Developing efficient and cost-effective materials is crucial for advancing the electrochemical oxygen reduction reaction (ORR). By introducing Co²⁺ ions into formamide, our method prevents rapid Fe²⁺ oxidation to Fe³⁺, promoting the formation of well-defined Fe₃O₄ nanoparticles rather than Fe₂O₃. This study presents a synthesis route for high-performance spinel Fe and Co oxide nanoparticles on N-doped reduced graphene oxide (NRGO). This solvothermal synthesis in formamide yields well-dispersed, ultrafine FeCo(OH)_x nanoparticles (∼5 nm) anchored on NRGO. These nanoparticles can be employed for the formation of spinel Fe_xCo_3−xO₄ oxide nanoparticles, potentially due to their high surface area and strong interaction with the NRGO support. This, in turn, facilitates the successful decoration of highly dispersed spinel Fe_xCo_3−xO₄ oxide nanoparticles (∼30 nm) onto the NRGO support, even after calcination at 900 °C, which represents the critical temperature for conventional graphitization. This unique approach results in significantly reduced particle aggregation compared with that of conventional methods. The (Co)Fe₃O₄-NRGO nanocomposite exhibits remarkable ORR activity, achieving an electron number of ∼3.7 and a current density of 5.01 mA cm⁻² at E = 0.75 V_RHE, comparable to those of commercial Pt/C catalysts. Furthermore, the catalyst exhibits remarkable stability, maintaining a reducing current density that is 42% lower after 40 000 s of uninterrupted operation at 0.75 V_RHE compared with a 75% reduction observed with Pt/C. This exceptional performance is attributed to the strong interaction between the (Co)Fe₃O₄ nanoparticles and NRGO, facilitated by the Co ion precursor during annealing.

中文翻译：

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N掺杂氧化石墨烯负载的FeCo（OH）x纳米片的可扩展合成，用于高效的钴掺杂Fe3O4纳米颗粒氧还原反应电催化


开发高效且具有成本效益的材料对于推进电化学氧还原反应 （ORR） 至关重要。通过将 Co²⁺ 离子引入甲酰胺中，我们的方法可以防止 Fe²⁺ 快速氧化为 Fe³⁺，促进形成定义明确的 Fe₃O₄ 纳米颗粒，而不是 Fe₂O₃。本研究提出了一种在 N 掺杂还原氧化石墨烯 （NRGO） 上制备高性能尖晶石 Fe 和 Co 氧化物纳米颗粒的路线。这种在甲酰胺中的溶剂热合成产生锚定在 NRGO 上的分散良好的超细 FeCo（OH）_x 纳米颗粒 （∼5 nm）。这些纳米颗粒可用于形成尖晶石 Fe_xCo_3−xO₄ 氧化物纳米颗粒，这可能是因为它们的高表面积和与 NRGO 载体的强相互作用。反过来，这又有助于将高度分散的尖晶石 Fe_xCo_3−xO₄ 氧化物纳米颗粒 （∼30 nm） 成功装饰到 NRGO 载体上，即使在 900 °C 下煅烧后，这代表了传统石墨化的临界温度。与传统方法相比，这种独特的方法可显著减少颗粒聚集。（Co）Fe₃O_4-NRGO 纳米复合材料表现出显着的 ORR 活性，在 E = 0 时达到 ∼3.7 的电子数和 5.01 mA ^cm-2 的电流密度。75 V_RHE，与商用 Pt/C 催化剂相当。此外，该催化剂表现出卓越的稳定性，在 0.75 V_RHE 下不间断运行 40 000 秒后，电流密度降低 42%，而使用 Pt/C 观察到的电流密度降低 75%。这种卓越的性能归因于 （Co）Fe₃O₄ 纳米颗粒和 NRGO 之间的强烈相互作用，在退火过程中 Co 离子前驱体的推动下。