[论文解读] Self-optimizing layered hydrogen evolution catalyst with high basal-plane activity

Yuanyue Liu, Jingjie Wu+12 more|arXiv (Cornell University)|Aug 19, 2016

MXene and MAX Phase Materials参考文献 46被引用 202

一句话总结

本文识别了 group-5 MX2 催化剂（H-TaS2 和 H-NbS2）具有高活性的基面位点用于氢演化，并展示它们自优化形貌以提升电荷转移和位点可及性，达到与 Pt 相当的性能。

ABSTRACT

Hydrogen is a promising energy carrier and key agent for many industrial chemical processes1. One method for generating hydrogen sustainably is via the hydrogen evolution reaction (HER), in which electrochemical reduction of protons is mediated by an appropriate catalyst-traditionally, an expensive platinum-group metal. Scalable production requires catalyst alternatives that can lower materials or processing costs while retaining the highest possible activity. Strategies have included dilute alloying of Pt2 or employing less expensive transition metal alloys, compounds or heterostructures (e.g., NiMo, metal phosphides, pyrite sulfides, encapsulated metal nanoparticles)3-5. Recently, low-cost, layered transition-metal dichalcogenides (MX2)6 based on molybdenum and tungsten have attracted substantial interest as alternative HER catalysts7-11. These materials have high intrinsic per-site HER activity; however, a significant challenge is the limited density of active sites, which are concentrated at the layer edges.8,10,11. Here we use theory to unravel electronic factors underlying catalytic activity on MX2 surfaces, and leverage the understanding to report group-5 MX2 (H-TaS2 and H-NbS2) electrocatalysts whose performance instead derives from highly active basal-plane sites. Beyond excellent catalytic activity, they are found to exhibit an unusual ability to optimize their morphology for enhanced charge transfer and accessibility of active sites as the HER proceeds. This leads to long cycle life and practical advantages for scalable processing. The resulting performance is comparable to Pt and exceeds all reported MX2 candidates.

研究动机与目标

• 理解决定 MX2 表面在氢演化中的电子因素。
• 证明 group-5 MX2（H-TaS2、H-NbS2）在 HER 中表现出高基底平面活性。
• 显示这些催化剂在运行过程中能够自我优化形貌，以提高电荷转移和位点可及性。
• 评估基底平面活性 MX2 催化剂的长期稳定性及实际加工优势。

提出的方法

• 本研究使用理论分析来识别 MX2 表面上导致 HER 活性的电子因素。
• 对 H-TaS2 和 H-NbS2 进行实验测试，以评估 HER 性能和基底平面活性。
• 在 HER 过程中研究形貌演化，以理解活性位点的自我优化。
• 将催化性能与 Pt 及其他 MX2 候选材料进行比较。
• 评估催化剂的循环寿命和可扩展性潜力。

实验结果

研究问题

• RQ1 MX2 表面的哪些电子因素决定氢演化活性？
• RQ2 group-5 MX2 催化剂能否提供高基底平面活性用于 HER？
• RQ3 这些催化剂在工作过程中是否会自我优化形貌以增强电荷转移和位点可及性？
• RQ4 H-TaS2 和 H-NbS2 的性能与 Pt 及其他 MX2 催化剂相比如何？
• RQ5 基底平面活性 MX2 催化剂的稳定性和可扩展加工的含义是什么？

主要发现

• Group-5 MX2 催化剂（H-TaS2 和 H-NbS2）显示出来自基底平面位点的高 HER 活性。
• 催化剂在 HER 过程中表现出异常的形貌自我优化能力，以改善电荷转移和对活性位点的获得。
• 这些催化剂的性能与 Pt 相当，并且超过了报道的其他 MX2 候选材料。
• 基底平面活性设计提供了较长循环寿命和可扩展加工的实际优势。