In the periodic table, the elements in groups VIB ((n-1)d 5 ns 1 ) and VIIB ((n-1)d 5 ns 2 ) contain adequate HFSO and/or HFDOs, but lower electronegativity (< 1.9)making it difficult for them to bond two atomic hydrogens on their atom's surface. In reality, their electronegativity could be improved by combining them with elements in the group of VA or VIA, such as Nitrogen and Sulfur, which provide a higher electronegativity. Taking Molybdenum (EN is 1.8 and has five HFDOs and one HFSO accessible) as an example, after being compounded with Sulfur (2.5) to form MoS2, there are still two HFDOs exposed on the surface of the Mo atom, which have the potential to link two atomic hydrogens via half-filled orbital interactions. Furthermore, recent research found that MoS2 nanocatalysts delivered an outstanding catalytic behaviour for HER (we just consider the experimental results). Therefore, the other elements in groups VIB and VIIB are expected to be active catalysts, following the same scheme as in the case of Mo conversion to MoS2 with significant catalytic activity towards the HER. Most importantly, it remains a key requirement for at least HFDOs to be accessible on the active site following the improving electronegativity, ensuring that two atomic hydrogens can interact with the catalytic active atom for catalytic HER at lower potentials.