Origin of the N-coordinated single-atom Ni sites in heterogeneous electrocatalysts for CO₂ reduction reaction

Abstract

Heterogeneous Ni−N−C single-atom catalysts (SACs) have attracted great research interest regarding their capability in facilitating the CO2 reduction reaction (CO2RR), with CO accounting for the major product. However, the fundamental...

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

“…[ 54 ] The free energy change for COOH* formation on NiN 4 –Ni sites (0.66 eV) was slightly lower than that of NiN 4 –N sites (0.69 eV), suggesting that Ni atoms act as active sites for CO 2 RR (Figure 4d; Table S4, Supporting Information). [ 54 ] It is worth noting that the free energy change for COOH* formation on Ni and N sites is consistent with recent theoretical estimates on pyrrolic N‐coordinated NiN 4 sites, [ 58 ] and is lower than the absorption free energy of COOH* formation on pyridinic N–coordinated NiN 4 sites (>1.6 V). [ 11,15,55,59 ] Although NiN 4 Ni exhibits a slightly stronger binding strength of COOH* than that of NiN 4 N, the free energy path of CO* desorption from the surface of NiN 4 –N (0.38 eV) were thermodynamically more favorable than that on NiN 4 Ni (0.07 eV), suggesting that pyrrolic N favored the CO desorption from the NiN 4 sites.…”

Why heterogeneous single-atom catalysts preferentially produce CO in the electrochemical CO2 reduction reaction

“…Indeed, it has been demonstrated that formation of the chemisorbed CO 2 molecule (*CO 2 ) plays a vital role in the CO 2 RR for numerous catalysts. [32][33][34][35] Nevertheless, physisorbed CO 2 may also contribute to the CO 2 RR. For example, the onestep reduction process in which physisorbed CO 2 reacts with surface-bound *H has been established as the key pathway for formate production.…”

Electrocatalytic CO2 reduction reaction on dual-metal- and nitrogen-doped graphene: coordination environment effect of active sites

“…Furthermore, on the M–N–C catalysts, *COOH can also exhibit the trans -COOH (H-down) adsorption configuration in addition to the cis -COOH (H-up) configuration. 42,43 Thus, we examine the adsorption configurations and adsorption energies of trans -COOH (H-down) on Ni/Fe–N 6 –Gra and Fe/Zn–N 6 –Gra. The calculation results are shown in Fig.…”