Inspired by our recent finding that Fe_4.5Ni_4.5S₈ rock is a highly active electrocatalyst for HER, we set out to explore the influence of the Fe:Ni ratio on the performance of the catalyst. We herein describe the synthesis of (Fe_xNi_1–x)₉S₈ (x = 0–1) along with a detailed elemental composition analysis. Furthermore, using linear sweep voltammetry, we show that the increase in the iron or nickel content, respectively, lowers the activity of the electrocatalyst toward HER. Electrochemical surface area analysis (ECSA) clearly indicates the highest amount of active sites for a Fe:Ni ratio of 1:1 on the electrode surface pointing at an altered surface composition of iron and nickel for the other materials. Specific metal–metal interactions seem to be of key importance for the high electrocatalytic HER activity, which is supported by DFT calculations of several surface structures using the surface energy as a descriptor of catalytic activity. In addition, we show that a temperature increase leads to a significant decrease of the overpotential and gain in HER activity. Thus, we showcase the necessity to investigate the material structure, composition and reaction conditions when evaluating electrocatalysts.

中文翻译：

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Fe：Ni比和反应温度对（Fe _x Ni _{1– x}）₉ S ₈电催化剂在产氢反应中应用效率的影响

受我们最近的发现启发，Fe _4.5 Ni _4.5 S ₈岩石是HER的高活性电催化剂，我们着手探讨Fe：Ni比对催化剂性能的影响。我们在此描述（Fe _x Ni _{1- x}）₉ S ₈（x= 0–1）以及详细的元素组成分析。此外，使用线性扫描伏安法，我们表明铁或镍含量的增加分别降低了电催化剂对HER的活性。电化学表面积分析（ECSA）清楚地表明，电极表面上的Fe：Ni比为1：1时，活性部位的数量最多，这表明其他材料中铁和镍的表面成分发生了变化。特定的金属间相互作用似乎对于高电催化HER活性至关重要，这由使用表面能作为催化活性描述符的几种表面结构的DFT计算得到支持。此外，我们表明温度升高会导致过电位的显着降低，并导致HER活性增加。因此，