An official website of the United States government
Abstract The dynamic restructuring of Cu surfaces in electroreduction conditions is of fundamental interest in electrocatalysis. We decode the structural dynamics of a Cu(111) electrode under reduction conditions by joint first‐principles calculations and operando electrochemical scanning tunneling microscopy (ECSTM) experiments. Combining global optimization and grand canonical density functional theory, we unravel the potential‐ and pH‐dependent restructuring of Cu(111) in acidic electrolyte. At reductive potential, Cu(111) is covered by a high density of H atoms and, below a threshold potential, Cu adatoms are formed on the surface in a (4×4) superstructure, a restructuring unfavorable in vacuum. The strong H adsorption is the driving force for the restructuring, itself induced by the electrode potential. On the restructured surface, barriers for hydrogen evolution reaction steps are low. Restructuring in electroreduction conditions creates highly active Cu adatom sites not present on Cu(111).
more »
« less
Structure Sensitivity and Catalyst Restructuring for CO2 Electro-reduction on Copper
Abstract Cu is the most promising metal catalyst for CO2electroreduction (CO2RR) to multi-carbon products, yet the structure sensitivity of the reaction and the stability versus restructuring of the catalyst surface under reaction conditions remain controversial. Here, atomic scale simulations of surface energies and reaction pathway kinetics supported by experimental evidence unveil that CO2RR does not take place on perfect planar Cu(111) and Cu(100) surfaces but rather on steps or kinks. These planar surfaces tend to restructure in reaction conditions to the active stepped surfaces, with the strong binding of CO on defective sites acting as a thermodynamic driving force. Notably, we identify that the square motifs adjacent to defects, not the defects themselves, as the active sites for CO2RR via synergistic effect. We evaluate these mechanisms against experiments of CO2RR on ultra-high vacuum-prepared ultraclean Cu surfaces, uncovering the crucial role of step-edge orientation in steering selectivity. Overall, our study refines the structural sensitivity of CO2RR on Cu at the atomic level, highlights the self-activation mechanism and elucidates the origin of in situ restructuring of Cu surfaces during the reaction.
more »
« less
- Award ID(s):
- 2103116
- PAR ID:
- 10586965
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 16
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
null (Ed.)The selectivity towards a specific C 2+ product, such as ethylene (C 2 H 4 ), is sensitive to the surface structure of copper (Cu) catalysts in carbon dioxide (CO 2 ) electro-reduction. The fundamental understanding of such sensitivity can guide the development of advanced electrocatalysts, although it remains challenging at the atomic level. Here we demonstrated that planar defects, such as stacking faults, could drive the electrocatalysis of CO 2 -to-C 2 H 4 conversion with higher selectivity and productivity than Cu(100) facets in the intermediate potential region (−0.50 ∼ −0.65 V vs. RHE). The unique right bipyramidal Cu nanocrystals containing a combination of (100) facets and a set of parallel planar defects delivered 67% faradaic efficiency (FE) for C 2 H 4 and a partial current density of 217 mA cm −2 at −0.63 V vs. RHE. In contrast, Cu nanocubes with exclusive (100) facets exhibited only 46% FE for C 2 H 4 and a partial current density of 87 mA cm −2 at an identical potential. Both ex situ CO temperature-programmed desorption and in situ Raman spectroscopy analysis implied that the stronger *CO adsorption on planar defect sites facilitates CO generation kinetics, which contributes to a higher surface coverage of *CO and in turn an enhanced reaction rate of C–C coupling towards C 2+ products, especially C 2 H 4 .more » « less
-
Abstract Electrochemical CO2reduction reaction (CO2‐RR) in non‐aqueous electrolytes offers significant advantages over aqueous systems, as it boosts CO2solubility and limits the formation of HCO3−and CO32−anions. Metal–organic frameworks (MOFs) in non‐aqueous CO2‐RR makes an attractive system for CO2capture and conversion. However, the predominantly organic composition of MOFs limits their electrical conductivity and stability in electrocatalysis, where they suffer from electrolytic decomposition. In this work, electrically conductive and stable Zirconium (Zr)‐based porphyrin MOF, specifically PCN‐222, metalated with a single‐atom Cu has been explored, which serves as an efficient single‐atom catalyst (SAC) for CO2‐RR. PCN‐ 222(Cu) demonstrates a substantial enhancement in redox activity due to the synergistic effect of the Zr matrix and the single‐atom Cu site, facilitating complete reduction of C2species under non‐aqueous electrolytic conditions. The current densities achieved (≈100 mA cm−2) are 4–5 times higher than previously reported values for MOFs, with a faradaic efficiency of up to 40% for acetate production, along with other multivariate C2products, which have never been achieved previously in non‐aqueous systems. Characterization using X‐ray and various spectroscopic techniques, reveals critical insights into the role of the Zr matrix and Cu sites in CO2reduction, benchmarking PCN‐222(Cu) for MOF‐based SAC electrocatalysis.more » « less
-
Abstract Hybrid organic‐inorganic heterogeneous catalytic interfaces, where traditional catalytic materials are modified with self‐assembled monolayers (SAMs), create promising features to control a wide range of catalytic processes through the design of dual organic‐inorganic active sites and the induced confinement effect. To provide a fundamental insight, we investigated CO2electroreduction into valuable C2chemicals (CO2RR‐to‐C2) over SAM‐modulated Cu. Our theoretical results show that 1/4 monolayer aminothiolates improve the stability, activity and selectivity of CO2RR‐to‐C2by: (1) decreasing surface energy to suppress surface reconstruction; (2) facilitating CO2activation and C−C coupling through dual organic‐inorganic (i. e., −NH, Cu) active sites; (3) promoting C−C coupling via confinement effects that enlarge the adsorption energy difference between CO*and COH*; (4) inducing local electric fields to Cu surface and changing its dipole moment and polarizability to be in favor of C−C coupling under electrode/electrolyte interfacial electric field.more » « less
-
Dissecting Critical Factors for Electrochemical CO 2 Reduction on Atomically Precise Au NanoclustersAbstract This work investigates the critical factors impacting electrochemical CO2reduction reaction (CO2RR) using atomically precise Au nanoclusters (NCs) as electrocatalysts. First, the influence of size on CO2RR is studied by precisely controlling NC size in the 1–2.5 nm regime. We find that the electrocatalytic CO partial current density increases for smaller NCs, but the CO Faradaic efficiency (FE) is not directly associated with the NC size. This indicates that the surface‐to‐volume ratio, i.e. the population of active sites, is the dominant factor for determining the catalytic activity, but the selectivity is not directly impacted by size. Second, we compare the CO2RR performance of Au38isomers (Au38Q and Au38T) to reveal that structural rearrangement of identical size NCs can lead to significant changes in both CO2RR activity and selectivity. Au38Q shows higher activity and selectivity towards CO than Au38T, and density functional theory (DFT) calculations reveal that the average formation energy of the key *COOH intermediate on the proposed active sites is significantly lower on Au38Q than Au38T. These results demonstrate how the structural isomerism can impact stabilization of reaction intermediates as well as the overall CO2RR performance of identical size Au NCs. Overall, this work provides important structure–property relationships for tailoring the NCs for CO2RR.more » « less
