Metal-nitrogen co-doped hierarchical porous carbon derived from the bimetallic metal-organic framework as ORR electrocatalyst for passive alkaline direct ethanol fuel cell

Herein, a ZIF-molecule-composites approach is applied to make nonprecious metal catalysts (NPMCs) through-out the high-temperature thermal treatment of composite bimetallic zeolite imidazole frameworks (Zn/Fe-BZIF and Zn/Co-BZIF) with pyrrole and FeCl3 (BZIFs@PPy/FeCl3). The prepared electrocatalysts are characterized by XRD, FESEM, TEM, EDX-mapping, BET, Raman, and XPS. The Fe-N-C electrocatalyst shows superior to its counterpart (Co-N-C) for ORR (oxygen reduction reaction). Iron-based MOF electrocatalyst exhibits the opti-mal ORR catalytic performance with high selectivity (direct four-electron reduction of O2 to H2O), high activ-ity, and durability in both alkaline and acidic environment. In acidic conditions, Fe-N-C represents the comparable onset potential (Eonset= 0.90 VRHE) to the commercial Pt/C (Eonset= 0.95 VRHE), which also far outperforms the Co-based counterpart (Co-N-C, Eonset= 0.77 VRHE). In addition, under alkaline condi-tions, Fe-N-C represents the highest onset potential (Eonset= 1.02 VRHE) versus Pt/C and Co-N-C (Eonset= 1.0 V and 0.74 VRHE, respectively). Moreover, this optimum electrocatalyst (Fe-N-C) illustrates excellent stability in alkaline media (95% maintenance of initial current density through 10,000 s chronoam-perometric measurements). Finally, passive alkaline direct ethanol fuel cell performance is evaluated to obtain the activity of prepared electrocatalysts in alkaline media. The results showed promising fuel cell performance, especially for the Fe-based electrocatalyst (Fe-N-C-3 h). The current work provides a new horizon towards representing pioneer nonprecious metal and nitrogen-doped carbonaceous structures with an excellent ORR activity and direct ethanol fuel cell performance.

Automated summary

This study demonstrates the synthesis of nonprecious metal catalysts (NPMCs) through high-temperature thermal treatment of bimetallic zeolite imidazole frameworks. The Fe-N-C electrocatalyst exhibits superior performance compared to its counterpart (Co-N-C) for oxygen reduction reaction (ORR) and shows excellent stability in both alkaline and acidic environments. This work provides a new approach for the development of nonprecious metal and nitrogen-doped carbonaceous structures with excellent ORR activity and direct ethanol fuel cell performance.