The development of high-activity and low-price cathodic
catalysts
to facilitate the electrochemically sluggish O2 reduction
reaction (ORR) is very important to achieve the commercial application
of fuel cells. Here, we have investigated the electrocatalytic activity
of the two-dimensional single-layer Nb-doped zirconium diselenide
(2D Nb-ZrSe2) toward ORR by employing the dispersion corrected
density functional theory (DFT-D) method. Through our study, we computed
structural properties, electronic properties, and energetics of the
2D Nb-ZrSe2 and ORR intermediates to analyze the electrocatalytic
performance of 2D Nb-ZrSe2. The electronic property calculations
depict that the 2D monolayer ZrSe2 has a large band gap
of 1.48 eV, which is not favorable for the ORR mechanism. After the
doping of Nb, the electronic band gap vanishes, and 2D Nb-ZrSe2 acts as a conductor. We studied both the dissociative and
the associative pathways through which the ORR can proceed to reduce
the oxygen molecule (O2). Our results show that the more
favorable path for O2 reduction on the surface of the 2D
Nb-ZrSe2 is the 4e– associative path.
The detailed ORR mechanisms (both associated and dissociative) have
been explored by computing the changes in Gibbs free energy (ΔG). All of the ORR reaction intermediate steps are thermodynamically
stable and energetically favorable. The free energy profile for the
associative path shows the downhill behavior of the free energy vs
the reaction steps, suggesting that all ORR intermediate structures
are catalytically active for the 4e– associative
path and a high 4e– reduction pathway selectivity.
Therefore, 2D Nb-ZrSe2 is a promising catalyst for the
ORR, which can be used as an alternative ORR catalyst compared to
expensive platinum (Pt).