Highly durable and stable Fe-N-C catalyst for oxygen reduction reaction in acidic medium

Fuel cells are one the promising energy generation devices that are clean and environmentally friendly and use alternative fuels such as hydrogen and methanol by converting chemical energy to electrical energy through a pair of redox reactions. However, its large-scale application is hindered by its sluggish oxygen reduction reaction (ORR) at the cathode and requires a highly active yet expensive Pt/C catalyst. To overcome this, researchers have started to look at the use of non-noble metal as the ORR catalyst. Therefore, this work is intended to introduce Fe-based non-noble metal catalyst and investigate the effect of different Fe-N-C morphologies prepared from different precursors, on the catalyst’s durability and stability during the operation of ORR in an acidic medium. Three different morphologies, namely hollow sphere (HS), amorphous bulky structure (B) and needle-like structure (N) of Fe-N-C were synthesized at the fixed Fe precursor composition. ZIF-8, poly(aniline) and 10,10′-Dibromo-9,9′-bianthry were used as the respective synthesis precursor to produce N-doped carbon with the aforementioned morphologies. The morphology study, crystal structure, pore characteristics and elemental compositions were determined on the samples. To investigate the electrocatalytic activity of the catalysts towards the ORR, a three-electrode setup was used for the electrochemical analysis with 0.1 M HClO4 as the acidic electrolyte. Accelerated durability test (ADT) and chronoamperometry test were used, respectively for the durability and stability study of the catalyst. From the electrochemical test, Fe-N-C_HS shows the highest onset potential (Eonset = 0.83 V vs RHE) compared to Fe-N-C_B (Eonset = 0.8 V vs RHE) and Fe-N-C_N (Eonset = 0.55 V vs RHE). Through the ADT test, Fe-N-C_HS demonstrated active sites activation with increase in half wave potential after 5,000 ADT cycles. In addition, this sample demonstrating the highest current retention of 80 %, compared to other samples and Pt/C, after the 10,000 s chronoamperometry test.