Constructing carbon-cohered high-index (222) faceted tantalum carbide nanocrystals as a robust hydrogen evolution catalyst. (June 2017)

• Record Type: Journal Article
• Authors: Kou, Zongkui; Xi, Kai; Pu, Zonghua; Mu, Shichun
• Is Part Of: Nano energy. Volume 36(2017:Jun.)
• Page Start: 374
• Page End: 380
• Publication Date: 2017-06
• Subjects: High-index facets -- Tantalum carbide -- Chlorination -- Hydrogen evolution; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2017.04.057
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: The electrocatalysis of nanoscale group V metal carbides (e.g. TaC) has almost received far less attentions owing to lack of active sites. Our theoretical calculations show that high-index (222) facets of TaC are dramatically more active than its other facets towards hydrogen evolution reaction (HER). However, the easy evolution of exposed high-index (222) facets causes a big challenge in fabrication. Here, to obtain the carbon-cohered high-index (222) faceted tantalum carbide nanocrystals (TaC NCs@C), we first develop a novel chlorine-assisted "micro-cutting-fragmentation" technique by incomplete chlorination towards bulk TaC. Interestingly, benefiting from transition zones between in situ formed carbon layers and (222) facets, the evolution of high-index (222) facets with high surface energy can be prevented during the preparation and electrochemical reaction. When evaluated as a HER catalyst, TaC NCs@C presents a low overpotential of ~146 mV at 10 mA cm -2, a large exchange current density of 9.69×10 -2 mA cm -2 and outstanding long-term cycling performance. To the best of our knowledge, this HER performance is far preferable to that of the reported group V metal carbides-based catalysts. In the light of the highly generic nature, the methodology developed in this study can be widely applied to produce other in situ carbon armored high-index faceted metal carbide nanocrystals. Graphical abstract: High-index (222) faceted tantalum carbide nanocrystals cohered by in situ amorphous carbon are one-step fabricated based on a novel "micro-cutting-fragmentation" technique by incomplete chlorination towards bulk TaC. Consistent with theoretical calculations, the new produced catalyst presents extraordinary HER activity which surpasses all reported group V metal carbides-based catalysts. That can be attributed to abundant active sites on the exposed high-index (222) facets. Highlights: High index (222) faceted TaC nanocrystals are first created. A subtle micro-cutting-fragmentation technique is newly developed. The novel catalyst exhibits much higher HER activity than that of bulk TaC. It has become one of the most competitive transition metal carbides-based HER catalyst. DFT calculations are used to clarify the role of (222) facet.