In energy conversion and storage technologies, the design
of highly
efficient trifunctional electrocatalysts integrating with the high
hydrogen evolution reaction (HER) and oxygen evolution/reduction reaction
(OER/ORR) activities is highly desirable. Herein, utilizing first-principles
computations, a novel periodically ordered macropore C30N12S6 monolayer was proposed, and the stability
analysis attests to its good stability. Single transition metal (TM)
atom anchored onto this newly proposed C30N12S6 monolayer to form single-atom catalysts, as achieved
by TM–N2@C30N10S6, among which the Co–N2@C30N10S6 is the most promising multifunctional catalyst toward
HER/OER/ORR with low overpotential of 0.01/0.59/0.3 V; meanwhile,
the Rh–N2@C30N10S6 can be used as a bifunctional OER/ORR catalyst with low overpotential
of 0.37/0.44 V, overmatching the landmark Pt (111) and IrO2/RuO2 catalysts. Particularly, the TM-d orbital in TM@CNS
is remarkably hybridized with the O-p orbital of oxygenated intermediates,
so that the lone electrons initially located at the antibonding orbital
pair up and fill the downward bonding orbital, allowing OH* to be
suitably adsorbed on TM@CNS, enhancing the catalytic performance.
The relevant attributes, such as good stabilities and metallic features,
ensured their applications in ambient conditions. Moreover, multilevel
descriptors were constructed to clarify the origin of activity on
TM@CNS, such as ΔG
OH* (Gibbs free
energy of OH*), εd (d-band center), COHP (crystal
orbital Hamilton population), N
d/N
d + s (number of d/d + s electrons)
and φ (descriptor), among which the filling of outer d-electrons
of TM atom significantly affects the value of ΔG
OH* that can determine the overpotential and, thus, become
a key descriptor.