Electrochemically Fabricated Polypyrrole and MoSx Copolymer Films as a Highly Active Hydrogen Evolution Electrocatalyst
Electrochemically Fabricated Polypyrrole and MoSx Copolymer Films as a Highly Active Hydrogen Evolution Electrocatalyst
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电化学制备的聚吡咯和 MoSx 共聚物薄膜作为高活性析氢电催化剂
DOI：
10.1002/adma.201400265
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发表时间：
2014-06-11
影响因子：
29.4
通讯作者：
Li, Meixian
中科院分区：
文献类型：
--
作者：
Wang, Tanyuan;Zhuo, Junqiao;Li, Meixian
DOI：10.1002/adma. 201400265表面积，以及良好的稳定性。[14]此外，已经证明[MoS 4] 2−和一些其他硫化钼阴离子可以在聚合过程中掺杂到PPy中，[15]这使其成为MoS x的理想载体。在此，我们展示了一个简单的方法来制备聚吡咯/MoS x杂化（PPy/MoS x）薄膜的一步电化学共聚。PPy/MoS x薄膜表现出与商业Pt/C催化剂相当的优异HER性能。在0.1M的NaClO 4溶液中，加入0.5M的吡咯（Py）和2 mM的（NH 4）2 MoS 4，在0.75Vvs.SCE下通过电聚合制备了高活性的PPy/MoS x薄膜。混合溶液在使用前老化过夜。图1a显示了用不同膜改性的电极在0.5M H2SO 4中对HER的催化性能。PPy/MoS x薄膜具有优异的HER性能。可以清楚地看出，析氢发生在相对于RHE的0 V下，这与商业Pt/C的析氢几乎相同。这是迄今为止报道的MoSX基材料在HER电催化方面的最好结果，用（NH 4）2 MoS 4膜修饰的电极也显示出相对高的HER活性，尽管该膜在酸中不稳定，但它不如商业Pt/C催化剂。PPy修饰电极在-0.3V（相对于RHE）的电位下也没有HER活性。以（NH 4）2 MoS 4作为前体，在0.75 V vs. SCE下电沉积的MoS x膜表现出HER的起始电位为-0.24 V vs. RHE，这劣于Hu及其同事[7a]获得的结果，但可以通过沉积电位正得多的事实来解释，用Tafel图进一步研究了PPy/MoS x膜的析氢机理.图1 B是PPy/MoS x修饰电极的塔菲尔图。观察到的Tafel斜率为29 mV dec− 1，远小于通常报道的具有良好HER活性的MoS x（约40 mV dec− 1），[7，9 b]表明PPy/MoS x的HER机制可能是Volmer-Tafel机制，其中Tafel反应作为速率决定步骤，这与Pt上的HER机制相似。对于实际应用，小的塔菲尔斜率是期望的，因为它将有助于HER速率随着增加的过电位而更快地增加。此外，PPy/MoS x的交换电流密度计算为5.6× 10 - 4 A cm-2，在-0.06 V vs. RHE下的催化电流密度为50 mA cm-2，这两个值均显著大于所报道的MoS x基材料[4 b，9，12 a]和NiMo基材料的值。
DOI: 10.1002/adma. 201400265 surface area, as well as good stability.[14] Moreover, It has been demonstrated that [MoS 4] 2− and some other molybdenum sulfide anions can be doped into PPy during the polymerization process,[15] which makes it an ideal carrier for MoS x. Herein, we demonstrate a simple way to fabricate polypyrrole/MoS x hybrid (PPy/MoS x) films by a one-step electrochemical copolymerization. The PPy/MoS x films exhibit an outstanding HER performance that is comparable to that of commercial Pt/C catalysts. The highly active PPy/MoS x films for HER were prepared in 0.1 M NaClO 4 containing 0.5 M pyrrole (Py) and 2 m M (NH 4) 2MoS 4 by electro-polymerization at 0.75 V vs. SCE. The mixed solution was aged overnight before use. Figure 1a displays the catalytic performances of electrodes modified with different films for HER in 0.5 M H2so 4. The PPy/MoS x film exhibits an excellent HER performance. It can clearly be seen that hydrogen evolution occurs at 0 V vs. RHE, which is nearly the same as that of the commercial Pt/C. This is the best result reported to date from MoS x-based materials in electrocatalysis for HER. The electrode modified with an (NH 4) 2MoS 4 film also showed a relatively high HER activity even though the film was not stable in acid, but it is not as good as the commercial Pt/C catalyst. The PPy-modified electrode has no HER activity even at a potential of–0.3 V vs. RHE. The MoS x film that was electrodeposited at 0.75 V vs. SCE with (NH 4) 2MoS 4 as the precursor exhibits an onset potential of–0.24 V vs. RHE for HER, which is inferior to the result obtained by Hu and coworkers [7a] but can be explained by the fact that the deposition potential was much more positive, and its performance was also not as good as that of the (NH 4) 2MoS 4 and PPy/MoS x-modified electrodes.The hydrogen evolution mechanism at the PPy/MoS x films was further investigated by the Tafel plot. Figure 1 b is the Tafel plot of the PPy/MoS x modified electrode. A Tafel slope of 29 mV dec− 1 is observed, which is much smaller than those of commonly reported MoS x with good HER activity (about 40 mV dec− 1),[7, 9b] suggesting that the HER mechanism of PPy/MoS x might be a Volmer–Tafel mechanism with the Tafel reaction as the rate-determining step, which is similar to the HER mechanism on Pt. For practical applications, a small Tafel slope is desirable as it will be helpful for a faster increase of the HER rate with increasing overpotential. Furthermore, the exchange current density of PPy/MoS x was calculated to be 5.6× 10− 4 A cm− 2, and the catalytic current density at–0.06 V vs. RHE is 50 mA cm− 2, which are both significantly larger than those for the reported MoS x-based materials [4b, 9, 12a] and NiMo-based