Nitrogen-functionalized catalyst synthesized using spent coffee ground biochar-cobalt hybrid for oxygen reduction reaction via pyrolysis and ball-milling
Mohamad Ayoub , Abdul Hai Alami , Mohammad Ali Abdelkareem , A.G. Olabi
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引用次数: 0
Abstract
In this work, oxygen reduction reaction (ORR) catalysts were developed from a precursor of spent coffee ground-based biochar. Nitrogen doping was achieved via urea addition preceding a pyrolysis synthesis process, yielding nitrogen-doped biochar (NDB). Cobalt was deposited onto the NDB surface using a non-conventional ball-milling procedure. The microstructure of the synthesized samples was studied through Scanning Electron Microscopy (SEM), where a rather distorted surface, highlighted by prominent wrinkles (which doubled the surface area at 50.58 m2/g), was shown for nitrogen-doped samples. Moreover, the high energy ball-milling technique shows an almost perfect coverage of cobalt nanoparticles on the biochar surface through SEM/EDS and Raman results. Additionally, electrochemical testing was conducted using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Cyclic voltammetry measurements conducted under nitrogen (inert) and oxygen-saturated alkaline solution (0.1 M KOH) conditions showed that nitrogen doping enhances the oxygen reduction reaction current (-1 vs -0.59 mA.cm−1 at -0.3 V vs Hg/HgO) and slightly reduces the onset potential compared to pristine biochar. Depositing cobalt onto the NDB surface had a minor adverse effect on the onset potential, but significantly increased the oxygen reduction reaction current, reaching a value of -2.09 mA.cm−2 at -0.3 V vs Hg/HgO. All catalysts were compared to a commercial carbon supported platinum catalyst (Pt10%C) to showcase the potential room of improvement for the developed catalysts.
在这项研究中,利用废咖啡渣生物炭为前驱体开发了氧还原反应(ORR)催化剂。在热解合成过程之前,通过添加尿素实现了氮掺杂,得到了氮掺杂生物炭(NDB)。采用非常规球磨程序将钴沉积到 NDB 表面。通过扫描电子显微镜(SEM)研究了合成样品的微观结构,结果显示掺氮样品的表面相当扭曲,突出表现为明显的皱纹(使表面积增加了一倍,达到 50.58 m2/g)。此外,高能球磨技术的 SEM/EDS 和拉曼结果表明,钴纳米颗粒几乎完美地覆盖了生物炭表面。此外,还使用循环伏安法(CV)和电化学阻抗谱法(EIS)进行了电化学测试。在氮气(惰性)和氧气饱和碱性溶液(0.1 M KOH)条件下进行的循环伏安测量表明,与原始生物炭相比,氮掺杂增强了氧还原反应电流(-1 vs -0.59 mA.cm-1 at -0.3 V vs Hg/HgO),并略微降低了起始电位。在 NDB 表面沉积钴对起始电位的不利影响较小,但却显著提高了氧还原反应电流,在 -0.3 V 对 Hg/HgO 时达到 -2.09 mA.cm-2 的值。所有催化剂都与商用碳支撑铂催化剂(Pt10%C)进行了比较,以展示所开发催化剂的潜在改进空间。