Noble metallic nanocrystals are used in a wide variety of applications, such as catalysis, batteries, and bio- and chemical sensors. Most of the previous studies focus on the preparation of thermodynamically stable nanocrystals enclosed by low-index facets and discuss their corresponding catalytic properties. Recently, researchers have found that the nanocrystals with high-index facets (HIFs) are of more interest for electrocatalysis. Herein, we review recent key progress in the synthesis of noble metallic nanoparticles enclosed with HIFs and their facet-dependent electrocatalytic behaviors. First, we introduce the concept of HIFs, and establish the correlation between their surface structure and catalytic activity. Then, we discuss various synthetic approaches for controlling the shapes and composition of the nanocrystals enclosed by HIFs. Afterwards, we showcase the enhanced electrocatalytic performance realized by HIF-based nanostructures. Finally, we provide guidance on how to improve the electrocatalysis by engineering HIFs on noble metallic nanocrystals.

Despite various 2H-MoS₂/carbon hybrid nanostructures have been constructed and committed to improve the performance for sodium-ion batteries (SIBs), they still show the limited cycle stability due to the relatively large volumetric expansion during the charge–discharge process. Herein, we report the construction of cobalt-doped few-layered 1T-MoS₂ nanosheets embedded in N, S-doped carbon (CMS/NSC) nanobowls derived from metal-organic framework (MOF) precursor via a simple in situ sulfurization process. This unique hierarchical structure enables the uniformly dispersed Co-doped 1T-MoS₂ nanosheets intimately couple with the highly conductive carbon nanobowls, thus efficiently preventing the aggregation. In particular, the Co-doping plays a crucial role in maintaining the integrity of structure for MoS₂ during cycling tests, confirmed by first-principles calculations. Compared with pristine MoS₂, the volume deformation of Co-doped MoS₂ can be shrunk by a prominent value of 52% during cycling. Furthermore, the few-layered MoS₂ nanosheets with 1T metallic phase endow higher conductivity, and thus can surpass its counterpart 2H semiconducting phase in battery performance. By virtue of the synergistic effect of stable structure, appropriate doping and high conductivity, the resulting CMS/NSC hybrid shows superior rate capability and cycle stability. The capacity of CMS/NSC can still be 235.9 mAh·g^-1 even at 25 A·g^-1, which is 51.3% of the capacity at 0.2 A·g^-1. Moreover, the capacity can still remain 218.6 mAh·g^-1 even over 8, 240 cycles at 5 A·g^-1 with a low decay of 0.0044% per cycle, one of the best performances among the reported MoS₂-based anode materials for SIBs.