Understanding the Origin of Formation and Active Sites for Thiomolybdate [Mo₃S₁₃]^2– Clusters as Hydrogen Evolution Catalyst through the Selective Control of Sulfur Atoms

[Mo₃S₁₃]^2– clusters have become known as one of the most efficient catalysts for the hydrogen evolution reaction (HER) because most of the sulfur (S) atoms in the cluster are exposed, resulting in many active sites. However, the origin of the cluster formation and active S sites in the cluster is unknown, hindering the development of efficient catalysts. Herein, the mechanism of the transition from amorphous MoS₃ to [Mo₃S₁₃]^2– clusters is systematically investigated. In addition, the active S sites have been identified by the selective removal of S atoms via low-temperature heat treatment. In summary, we believe that the clusters grow from amorphous MoS₃ with apical S atoms, and bridging S atoms are the active HER sites in the [Mo₃S₁₃]^2– clusters. The clusters deposited on carbon nanotubes exhibited good electrochemical HER activity with a low onset potential of −96 mV, a Tafel slope of 40 mV/decade, and stability for 1000 cycles

Defect-Assisted Heavily and Substitutionally Boron-Doped Thin Multiwalled Carbon Nanotubes Using High-Temperature Thermal Diffusion

Carbon nanotubes have shown great potential as conductive fillers in various composites, macro-assembled fibers, and transparent conductive films due to their superior electrical conductivity. Here, we present an effective defect engineering strategy for improving the intrinsic electrical conductivity of nanotube assemblies by thermally incorporating a large number of boron atoms into substitutional positions within the hexagonal framework of the tubes. It was confirmed that the defects introduced after vacuum ultraviolet and nitrogen plasma treatments facilitate the incorporation of a large number of boron atoms (ca. 0.496 atomic %) occupying the trigonal sites on the tube sidewalls during the boron doping process, thus eventually increasing the electrical conductivity of the carbon nanotube film. Our approach provides a potential solution for the industrial use of macro-structured nanotube assemblies, where properties, such as high electrical conductance, high transparency, and lightweight, are extremely important