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

Abstract

• Fe N C and Co N C electrocatalysts derived from bimetallic MOF (Zn/Fe-BZIF and Zn/Co-BZIF). • MOF-molecule composites approach strategy with pyrrole monomers was used. • The acceptable ORR performance was observed for Fe N C in both acidic and alkaline media. • Good ORR stability and low ethanol crossover were observed for Fe-based electrocatalyst. • Fe N C as the cathode in a passive alkaline DEFC could reach promising power density. Herein, a ZIF-molecule-composites approach is applied to make nonprecious metal catalysts (NPMCs) throughout the high-temperature thermal treatment of composite bimetallic zeolite imidazole frameworks (Zn/Fe-BZIF and Zn/Co-BZIF) with pyrrole and FeCl 3 (BZIFs@PPy/FeCl 3 ). 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 optimal ORR catalytic performance with high selectivity (direct four-electron reduction of O 2 to H 2 O), high activity, and durability in both alkaline and acidic environment. In acidic conditions, Fe N C represents the comparable onset potential (E onset = 0.90 V RHE ) to the commercial Pt/C (E onset = 0.95 V RHE ), which also far outperforms the Co-based counterpart (Co N C, E onset = 0.77 V RHE ). In addition, under alkaline conditions, Fe N C represents the highest onset potential (E onset = 1.02 V RHE ) versus Pt/C and Co N C (E onset = 1.0 V and 0.74 V RHE , respectively). Moreover, this optimum electrocatalyst (Fe N C) illustrates excellent stability in alkaline media (95% maintenance of initial current density through 10,000 s chronoamperometric 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.