Metal to metal electron transfer in {111} faceted rice-grain like nanoparticles of Mn-wolframite for oxygen reduction reaction

Commercial interest in Pt and Pt-based catalysts is hindered by their high cost. Herein, we have synthesized {111} faceted rice-grain like nanoparticles of p-MnWO₄ with wolframite structure by a polyol method, and applied as catalysts for the ORR in alkaline electrolyte. It enabled a transfer of electron from t_2g orbital of Mn 3d to the empty antibonding orbital of W 5d, producing plentiful Mn³⁺ states towards ORR. Moreover, it showed superior ORR activity to CoWO₄ and FeWO₄ prepared similarly, and to a h-MnWO₄ prepared by a hydrothermal procedure. p-MnWO₄ exhibited lowest negative onset potential (0.92 V vs RHE) and smallest Tafel slope (50 mV dec^‑1). Moreover, it achieved highest redox reaction mediated current density (-4.2 mA cm^-2), attributable to Mn³⁺ to Mn²⁺ reduction and promising stability (96.6 %) over 6 h Excellent performance of p-MnWO₄ is associated with optimal O₂ adsorption energies caused by metal to metal charge transfer and {111} faceted rice-grain like p-MnWO₄ nanoparticles.