A cobalt-pyrrole coordination compound as high performance cathode catalyst for direct borohydride fuel cells

Single laser synthesis of gold nanoparticles-polypyrrole-chitosan on laser-induced graphene for ascorbic acid detection

The simultaneous synthesis of gold nanoparticles (AuNPs) and graphene by laser ablation was demonstrated. The in-situ synthesis was performed by laser ablation of a polymer substrate covered with a gold precursor dispersion. The gold precursor was prepared in a copolymer solution of pyrrole (Py) and chitosan (Chi) to improve the nucleation of gold embedded on the laser-induced graphene electrode (LIGE). The morphology of AuNPs-pPy-Chi/LIGE was studied by scanning electron microscopy and characterized electrochemically by cyclic voltammetry. A comprehensive investigation of the electrochemical and physical features of the AuNPs-pPy-Chi/LIGE was carried out. The parameters of differential pulse voltammetry were adjusted to enhance the response to ascorbic acid (AA). The AuNPs-pPy-Chi/LIGE produced two linear ranges: from 0.25 to 5.00 and 5.00-25.00 mmol L-1. The limit of detection was 0.22 mmol L-1. Hundreds of electrodes were tested to demonstrate the excellent reproducibility of the AuNPs-pPy-Chi/LIGE fabrication. Overall, the proposed electrode allows the successful detection of AA in orange juice products with acceptable accuracy (recoveries = 97 ± 2 to 109.1 ± 0.7). The preparation strategy of the proposed AuNPs-pPy-Chi/LIGE could be adapted to detect other compounds or biomarkers.

Polypyrrole regulates Active Sites in Co-based Catalyst in Direct Borohydride Fuel Cells

Direct borohydride fuel cells (DBFCs) convert borohydride (NaBH4) chemical energy into clean electricity. However, catalytic active site deactivation in NaBH4 solution limits their performance and stability. We propose a strategy to regulate active sites in Co-based catalysts using polypyrrole modification (Co-PX catalyst) to enhance electrochemical borohydride oxidation reaction (eBOR). As an anode catalyst, the synthesized Co-PX catalyst exhibits excellent eBOR performance in DBFCs, with current density of 280 mA ⋅ cm-2 and power density of 151 mW ⋅ cm-2, nearly twice that of the unmodified catalyst. The Co-PX catalyst shows no degradation after 120-hour operation, unlike the rapidly degrading control. In-situ electrochemical attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIRS) and density functional theory (DFT) suggest that polypyrrole-modified carbon support regulate the charge distribution, increasing oxidation state and optimizing adsorption/desorption of intermediates. A possible reaction pathway is proposed. This work presents a promising strategy for efficient polymer-modulated catalysts in advanced DBFCs.

Fabrication of an anion exchange membrane with textured structure for enhanced performance of direct borohydride fuel cells

Developing electrolyte membranes with a simple preparation process and high performance is a top priority for the commercialization of fuel cells. Inspired by solar cell texturing to improve its conversion efficiency, this study prepares a textured membrane by increasing the roughness of a glass plate. The structures of the textured membrane and the flat membrane are characterized and compared. The membranes are assembled in fuel cells for performance testing. The surface area of the textured membrane is 1.27 times that of the flat membrane, which increases the size of the three-phase boundary in fuel cells. The maximum power density of the fuel cell using the textured membrane is 1.17 times of the cell using the flat membrane at 60 °C. The excellent performance of the cell using the textured membrane profit from the enlargement of the three-phase boundary. This work offers a simple way to develop outstanding-performance membranes by changing their surface roughness.

High-Level Oxygen Reduction Catalysts Derived from the Compounds of High-Specific-Surface-Area Pine Peel Activated Carbon and Phthalocyanine Cobalt

Non-platinum carbon-based catalysts have attracted much more attention in recent years because of their low cost and outstanding performance, and are regarded as one of the most promising alternatives to precious metal catalysts. Activated carbon (AC), which has a large specific surface area (SSA), can be used as a carrier or carbon source at the same time. In this work, stable pine peel bio-based materials were used to prepare large-surface-area activated carbon and then compound with cobalt phthalocyanine (CoPc) to obtain a high-performance cobalt/nitrogen/carbon (Co-N-C) catalyst. High catalytic activity is related to increasing the number of Co particles on the large-specific-area activated carbon, which are related with the immersing effect of CoPc into the AC and the rational decomposed temperature of the CoPc ring. The synergy with N promoting the exposure of CoNx active sites is also important. The Eonset of the catalyst treated with a composite proportion of AC and CoPc of 1 to 2 at 800 °C (AC@CoPc-800-1-2) is 1.006 V, higher than the Pt/C (20 wt%) catalyst. Apart from this, compared with other AC/CoPc series catalysts and Pt/C (20 wt%) catalyst, the stability of AC/CoPc-800-1-2 is 87.8% in 0.1 M KOH after 20,000 s testing. Considering the performance and price of the catalyst in a practical application, these composite catalysts combining biomass carbon materials with phthalocyanine series could be widely used in the area of catalysts and energy storage.