Cobalt nanoparticle supported on layered double hydroxide: Effect of nanoparticle size on catalytic hydrogen production by NaBH4 hydrolysis
Cobalt nanoparticle supported on layered double hydroxide: Effect of nanoparticle size on catalytic hydrogen production by NaBH4 hydrolysis
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DOI：
10.1016/j.envpol.2021.117990
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发表时间：
2021-09-13
影响因子：
8.9
通讯作者：
Tomoshige, Ryuichi
中科院分区：
文献类型：
--
作者：
Mahpudz, Aishah;Lim, Siu Ling;Tomoshige, Ryuichi
硼氢化钠 (NaBH4) 的催化水解是一种为便携式设备提供清洁氢 (H-2) 能源的有前途的方法。因此，设计一种在这种水解中表现良好的非贵金属催化剂至关重要。通过改变与 LDH 主体进行离子交换的钴柠檬酸根阴离子（Co-柠檬酸根）前体的浓度，合成了负载在镁铝层状双氢氧化物（LDH）上的具有不同平均直径的钴纳米粒子（Co-NPs）。然后用 NaBH4 还原 Co-柠檬酸盐嵌入的 LDH，形成 Co-NP。 X 射线衍射 (XRD) 和傅里叶变换红外光谱 (FT-IR) 显示了成功插层的证据。透射电子显微镜（TEM）和扫描TEM（STEM）观察表明Co-NPs呈金属态，并且它们的平均直径随着柠檬酸钴溶液的浓度而增加。氮物理吸附等温线显示化学还原后LDHs的表面结构从无孔转变为介孔，这表明Co-NPs形成于LDHs的层间。 NaBH4在25℃下的催化水解表明，由6 mM Co-柠檬酸盐溶液合成的催化剂显示出最高的H-2生成速率，为4520 +/- 251 mL min(-1).gCo(-1)，表明该催化剂具有最佳的Co-NP尺寸。与之前报道的无载体钴和许多其他载体钴基催化剂相比，这种活性可以被认为相对较高。还清楚地表明，LDH 上负载的 Co-NP 的尺寸可能是一个重要参数，因为它允许反应物更好地接触活性催化剂表面以获得最大活性。对于该最佳催化剂，活化能为56.9 kJ mol(-1)。催化剂在相同条件下重复测试5次后，虽然能达到几乎相同的转化率，但催化活性逐渐下降。总体而言，LDH 负载的 Co-NP 在用于 H-2 能源生产方面具有巨大的潜力。
Catalytic hydrolysis of sodium borohydride (NaBH4) is a promising method to provide clean hydrogen (H-2) energy for portable devices. Therefore, designing a non-noble metal catalyst that performs well in this hydrolysis is essential. Cobalt-nanoparticles (Co-NPs) supported on magnesium-aluminium layered double hydroxide (LDH) with various mean diameter were synthesized by changing concentration of cobalt-citrate anion (Co-citrate) precursor used for ion exchange with the LDH host. Then the Co-citrate intercalated LDHs were reduced with NaBH4 to form Co-NPs. Evidence of successful intercalation was shown by X-ray diffraction (XRD) and Fourier-Transform Infrared spectroscopy (FT-IR). Transmission Electron Microscope (TEM) and Scanning TEM (STEM) observations revealed that Co-NPs were in metallic state and their mean diameter increased with the concentration of Co-citrate solution. Nitrogen physisorption isotherms showed that the surface structure of LDHs transformed from non-porous to mesoporous after chemical reduction, which indicated that the Co-NPs were formed in the interlayer of LDHs. Catalytic hydrolysis of NaBH4 at 25 degrees C clarified that the catalyst synthesized from 6 mM Co-citrate solution showed the highest H-2 generation rate of 4520 +/- 251 mL min(-1).gCo(-1), indicating the catalyst had the optimum size of Co-NP. This activity could be considered relatively higher compared to unsupported cobalt and many other supported cobalt-base catalysts previously reported. It was also clearly shown that size of Co-NPs supported on LDH could be a significant parameter as it allowed better accessibility of reactants to the active catalyst surface to obtain maximum activity. For this optimum catalyst, the activation energy was evaluated to be 56.9 kJ mol(-1). Although the catalyst was able to achieve almost the same conversion when the catalyst was repeatedly tested five times under the same condition, the catalytic activity decreased gradually. Overall, it could be revealed that Co-NPs supported on LDHs have a huge potential to be used for H-2 energy production.