Summary
Reduced graphene oxide (RGO) has progressed as one of key emerging carbon for catalyst support material. As an alternative to the conventional RGO precursor, biomass Sengon wood was converted into RGO for use as a noble metal free catalyst support in oxygen reduction reaction (ORR). This work intends to reveal the applicability of Sengon wood‐derived RGO in anchoring/doping iron and nitrogen particles onto its surface and to study its ORR performance in a half‐cell environment. Thin‐sheet layer and highly defective (ID/IG) was gradually obtained at elevated pyrolysis temperature of Sengon wood graphene oxide (GO) at range 700°C to 900°C. As prepared RGO was further doped into catalyst (Fe/N/RGO) through the same pyrolysis procedure at a selected temperature after mixing the GO powder with iron chloride and different nitrogen precursors (urea, choline chloride, and polyaniline) at a fixed ratio. The ORR activity reached a current density up to 2.43 mA/cm2, which in conjunction with smooth multilayer sheet morphology and high graphitic‐N content as the active sites. Stability analysis indicated an 85% current efficiency and only 0.03 V reduction in onset potential on methanol resistant test for Fe/ChoCl/RGO catalyst. This study revealed that Sengon wood‐derived RGO successfully supported Fe‐N‐C catalyst which showed comparable oxygen reduction activity to Pt/C.
Non-precious metals (NPM) such as iron and nitrogen-doped carbon (Fe-N-C) have been actively studied as alternative electrocatalysts to platinum for oxygen reduction reaction (ORR) in proton exchange membrane fuel cell (PEMFC). However, its low stability is associated to the structural morphology of the electrode made of Fe-N-C and its support that has restricted the mass transfer of fuel and product. In this work, it was attempted to assess the role of RGO derived from sengon wood as catalyst support to Fe-N-C catalyst, and study the effect of the Fe-N-C to RGO ratio, on the ORR activity and durability in acidic medium. This work revealed that Fe-N-C/RGO at the weight ratio of 2:0.2 demonstrated the highest onset potential of 0.91 V, with high limiting current density of 5.7 mA/cm2, owing to the uniform active site distribution on the Fe-N-C/RGO surface compared to other samples with different weight ratio. It was indicated in this work that an improve in the kinetic activity was observed with increase operating temperature from 25 to 80 °C. An electron transfer number of 3.91 indicating a complete oxygen reduction process took place on the catalyst. The durability test showed that Fe-N-C/RGO 2:0.2 retained 89 % of its current density at 0.25 V over a duration of 16000 s, higher than that of the benchmark Pt/C. These results have collectively demonstrated a high performance sustainable noble metal-free ORR catalyst for PEMFC applications with proper tailoring the mass ratio of Fe-N-C to RGO support.
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