Wang Yao, Chen Linhui, Mao Zhanxin, Peng Lishan, Xiang Rui, Tang Xianyi, Deng Jianghai, Wei Zidong, Liao Qiang
Chongqing Key Laboratory of Chemical Process for Clean Energy and Resource Utilization, College of Chemistry and Chemical Engineering. Chongqing University, Chongqing 400044, China; Institute of New-Energy and Low-Carbon Technology, Sichuan University, Chengdu 610065, China.
Chongqing Key Laboratory of Chemical Process for Clean Energy and Resource Utilization, College of Chemistry and Chemical Engineering. Chongqing University, Chongqing 400044, China.
Sci Bull (Beijing). 2019 Aug 15;64(15):1095-1102. doi: 10.1016/j.scib.2019.06.012. Epub 2019 Jun 10.
Metal-nitrogen doped carbon catalysts (M-N/C) with abundantly accessible M-N sites, particularly single metal atom M-N/C (SAM-N/C), have been developed as a substitute for expensive Pt-based catalysts. These catalysts are used to increase the efficiency of otherwise sluggish oxygen reduction reactions (ORR) and hydrogen evolution reactions (HER). However, although the agglomerated metal nanoparticles are usually easy to form, they are very difficult to remove due to the protective surface-coating carbon layers, a factor that significantly hampers SAM-N/C fabrication. Herein, we report a one-step pyrolysis approach to successfully fabricate single cobalt atom Co-N/C (SACo-N/C) by using a Co-SCN coordination compound as the metal precursor. Thanks to the decomposition of Co-SCN compound at lower temperature than that of carbon layer deposition, Co-rich particles grow up to larger ones before carbon layers formation. Even though encapsulated by the carbon layers, it is difficult for the large Co-rich particle to be completely sealed. And thus, it makes the Co atoms possible to escape from incomplete carbon layer, to coordinate with nitrogen atoms, and to form SACo-N/C catalysts. This SACo-N/C exhibits excellent performances for both ORR (half-wave potential of 0.878 V) and HER (overpotential at 10 mA/cm of 178 mV), and is thus a potential replacement for Pt-based catalysts. When SACo-N/C is integrated into a Zn-O battery, battery with high open-circuit voltage (1.536 V) has high peak power density (266 mW/cm) and large gravimetric energy density (755 mA h/g) at current densities of 100 mA/cm. Thus, we believe that this strategy may offer a new direction for the effective generation of SAM-N/C catalysts.
具有大量可及M-N位点的金属-氮掺杂碳催化剂（M-N/C），特别是单金属原子M-N/C（SAM-N/C），已被开发作为昂贵的铂基催化剂的替代品。这些催化剂用于提高原本缓慢的氧还原反应（ORR）和析氢反应（HER）的效率。然而，尽管团聚的金属纳米颗粒通常易于形成，但由于保护性的表面包覆碳层，它们很难去除，这一因素显著阻碍了SAM-N/C的制备。在此，我们报道了一种一步热解方法，通过使用Co-SCN配位化合物作为金属前驱体，成功制备了单钴原子Co-N/C（SACo-N/C）。由于Co-SCN化合物在低于碳层沉积的温度下分解，富钴颗粒在碳层形成之前生长成更大的颗粒。即使被碳层包裹，大的富钴颗粒也难以被完全密封。因此，Co原子有可能从不完全的碳层中逸出，与氮原子配位，形成SACo-N/C催化剂。这种SACo-N/C在ORR（半波电位为0.878 V）和HER（在10 mA/cm²时过电位为178 mV）方面均表现出优异的性能，因此是铂基催化剂的潜在替代品。当SACo-N/C集成到锌-氧电池中时，在100 mA/cm²的电流密度下，具有高开路电压（1.536 V）的电池具有高峰功率密度（266 mW/cm²）和大的重量能量密度（755 mA h/g）。因此，我们认为这种策略可能为有效制备SAM-N/C催化剂提供一个新的方向。
