Experimental investigation and comprehensive analysis of performance and membrane electrode assembly parameters for proton exchange membrane fuel cell at high operating temperature

Abstract：The future trend in proton exchange membrane fuel cells (PEMFCs) is developing towards higher operating temperatures, although the current lack of comprehensive investigation into the PEMFC characteristics at elevated temperatures. This work provides a comprehensive summary of commonly used test methods and data processing methods for PEMFCs, encompassing polarization decomposition, electrochemical impedance spectroscopy (EIS) processing methods, electrochemical surface area (ECSA) and hydrogen crossover current density (iH) calculation methods. Experiments on PEMFC performance and membrane electrode assembly (MEA) parameters at 80 to 95 ℃ under various humidities are conducted. The experimental results indicate that elevated temperatures contribute to increased ohmic loss and reduced mass transfer and activation losses. Increased temperature can substantially accelerate the reaction rate and compensate for the decrease in ECSA. The ECSA decreases at elevated temperatures, and higher temperatures will result in a faster drop. The iH demonstrates an increase with both temperatures and humidities, with higher humidities leading to faster growth. Based on the comprehensive test and analysis methods for PEMFC, this study could enhance understanding and provide valuable guidance for PEMFC performance variation laws at high operating temperatures.

30

2024

/

07

Heterojunction catalysts of ultra-thin carbon layer activated Platinum nanoparticles for bifunctional pH-universal hydrogen evolution reaction and oxygen reduction reaction

Heterojunction catalysts of ultra-thin carbon layer activated Platinum nanoparticles for bifunctional pH-universal hydrogen evolution reaction and oxygen reduction reaction

Abstract：Platinum catalysts are widely used in electrocatalytic water splitting for the hydrogen evolution reaction and in hydrogen fuel cells for the oxygen reduction. Nonetheless, the practical use of the noble metal platinum in commercial applications faces significant challenges due to its exorbitant cost and the intricate nature of its synthetic methods. In this work, nitrogen-doped carbon layers covering platinum particles (Pt@NCL) are uniformly distributed on carbon nanofiber (CNF) substrates to synthesize heterojunction catalysts (Pt@NCL-CNF). Multiple characterization methods reveal that the nanoscale ultra-thin carbon layer successfully activates platinum nanoparticles and creates a tremendous accumulation of valence electrons at the interface of the heterojunction catalysts. Furthermore, the greater the number of defects produced in the ultra-thin carbon layer of Pt@NCL-CNF during the reaction, the more active sites are exposed. Therefore, Pt@NCL-CNF exhibits much better hydrogen evolution reaction and oxygen reduction reaction performance in pH-universal electrolytes than the commercial carbon-supported platinum (Pt/C) catalyst. This study elucidates the reaction mechanism, highlighting the crucial role of the ultra-thin carbon layer within the catalyst, and also confirms the catalyst performance in device applications. The proposed method can provide a simple and feasible mass-produced approach for the preparation and application of high performance low platinum catalyst.

30

2024

/

07

< 1234 >