Highly Efficient Electrocatalytic Hydrogen Production by MoSx Grown on Graphene-Protected 3D Ni Foams
Highly Efficient Electrocatalytic Hydrogen Production by MoSx Grown on Graphene-Protected 3D Ni Foams
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DOI：
10.1002/adma.201202920
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发表时间：
2013-02-06
影响因子：
29.4
通讯作者：
Li, Lain-Jong
中科院分区：
文献类型：
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作者：
Chang, Yung-Huang;Lin, Cheng-Te;Li, Lain-Jong
氢能清洁，是未来替代石油燃料最有前途的候选能源之一。虽然铂等稀有金属在析氢反应（HER）中具有很高的效率，但其稀缺性和高成本阻碍了其大规模应用。[1-6]近年来，纳米尺度的MoS 2和ws2等无机催化剂因其成本低、化学稳定性高、在HERs中具有优异的光催化性能[7-24]和电催化性能而备受关注。如果它们可以用于氢能源设备的开发，它们可能是有用的。为了提高无机催化剂的效率，人们在材料性质的改性、复合催化剂的形成、[26-31]以及纳米结构电极的制备等方面进行了大量的研究。[30-33]最近，为了提高电催化HER效率，已经成功制备了MoS 2/还原氧化石墨烯催化剂复合材料，其中还原氧化石墨烯片具有承载MoS 2的功能，并增强了复合材料的电导率。[31,34]然而，大多数报道的电极材料仍然基于二维（2D）平面结构。为了提高电催化HER效率，有效增加催化剂负载表面积至关重要。因此，对三维电极结构的研究应运而生。用化学气相沉积（CVD）技术在Ni泡沫骨架上合成了三维石墨烯泡沫。[36,37]没有镍骨架支撑的石墨烯泡沫很脆，不能作为承载催化剂的3D电极。3D镍泡沫是一种低成本的导电金属，具有高表面积，非常适合用作载体催化剂的模板，以增加反应位点的数量。[38-40]然而，它在酸性溶液中不稳定，因此不适合电催化HER。在这里，我们报道了生长在Ni泡沫上的石墨烯片提供了强大的保护，并有效地提高了它们在酸中的稳定性。高导电性的3D石墨烯/镍泡沫结构也有效地增加了催化剂负载，从而提高了电催化HER效率。同时，我们在石墨烯保护的Ni泡沫上配制了MoS x （x≥2）催化材料，形成了刚性的3D电催化结构，其中MoS x材料在CVD室中通过不同温度的硫钼酸铵热裂解生长。在0.5 M h2so4溶液中进行了MoS x/石墨烯/3D Ni泡沫的电催化HER。无论是几何面积归一化还是电化学表面积（ESA）归一化，MoS x/石墨烯/3D Ni泡沫的HER电流密度都高于各种平面碳电极（包括碳纸、碳布和石墨烯垫）上的MoS x。材料的x射线光电子能谱（XPS）分析表明，较高的HER效率与非晶态中桥接s2 -或顶端s2 -的存在有关。三维泡沫镍（110ppi，厚度= 1.6 mm）由台湾耐思电池有限公司获得。用CVD法在泡沫镍上生长几层石墨烯的研究在其他地方也有报道简而言之，在CVD生长（气相比ch4: h2 = 15: 100，生长温度1050℃，生长1小时，压力500 mtorr）之前，在1050℃下以100 sccm的h2流还原Ni泡沫。图1a显示了获得的Ni泡沫的扫描电子显微镜（SEM）图像，其中可以清楚地看到亚毫米孔隙和Ni颗粒…
Hydrogen energy is clean and serves as one of the most promising candidates for replacing petroleum fuels in the future. Although the rare metals, such as platinum, have high efficiency in the hydrogen evolution reaction (HER), their scarcity and high cost inhibit large scale applications.[1–6] Recently, inorganic catalysts such as nanometer-scaled MoS 2 and WS 2 have drawn great attention due to their low cost, high chemical stability, and excellent photocatalytic [7–24] and electrocatalytic properties in HERs. They are potentially useful if they can be tailored for the development of hydrogen energy devices. In order to enhance the efficiency of inorganic catalysts, many research efforts have been made toward the modification of material properties,[25] the formation of composite catalysts,[26–31] and the fabrication of the electrodes with nano-architecture.[30–33] Recently, MoS 2/reduced graphene oxide catalyst composites have been successfully made for enhancing the electrocatalytic HER efficiency, where the reduced graphene oxide sheets serve the function of hosting MoS 2 as well as enhancing the conductance of the composites.[31, 34] However, most of the reported electrode materials were still based on two-dimensional (2D) planar structures. To improve the electrocatalytic HER efficiency, it is crucial to effectively increase the surface area for catalyst loading. Hence, the research into three-dimensional (3D) electrode structures is emergent. A three-dimensional graphene foam synthesized on the Ni foam skeleton by chemical vapor deposition (CVD) has been reported.[36, 37] The graphene foam without the support of an Ni skeleton is brittle and is not able to serve as a 3D electrode for hosting catalysts. The 3D Ni foam is a low cost and conductive metal with a high surface area, which is ideal for use as a template to host catalysts for increasing the number of reaction sites.[38–40] However, it suffers from instability in acidic solutions, and thus is not suitable for the electrocatalytic HER. Here, we report that the graphene sheets grown on Ni foams provide robust protection and efficiently increase their stability in acid. The highly conductive 3D graphene/Ni foam structure also effectively increases the catalyst loading, leading to the enhancement in electrocatalytic HER efficiency. Meanwhile, we formulated MoS x (x≥ 2) catalytic materials on grapheneprotected Ni foam to form a rigid 3D electrocatalytic architecture, where the MoS x materials are grown by the thermolysis of ammonium thiomolybdates at different temperatures in a CVD chamber. The electrocatalytic HER of the MoS x/graphene/3D Ni foam was performed in a 0.5 M H2so 4 solution. The HER current density for the MoS x/graphene/3D Ni foam, either normalized by geometrical area or electrochemical surface area (ESA), is higher compared with the MoS x on various planar carbon electrodes including carbon paper, carbon cloth, and graphene mats. X-ray photoelectron spectroscopy (XPS) analysis of the materials reveals that the higher HER efficiency is related to the presence of bridging S 2 2− or apical S 2− in amorphous states.The three-dimensional Ni foam (110 ppi; thickness= 1.6 mm) was obtained from Nexcell battery Co.(Taiwan). The growth of a few layers of graphene on the Ni-foam by CVD has been reported elsewhere.[35] In brief, the Ni foams are reduced with H 2 flow (100 sccm) at 1050 C for half an hour before the CVD growth (gas ratio CH 4: H 2= 15: 100; growth temperature 1050 C for 1 h; pressure 500 mtorr). Figure 1a shows the scanning electron microscopy (SEM) images for the as-obtained Ni foam, where submillimeter pores can be clearly seen and the Ni grains …