Copper ferrite nanospheres composites mixed with carbon black to boost the oxygen reduction reaction

Abstract

Copper ferrite nanospheres (CFNS) were prepared by a solvothermal method and they were calcined at different temperatures ranging from 200−600 °C, resulting in CFNS-based materials with different both surface chemistry and structural features, which play a crucial role in the electrocatalytic activity of carbon black-containing CFNS catalysts towards the oxygen reduction reaction (ORR). The study was addressed to elucidate which kind of crystalline phases, as well as surface chemistry of CFNS were responsible for enhancing the electrocatalytic activity in ORR. The pristine CFNS and CFNS200 (calcined at 200 °C) exhibited cubic spinel, cuprite and copper as main crystalline phases. In the case of CFNS400, it also displays the cubic phase along with a new phase (tenorite). Apart from the tenorite, CFNS600 exhibited hematite, and the cubic phase of spinel shifted to the tetragonal phase. Regarding the electrocatalytic activity in ORR, the CFNS revealed poor activities compared to those of carbon black-containing CFNS catalysts. The high-performing catalyst was CFNS400/Vulcan in terms of current density and onset potential along with its good stability. This improvement may be assigned to both the chemical composition and structure.