Graphene-Supported Tin Single-Atom Catalysts for CO₂ Hydrogenation to HCOOH: A Theoretical Investigation of Performance under Different N Coordination Numbers

Abstract

The effects of the adjustment of the N coordination number in Sn single-atom catalysts toward the activity and selectivity of CO2 hydrogenation to HCOOH are systematically explored via density functional theory calculations. The stability of the studied catalysts was evaluated by formation energy calculations, and the calculated results indicated that Sn-N x C4–x -G (x = 1–4) are structurally stable. Through the discussion of the reaction mechanism, the optimal path of CO2 hydrogenation to HCOOH on all the studied catalysts is via CO2* + H2* → HCOO* + H* → HCOOH*. In addition, they have different speed limit steps. For Sn-N1C3-G and Sn-N2C2-G, the rate-determining step of CO2 to HCOOH is CO2* + H2* → HCOO* + H*, while the rate-determining step of the other two catalysts is HCOO* + H* → HCOOH*. Meanwhile, the order of catalytic activities of Sn-N x C4–x -G is determined to be Sn-N1C3-G > Sn-N2C2-G > Sn-N3C1-G > Sn-N4-G. Furthermore, the origin of the catalytic activities for HCOOH synthesis on Sn-N x C4–x -G is revealed through the calculated p-band center. It demonstrated that the p-band center of the Sn atom is a good descriptor to evaluate the catalytic activity for HCOOH synthesis in the Sn-N x C4–x -G system.

Theoretical Investigation of Graphene Supported Sn–M (M = Fe, Co, Ni, Cu, Zn) Dual-Atom Catalysts for CO2 Hydrogenation to HCOOH

“…The E a value of RDS on it is 0.98 eV, which is lower than that on some reported catalysts, e.g., hydrogen-covered Pd(111) (1.40 eV), 47 Fe x Zr 1−x O 2 (1.59 eV), 48 and TiO 2 supported Ru 2 cluster (1.10 eV). 49 Furthermore, the activity of SnZnN 6 /G is superior to that of Sn-N 1 C 3 -G (1.10 eV), 27 the most active catalyst in the SnNC system, and it indicates that the activity of SnZnN 6 /G is superior to that of Sn SAC. The above analysis demonstrates that constructing Sn−M DACs by combining Sn with suitable TMs can effectively modulate catalytic performance.…”

“…21−26 Liang et al have proved that SnNC SACs have high activity and selectivity for CO 2 hydrogenation to HCOOH. 27 However, due to their single active site, SACs have difficulty breaking the unfavorable linear scaling relationship between intermediates adsorption in complex reactions involving multiple intermediates. 28,29 As an extension of SACs, dual-atom catalysts (DACs) provide a possibility to solve this problem, and they have aroused much interest among researchers.…”

“…Apart from the well-researched transition metal-based materials, the main-group metals (In, Sn, Bi, etc.) have also shown promising catalytic activity for converting CO 2 to HCOOH recently. − In particular, Sn-based catalysts stand out from many main-group metals materials due to their environmental-friendly and cheap characteristics and high selectivity for formate products. − Single-atom catalysts (SACs) have the maximum atom utilization, active sites with adjustable coordination environment, and unique electronic structure, which have attracted more and more attention in the field of catalysis. − Liang et al have proved that SnNC SACs have high activity and selectivity for CO 2 hydrogenation to HCOOH . However, due to their single active site, SACs have difficulty breaking the unfavorable linear scaling relationship between intermediates adsorption in complex reactions involving multiple intermediates. , As an extension of SACs, dual-atom catalysts (DACs) provide a possibility to solve this problem, and they have aroused much interest among researchers. , Ouyang et al have reported that the linear relationship could be broken by forming DACs to achieve efficient CO 2 reduction reactions via first-principles calculations .…”

Theoretical Insights on ORR Activity of Sn-N-C Single-Atom Catalysts

“…Notably, Sn-based SACs have demonstrated remarkable catalytic activity in various chemical reactions [ 6 ]. For instance, Liang et al conducted a systematic study on the effects of altering the nitrogen coordination number in Sn single-atom catalysts (SACs) to investigate the activity and selectivity of CO 2 hydrogenation to formic acid (HCOOH) [ 7 ]. Tang et al conducted a comprehensive theoretical investigation on the performance of Sn single-atom catalysts (SACs) in the oxygen reduction reaction (ORR) using an associative four-electron mechanism [ 8 ].…”

Rare Earth Metal Anchored into Nitrogen-Doped Graphene for CO2 Electrocatalytic Reduction to C1 Products

“…Generally, graphene will have some vacancies in the preparation process, so it is regarded as a suitable carrier for anchoring metal atoms to facilitate catalysis of diverse reactions. , Simultaneously, by adjusting the coordination atoms (N, O, S, P, etc.) to modify the local electronic structure of the active site, the catalytic performance of SACs can be improved to a certain extent. − Moreover, it has been proved that the N atom with large electronegativity is an effective dopant to adjust the catalytic activity of SACs. − REMs anchored into N-doped graphene have been developed and have demonstrated excellent performances in a wide range of catalytic processes. , For example, Li et al synthesized dispersed Ce atoms catalyst anchored into N-doped graphene, which exhibited remarkable activity in the oxygen reduction reaction . Liu et al also successfully synthesized Y/Sc SACs on N-graphene, confirming that it showed excellent catalytic activity in nitrogen reduction reaction and CO 2 RR .…”