In Situ Synthesis of Co3O4 Nanoparticles on N-Doped Biochar as High-Performance Oxygen Reduction Reaction Electrocatalysts Matos, Renata Manuel, Jorge V. Fernandes, António J.S. Abdelkader Fernández, Víctor Karim F. Peixoto, Andreia Fernandes, Diana M. Biochar Electrocatalyst Oxygen reduction Cobalt oxide The development of sustainable and high-performance oxygen reduction reaction (ORR) electrocatalysts is fundamental to fuel cell implementation. Non-precious transition metal oxides present interesting electrocatalytic behavior, and their incorporation into N-doped carbon supports leads to excellent ORR performance. Herein, we prepared a shrimp shell-derived biochar (CC), which was doped with nitrogen via a ball milling approach (N-CC), and then used as support for Co3O4 nanoparticles growth (N-CC@Co3O4 ). Co3O4 loading was optimized using three different amounts of cobalt precursor: 1.56, 2.33 and 3.11 mmol in N-CC@Co3O4_1, N-CC@Co3O4_2 and N-CC@Co3O4_3, respectively. Interestingly, all prepared electrocatalysts, including the initial biochar CC, presented electrocatalytic activity towards ORR. Both N-doping and the introduction of Co3O4 NPs had a significant positive effect on ORR performance. Meanwhile, the three composites showed distinct ORR behavior, demonstrating that it is possible to tune their electrocatalytic performance by changing the Co3O4 loading. Overall, N-CC@Co3O4_2 achieved the most promising ORR results, displaying an Eonset of 0.84 V vs. RHE, jL of −3.45 mA cm−2 and excellent selectivity for the 4-electron reduction (n = 3.50), besides good long-term stability. These results were explained by a combination of high content of pyridinic-N and graphitic-N, high ratio of pyridinic-N/graphitic-N, and optimized Co3O4 loading interacting synergistically with the porous N-CC support 2025-07-28T11:37:12Z 2025-07-28T11:37:12Z 2024-12-23 journal article Matos, R.; Manuel, J.V.; Fernandes, A.J.S.; Abdelkader-Fernández, V.K.; Peixoto, A.F.; Fernandes, D.M. In Situ Synthesis of Co3O4 Nanoparticles on N-Doped Biochar as High-Performance Oxygen Reduction Reaction Electrocatalysts. Catalysts 2024, 14, 951. https://doi.org/10.3390/catal14120951 https://hdl.handle.net/10481/105775 10.3390/catal14120951 eng http://creativecommons.org/licenses/by/4.0/ open access Atribución 4.0 Internacional MDPI