Designing one-compartment H2O2 fuel cell using electroactive phenalenyl-based [Fe2(hnmh-PLY)3] complex as the cathode material

Abstract

The sustainable chemical energy of H₂O₂ as a fuel and an oxidant in an advantageous single-compartment fuel cell design can be converted into electric energy, which requires molecular engineering to design suitable cathodes for lowering the high overpotential associated with H₂O₂ reduction. The present work covers the synthesis and structural characterization of a novel cathode material, [Fe^III₂(hnmh-PLY)₃] complex, 1, designed from a PLY-derived Schiff base ligand (E)-9-(2-((2-hydroxynaphthalen-1-yl)methylene)hydrazineyl)-1H-phenalen-1-one, hnmh-PLYH₂. Complex 1, when coated on the surface of a glassy carbon electrode (GC-1) significantly catalyzed the reduction of H₂O₂ in an acidic medium. Therefore, a complex 1 modified glassy carbon electrode was employed in a one-compartment H₂O₂ fuel cell operated in 0.1 M HCl with Ni foam as the corresponding anode to produce a high open circuit potential (OCP) of 0.65 V and a peak power density (PPD) of 2.84 mW cm⁻². CV studies of complex 1 revealed the crucial participation of two Fe(III) centers for initiating H₂O₂ reduction, and the role of coordinated redox-active PLY units is also highlighted. In the solid state, the π-conjugated network of coordinating (hnmh-PLY) ligands in complex 1 has manifested interesting face-to-face π–π stacking interactions, which have helped the reduction of the complex and facilitated the overall catalytic performance.