Regulating the charge diffusion of two-dimensional cobalt-iron hydroxide/graphene composites for high-rate water oxidation
Regulating the charge diffusion of two-dimensional cobalt-iron hydroxide/graphene composites for high-rate water oxidation
复制标题
调节二维钴铁氢氧化物/石墨烯复合材料的电荷扩散以实现高速水氧化
DOI：
10.1039/d0ta03895d
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发表时间：
2020
影响因子：
11.9
通讯作者：
Wan Li-jun
中科院分区：
文献类型：
--
作者：
Tang Tang;Jiang Wen-Jie;Yuan Lu-Pan;Niu Shuai;Hu Jin-Song;Wan Li-jun
尽管电荷扩散的重要性在许多高性能能量装置中已被认识到，但在用于析氧反应（OER）的电催化剂的设计中，它受到的关注很少，这对于高活性但导电性较低的OER电催化剂（例如具有各向异性导电性的二维金属氢氧化物（MH））特别重要。在此，我们报告了一系列的CoFe氢氧化物纳米片石墨烯（CFH@G）复合材料的精心设计，以证明电荷扩散调节在提高OER活性的MH的重要性。发现位于石墨烯衬底上的几层厚的CFH纳米片提供了有效的面内电荷扩散路径，同时保持衬底表面完全被铺设的纳米片覆盖对于提供足够的活性位点是必要的。过厚或堆叠的纳米片不利于电荷扩散，特别是在大电流输出下。通过调节电荷扩散特性，性能最佳的CFH@ G基材料可以在接近工业条件（6 M KOH和60 °C）下以仅1.507 V的成本提供2000 mA cm−2的稳定OER电流密度。一个实际的水电解槽也展示了在1.694 V下400 mA cm−2的令人印象深刻的电流输出以及17.41%的稳定太阳能转化为氢气的效率。这些发现为电荷扩散在水氧化中的作用提供了新的见解，并可能为开发低成本，稳定和高效的电催化剂开辟一条途径，用于实际的水电解和各种能源设备。
Although the significance of charge diffusion has been recognized in many high-performance energy devices, it has received very less attention in the design of electrocatalysts for the oxygen evolution reaction (OER), which is particularly crucial for highly active but less conductive OER electrocatalysts, such as two-dimensional metal hydroxides (MHs) with anisotropic conductivity. Herein, we report the elaborate design of a series of CoFe hydroxide nanosheets on graphene (CFH@G) composites to demonstrate the importance of charge diffusion regulation in improving the OER activity of MHs. It was discovered that the few-layer-thick CFH nanosheets lying on the graphene substrate provided an effective in-plane charge diffusion pathway, while keeping the substrate surface entirely covered by the laid nanosheets is necessary for providing sufficient active sites. The overly thick or stacked nanosheets are not favourable for charge diffusion, especially at large current outputs. By regulating the charge diffusion properties, the best-performing CFH@G-based material can deliver a steady OER current density of 2000 mA cm−2 at a cost of only 1.507 V under near-industrial conditions (6 M KOH and 60 °C). A practical water electrolyzer also demonstrated an impressive current output of 400 mA cm−2 at 1.694 V as well as a steady solar-to-hydrogen efficiency of 17.41%. These findings provide new insights into the role of charge diffusion in water oxidation and may open up an avenue for developing low-cost, stable and efficient electrocatalysts for practical water electrolysis and diverse energy devices.