Harnessing inherently hierarchical microstructures of plant biomass to construct three-dimensional nanoporous nitrogen-doped carbons as efficient and durable oxygen reduction electrocatalysts

Biomass-Derived Carbon Materials for Electrochemical Sensing: Recent Advances and Future Perspectives

In recent years, biomass carbon materials have received widespread attention in the field of electrochemical sensors. As a new type of renewable green energy, biomass carbon has the advantages of low cost and abundant resources. After special treatment, it can be used as an ideal electrode material. Since biomass carbon materials have diverse sources and their morphology is difficult to control, researchers have conducted in-depth research on their preparation process, morphology regulation and application. This review summarizes different biomass carbon structures and their preparation methods and explores the applications of these materials in electrochemical sensors. Modification of biomass carbon materials through pretreatment, physical and chemical activation, heteroatom doping, metal compound composite and other methods can make up for the deficiencies in its pore structure, electrical conductivity and surface wettability, thereby improving its electrochemical performance. The effects of different biomass sources, functional groups, constituent elements and modification methods on the morphology, structure and electrochemical properties of biomass carbon materials are discussed, and the applications of this type of material in biological molecules, heavy metal ions and pesticide residues are reviewed. Biomass carbon-based materials show great application potential and development prospects in the field of electrochemical sensors.

Incorporation of Pt-Cr nanoparticles into highly porous MOF-5 as efficient oxygen reduction electrocatalysts

Developing new materials that can enhance the efficiency of energy conversion and storage systems is critical to meeting the rising energy demand of low-carbon economies. Mesoporous materials have the advantages of large specific surface area and multiple channels, which can increase efficiency and flexibility in terms of energy and power density. An active catalyst for oxygen reduction reaction (ORR) based on Pt-Cr nanoparticles with ultralow Pt content (0.90 wt%) has been studied in this paper. In contrast, electrocatalyst Pt/Cr/NPC-900 exhibited an ORR activity with onset potential (E _o) of 1.01 V vs. RHE in an alkaline solution that was superior to commercial Pt/C (20 wt%) (0.96 V vs. RHE). The presence of metal oxides and optimal Pt content enhanced the ORR activity. Therefore, the synergistic effect of the high surface area increased charge transfer, and excellent structural stability can achieve significant ORR efficiency, which is conducive to excellent activity. These findings provide a new perspective for economical and practical ORR electrocatalysts to be designed and synthesized rationally.

Ultrasound-assisted transformation from waste biomass to efficient carbon-based metal-free pH-universal oxygen reduction reaction electrocatalysts

Efficient carbon-based nitrogen-doped electrocatalysts derived from waste biomass are regarded as a promising alternative to noble metal catalysts for oxygen reduction reaction (ORR), which is crucial to fuel cell performance. Here, coconut palm leaves are employed as the carbon source and a series of nitrogen-doped porous carbons were prepared by virtue of a facile and mild ultrasound-assisted method. The obtained carbon material (ANDC-900-10) conveys excellent pH-universal catalytic activity with onset potentials (E_onset) of 1.01, 0.91 and 0.84 V vs. RHE, half-wave potentials (E_1/2) of 0.87, 0.74 and 0.66 V vs. RHE and limiting current densities (J_L) of 5.50, 5.45 and 4.97 mA cm^-2 in alkaline, neutral and acidic electrolytes, respectively, prevailing over the commercial Pt/C catalyst and, what's more, ANDC-900-10 displays preeminent methanol crossover resistance and long-term stability in the broad pH range (0-13), thanks to its abundant hierarchical nanopores as well as effective nitrogen doping with high-density pyridinic-N and graphitic-N. This work provides sonochemical insight for underpinning the eco-friendly approach to rationally designing versatile metal-free carbon-based catalysts toward the ORR at various pH levels.

Dual potassium salt-assisted lyophilization of natural fibres for the high-yield synthesis of one-dimensional carbon microtubes for supercapacitors and the oxygen reduction reaction

Natural fibre-derived carbon microtubes exhibit excellent performances as supercapacitor electrodes and oxygen reduction electrocatalysts via dual-potassium-salt-assisted freeze-drying and post-nitrogen doping.