Synergistic effects of carbon nanotubes on α-MnO2 electrocatalysts for improved oxygen reduction in alkaline fuel cells

The Alkaline Membrane Fuel Cell (AMFC), is a device crucial for electrochemical energy production through the oxygen reduction reaction (ORR), conventionally relies on platinum catalysts. However, the challenges of excessive cost and inadequate stability in alkaline environments have hindered its widespread commercialization. Alpha manganese dioxide (alpha MnO2), with diverse applications in energy and environmental domains, has potential as an alternative catalyst due to its lower metal costs and comparable catalytic activity. This study focuses on the synthesis of alpha MnO2 nanotubes through controlled environment temperature, and integration with carbon nanotubes (CNTs). Optimizing the gas pressure and temperature during synthesis resulted in structural changes in alpha MnO2 nanotubes, with a notable increase in catalytic behavior at elevated temperatures. The sample treated at 450 degrees C and mixed with CNTs (CNT-MO450) demonstrated outstanding ORR performance and prolonged stability in an alkaline medium. Furthermore, the CNT-MO450 exhibited the highest current density of -5.2 mA/cm(2) at a potential of 0.65 V vs RHE, a peak power density of 73 mW/cm(2) (comparable to Pt/C at 95 mW/cm(2)), and a charge transfer resistance of 310 Omega. The temperature treatment affected the alpha MnO2 nanotubes, which resulted in increased length at an optimal temperature, leading to a larger surface area. This enhancement in surface area is crucial to improved catalytic activity, electrical conductivity, and extended stability during operation in alkaline media. The findings suggest that CNT-MO450 catalysts hold promise as a cost-effective and stable alternative catalyst for AMFCs.