A Ni nanoparticles encapsulated in N-doped carbon catalyst for efficient electroreduction CO2: Identification of active sites for adsorption and activation of CO2 molecules

Pyrrolic N‐Stabilized Monovalent Ni Single‐Atom Electrocatalyst for Efficient CO2 Reduction: Identifying the Role of Pyrrolic–N and Synergistic Electrocatalysis

“…Therefore, these results confirms the pyrrolic N‐C sites in N‐doped graphene favor CO 2 reduction, consistent with previous reports. [ 16,29 ]…”

“…Therefore, these results confirms the pyrrolic N-C sites in N-doped graphene favor CO 2 reduction, consistent with previous reports. [16,29] To clarify the role of NiN 4 sites and defect sites, various active sites were considered (Figure 4b), denoted as NiN 4 defects (defects as the active site), NiN 4 C (C near pyrrolic N as the active site), NiN 4 Ni (Ni as the active site) and NiN 4 N (pyrrolic N as the active site). The free energy change for CO 2 to CO conversion determined by DFT calculations revealed that the formation of COOH* intermediate was the rate-determining step (RDS) on Ni and N sites.…”

“…[27,28] Recently, it was reported that the coexistence of metal nanoparticles (NPs) can substantially alter the electronic structure of the catalysts, thereby considerably influencing the activity and selectivity of CO 2 RR. [16,20,29] Moreover, the presence of intrinsic defects, in combination with MNx sites, can enhance CO production from CO 2 . [22,23] Nevertheless, most of the existing research has been focused on the importance of the MNx domains, and the role of the additional active sites in the synergistic action and their interaction with MNx remain poorly understood.…”

Gadolinium Changes the Local Electron Densities of Nickel 3d Orbitals for Efficient Electrocatalytic CO2 Reduction

“…[18] On the contrary, the graphite stripes disappear and the new Ni (111) crystal planes emerge in CBNNiGd-700 and CBNNi-700, implying that Ni with the relatively small atomic radius is readily incorporated into the graphite lattices of CB, which can generate defect sites. [23] As revealed by the elemental mapping images, Ni atoms agglomerate into nanoparticles encapsulated in the carbon matrixes of CBNNiGd-700 and CBNNi-700, [11] while the relatively uniform dispersion of Gd atoms is accomplished within CBNNiGd-700 and CBNGd-700. [20,24] It is noteworthy that partial Gd atoms in CBNNiGd-700 gather around Ni nanoparticles and that the sizes of Ni nanoparticles in CBNNiGd-700 are significantly smaller than in CBNNi-700.…”

“…[8,9] However, transition metals (TMs) tend to agglomerate into large-size nanoparticles located on support surfaces and/or encapsulated inside carbon layers in preparation processes. [10,11] Nanoparticles with larger sizes are more inclined to catalyze the HER, thus leading to their deteriorating ECR performance. [10,12] It is worth mentioning that nanostructured TMs possess outstanding electrical conductivities, which can facilitate electron transport and therefore contribute to high total current densities.…”