Designing
the earth’s abundant and high-performance electrocatalysts,
which possess high stability, excellent electrical conductivity, inherent
active sites, and catalytic activity identical with Pt, is challenging
but crucial for the hydrogen evolution reaction (HER). By first-principles
structure search simulations, we identify a new two-dimensional (2D)
MoPC material with the Janus structure as a promising catalyst. This
novel 2D monolayer has superior stability and metallic conductivity.
Especially, it exhibits a remarkable HER catalytic activity, where
all of the constituent atoms, including Mo, P, and C, can uniformly
act as active sites in view of the near-zero ΔG
H* value. Its active site density counts up to 1.46 ×
1015 site/cm2, larger than that of many reported
materials and even comparable to Pt. The excellent HER catalytic activity
can also be maintained at a very high H coverage with or without external
strain. The MoPC monolayer can produce H2 spontaneously
through the favorable Volmer–Heyrovsky pathway. The detailed
catalytic mechanism behind the high HER activity has been also analyzed.
Our work provides a feasible action for the experimental synthesis
of excellent HER catalysts.