Fe–Co based synergistic catalytic graphitization of biomass: Influence of the catalyst type and the pyrolytic temperature

To produce porous graphite and hydrogen sustainably, a series of monometallic catalysts (e.g., Fe, Co, and Ni) and bimetallic catalysts (e.g., Fe–Co, Fe–Ni) were investigated for biomass graphitization. Experiments were conducted in a vertical fixed-bed system, and the influence of the catalyst type and the pyrolytic temperature were investigated. Further, the obtained sustainable porous graphite was employed in the oxygen reduction reaction. The results showed that the hydrogen yield, degree of char graphitization, and porosity changed when the catalyst type is varied. Among the monometallic catalysts, Fe showed a high degree of char graphitization and the largest surface area, while Co showed the highest hydrogen yield (7.19 mmol/g biomass). Due to the presence of Fe–Co alloys and the homogeneous distribution of Fe and Co, the bimetallic Fe–Co catalyst afforded a higher hydrogen yield (7.51 mmol/g), larger pore volume, and higher degree of char graphitization than the monometallic Fe and Co catalysts. The optimal pyrolytic temperature was found to be 850 °C, which ensured a balance between the char porosity and graphitization. Furthermore, the porous graphite obtained with the Fe–Co catalyst exhibited an outstanding electrochemical performance for the ORR, delivering a half-wave potential of 0.79 V under alkaline conditions, and high stability and outstanding electrochemical performance in the oxygen reduction reaction.