Tuning the structure, morphology, and electronic state is of great significance to achieve highly efficient hydrogen evolution reaction (HER) electrocatalysts. In this work, we originally develop a silk-cocoon structured S-rich cobalt polysulfide (CoS_x, x ≈ 3.9) catalyst with extremely high HER activity through a facile hydrothermal process. The formation mechanism of the silk-cocoon structured CoS_x has been systematically studied and the key factors in the formation of this structure are discussed. Such a nanostructured catalyst has hollow spheres that are interwoven by numerous sub-10 nm nanofibers to form into a three-dimensional conductive network by connection of micrometer long nanofibers. The silk-cocoon structured CoS_x shows excellent HER activity with an onset potential of 0 V vs. a reversible hydrogen electrode and a Tafel slope of 41 mV dec⁻¹. The activity is much higher than that of the reported metal sulfide materials and is even comparable to commercial Pt/C. Moreover, the overpotential to yield a current density of 10 mA cm⁻² is only 42 mV. We ascribe the high HER activity to the S-rich sites and the conductive silk-cocoon structure, which can benefit the charge transfer of the material. Thus, this work provides a guiding strategy for synthesis of nanostructured transition metal polysulfides with enhanced HER catalytic performance.

中文翻译：

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易于合成的富丝茧S钴多硫化物，可作为制氢反应的有效催化剂†

调整结构，形态和电子状态对于实现高效的析氢反应（HER）电催化剂具有重要意义。在这项工作中，我们原来制定了丝茧结构化富S-钴硫化物（CoS的_X，X ≈3.9）催化剂具有非常高的她度过一个浅显的水热法活动。对蚕茧结构化CoS _x的形成机理进行了系统的研究，并讨论了形成该结构的关键因素。这样的纳米结构催化剂具有空心球，空心球被许多10nm以下的纳米纤维交织，通过连接微米长的纳米纤维而形成三维导电网络。丝茧结构的CoS _x相对于可逆的氢电极，它具有出色的HER活性，起始电势为0 V ，Tafel斜率为41 mV dec ^-1。活性远高于已报道的金属硫化物材料，甚至可以与市售Pt / C相媲美。而且，产生10mA cm ^-2的电流密度的过电势仅为42mV。我们将高HER活性归因于富含S的位点和导电的蚕茧结构，这可以有利于材料的电荷转移。因此，这项工作为合成具有增强的HER催化性能的纳米结构过渡金属多硫化物提供了指导策略。