Cu dimer anchored on C₂N monolayer: low-cost and efficient Bi-atom catalyst for CO oxidation

Abstract

By means of density functional theory (DFT) computations, we systemically investigated CO/O2 adsorption and CO oxidation pathways on a bi-atom catalyst, namely, a copper dimer anchored on a C2N monolayer (Cu2@C2N), and we compared it with its monometallic counterpart Cu1@C2N. The Cu dimer could be stably embedded into the porous C2N monolayer. The reactions between the adsorbed O2 and CO via both bi-molecular and tri-molecular Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms were comparably studied, and we found that the bi-atom catalyst Cu2@C2N possessed superior performance toward CO oxidation as compared to the single-atom catalyst Cu1@C2N. Our comparative study suggested that the newly predicted bi-atom catalyst, i.e., a copper dimer anchored on a suitable support is highly active for CO oxidation, which can provide a useful guideline for further developing highly effective and low-cost green nanocatalysts.

1 + 1′ > 2: Heteronuclear Biatom Catalyst Outperforms Its Homonuclear Counterparts for CO Oxidation

“…Previous theoretical studies showed that the single-atom catalyst Fe 1 @C 2 N [54] and biatom catalyst Cu 2 @C 2 N possess good performance for CO oxidation. [48] Thus, we constructed the homonuclear biatom species Fe 2 @C 2 N and the heteronuclear analogue Fe 1 Cu 1 @C 2 N in this study.…”

“…We first examined the energetically most favorable anchoring site of Fe on the C 2 N monolayer, for which three possible anchoring sites [48] were considered. In the lowest energy configuration of Fe 1 @C 2 N, the Fe atom forms three bonds with N atoms, while for the case of Cu 1 @C 2 N, the Cu atom prefers coordinating with two N atoms [48] (Figure S1, Supporting Information). These results are in line with previous theoretical findings.…”

“…For the biatom catalysts examined in this study (homonuclear: Fe 2 @C 2 N and Cu 2 @C 2 N; heteronuclear: Fe 1 Cu 1 @C 2 N), we only considered two configurations (I and II in Figure 1), in which two metal atoms are located in the porous region of C 2 N, since the binding energies at other sites are less favorable. [37,48,50] Both homo-and heteronuclear metal dimers prefer adopting Configuration II, in which two metal atoms coordinate with three N atoms of the C 2 N substrate ( Figure 1; Table S1, Supporting Information). The distance between the two metal atoms in II is slightly longer than that in Configuration I (Table S1) for the three examined biatom catalysts.…”

“…Our previous study revealed that the O 2 dissociation on the Cu 2 @C 2 N is endothermic by 0.27 eV, and the corresponding reaction barrier is 0.50 eV. [48] However, the O 2 dissociations on Fe 2 @C 2 N and Fe 1 Cu 1 @C 2 N monolayers are both barrierlessly, and exothermic by 1.48 and 1.56 eV, respectively ( Figure S5, Supporting Information). These findings are reminiscent of the extremely low O 2 dissociation barriers on the C 2 N monolayer supported transition metal dimers (Co 2 , Ni 2 , and Cu 2 ).…”

“…The cooperation between the support and the metal clusters can promote the O 2 activation and CO oxidation, for example, the activation barriers for O 2 dissociation and CO oxidation on the TiO 2 supported Au and Pd clusters are very low (nearly barrierless). [2][3][4] However, the catalytic activities of the supported metal nanoparticles are size-and on a phthalocyanine sheet exhibit higher catalytic activity for CO 2 reduction; [44][45][46] Compared with their single-atom counterparts, several double transition metal (TM) atoms supported by 2D crystal C 2 N were predicted to have better catalytic performance for oxygen reduction reaction [47] and CO oxidation than their single-atom counterparts; [48] Several other transition metal dimers anchored on C 2 N monolayers were also expected to exhibit high activity for some important chemical reactions, e.g., carbon dioxide electrochemical reduction (Cu 2 @C 2 N), [49] hydrogen evolution reaction (Co 2 @C 2 N, Ni 2 @C 2 N, Cu 2 @ C 2 N, Ru 2 @C 2 N), [50] and nitrogen fixation (Mo 2 @C 2 N, [51] Mn 2 @C 2 N). [52] Note that the metal dimers in the above mentioned biatom catalysts are all homonuclear.…”