expansion of applications of LCAs.