Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ on N-doped mesoporous carbon derived from organic waste as a bi-functional oxygen catalyst

Developing cost-effective oxygen electrocatalysts is critical to the wide application of renewable energy technologies including fuel cells, electrolyzers, and metal-air batteries. In this work, we report Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF) on nitrogen-doped mesoporous carbon (NC) as a novel and highly-active bi-functional catalyst for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The NC is prepared using organic waste, namely banana peels. The carbonization, heteroatom doping, and surface functionalization are achieved simultaneously during a facile synthesis process. The obtained NC is characterized by large mesopores with a specific surface area of 457.6 m² g⁻¹. The electrochemical measurements reveal that, the current density of the BSCF/NC in 0.1 mol L⁻¹ KOH reaches −3 mA cm⁻² at 0.74 V and 10 mA cm⁻² at 1.58 V vs. the reversible hydrogen electrode. Furthermore, the hybrid shows a smaller onset potential and larger current density towards both ORR and OER in comparison to composites made of BSCF and common commercial carbon supports, including acetylene black (AB) carbon, activated carbon (AC), and Vulcan XC-72 carbon. Besides enhancing the surface area and the dispersion of BSCF, the electronic interaction between BSCF and NC likely renders the enhanced activity.