Electrocatalytic Oxygen Reduction Reaction on 48-Tungsto-8-Phosphate Wheel Anchored on Carbon Nanomaterials

Regardless of great efforts, the development of novel low cost electrocatalysts with high electrocatalytic activity for the oxygen reduction reaction (ORR) remains a real challenge. This is a setback for the mass commercialization of one of the eco-friendliest alternative power sources: fuel cells (FCs). Thus, this work describes the preparation of four composites based on the 48-tungsto-8-phosphate polyanion salt K₂₈Li₅[H₇P₈W₄₈O₁₈₄]·92H₂O (KLi-P₈W₄₈) immobilized on four distinct carbon materials, namely graphene flakes (GF), single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), and N-doped multi-walled carbon nanotubes (N-MWCNT), and their application as ORR electrocatalysts. In alkaline medium, all composites exhibited electrocatalytic activity with onset potentials between 0.71 and 0.94 V vs. RHE, while P₈W₄₈@N-MWCNT presented superior current density (−3.3 mA cm⁻²). A mixed electron process of 2- and 4-electrons is observed for all the composites, supporting the results of % H₂O₂ production. Additionally, low Tafel slopes were obtained (43–82 mV dec^–1) for all composites. The electrocatalysts also showed excellent tolerance to methanol, with current retentions of 91–93%, and good electrochemical stability with current retentions between 67 and 82% after 36,000 s.