We synthesized the trimetallic catalyst (Cu-Sb-Pb) using a co-reduction method in pure ethanol solution instead of deionized water (see Methods). This eliminated the need for exotic complexants such as citric acid since Sb3+ would not precipitate in nonaqueous solvents such as ethanol10,11, thus avoiding potential contaminants. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurements revealed that the Sb and Pd contents in the as-prepared sample were ca. 5.0 and 3.0 at%, respectively. X-ray photoelectron spectroscopy (XPS) also demonstrated the successful incorporation of two metal components, Pd and Sb, into this trimetallic catalyst (Supplementary Fig. 2). The X-ray diffraction pattern of the as-synthesized catalyst showed a pure Cu crystal structure (PDF 04-0836, Supplementary Fig. 3), ruling out the formation of either Sb or Pd nanoparticles and verifying that the bulk phase alloy remained unoxidized. The morphology of the sample was characterized by transmission electron microscopy (TEM) with sizes ranging from 10 to 20 nm (Supplementary Fig. 4). The atomic structure of the Cu-Sb-Pb catalyst was then investigated by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) combined with energy-dispersive X-ray spectroscopy (EDS). Figure 1a clearly reveals the atomic dispersion of Pd/Sb atoms across the Cu matrix, which are marked by yellow circles and magnified into a three-dimensional structure. Then, STEM-EDS mapping further confirmed an even distribution of Sb and Pd in the Cu base without noticeable aggregation. Additionally, large-scale EDS mapping also precluded the existence of Sb or Pd particles (Supplementary Fig. 5). The above results, taken together, demonstrate the successful synthesis of trimetallic alloys, namely, the Cu92Sb5Pd3 catalyst.Fig. 1: Structural characterization of the Cu92Sb5Pd3 catalyst.a HAADF-STEM image and STEM-EDS mapping of Cu, Sb and Pd of the Cu92Sb5Pd3 catalyst. The yellow circles highlight single Sb/Pd atoms, one of which was magnified into a 3D structure. Note that since the atomic numbers of Sb and Pd are quite close, HAADF-STEM failed to differentiate them. b, c Ex situ EXAFS spectra at the Sb and Pd K-edge of the Cu92Sb5Pd3 catalyst, respectively. The spectra of Sb and Pd foil are shown as references. d EXAFS wavelet transforms for the Sb and Pd K-edge of the Cu92Sb5Pd3 catalyst. Sb and Pd foil are shown as references. e Operando Cu K-edge XAFS spectra of the Cu92Sb5Pd3 catalyst under applied potentials during the CO2RR. Cu foil is shown as a reference. All potentials were calibrated to the RHE scale.To better comprehend how Sb and Pd atoms are arranged in the Cu base, we performed extended X-ray absorption fine structure (EXAFS) measurements to examine their coordination environment. Figure 1b, c show the EXAFS curves of Sb and Pd, respectively, for Cu92Sb5Pd3. The peak at ~ 2.30 Å was attributed to the Sb-Cu bond, while no Sb-Sb bonds were detected, confirming the singly dispersed Sb atoms in the alloy (Fig. 1b). The wavelet transform (WT) of Sb K-edge EXAFS supports this finding, which displays only one intensity maximum at ~ 8.6 Å−1 corresponding to Sb-Cu coordination (Fig. 1d and Supplementary Table 1). Similarly, the curve for Pd exhibits a peak at ~ 2.27 Å, which corresponds to the Pd-Cu bond, and no Pd-Pd were observed (Fig. 1c). This suggests that Pd atoms are also dispersed as single sites in the alloy. The WT of Pd K-edge EXAFS corroborates this result by showing an intensity maximum at ~ 9.6 Å−1 corresponding to Pd-Cu coordination (Fig. 1d and Supplementary Table 2). Neither Sb-O nor Pd-O bonds were detected in the EXAFS profiles, implying that Cu92Sb5Pd3 is not oxidized. This is also confirmed by the Cu K-edge EXAFS and WT results (Supplementary Figs. 6 and 7), which show only Cu-Cu bonds (~ 2.24 Å in the EXAFS profile) and no evidence of copper oxides. Of note, we did not observe the formation of the Sb-Pd motif, implying that the Sb and Pd dopants are highly diluted as isolated atoms by the Cu base. Based on these results, we can conclude that we successfully synthesized a trimetallic single-atom alloy, Cu92Sb5Pd3.To investigate the electronic interaction between the Cu base and the dopants under reaction conditions, we conducted an operando X-ray absorption spectroscopy (XAS) study. Note that due to the low contents and therefore weak signal intensities, we, unfortunately, failed to detect the Sb and Pd signals in situ. However, operando Cu K-edge X-ray absorption fine structure (XAFS) showed that the Cu matrix of Cu92Sb5Pd3 maintained a higher oxidation state of Cu at the open circuit potential (OCP), probably caused by oxidation during the electrode preparation process, which could be immediately reduced to a nearly metallic state under cathodic potentials. Very interesting, the operando XAS analysis provides unambiguous experimental evidence that the Cu matrix’s electronic state of Cu92Sb5Pd3 presented partially electron-deficient states during the whole reaction (Fig. 1e and Supplementary Fig. 8), which could be ascribed to the charge redistribution between Sb/Pd additions and the Cu matrix. This observation implies that such a Cu92Sb5Pd3 single-atom alloy with a different electronic structure will mediate the CO2 conversion in a unique way compared to pure Cu.To evaluate the CO2RR catalytic performance of Cu92Sb5Pd3, we performed CO2 electrolysis in a standard three-electrode flow cell system with 0.5 M KHCO3 as the electrolyte (see Methods). Gas products were analysed using gas chromatography (GC), whereas ion chromatography (IC) and nuclear magnetic resonance (NMR) spectroscopy were employed for liquid product quantification. The NMR results showed that formate was the only solution-phase product (Fig. 2a and Supplementary Fig. 9), while the GC analysis detected CO and H2 as major gas-phase products (Supplementary Fig. 10). As shown in Fig. 2a, b, a high plateau of FECO over 95% was retained across a broad potential range from −0.78 ( ± 0.02) to −1.09 ( ± 0.03) V vs. RHE, whereas the competitive HER was suppressed to below 3%. The maximal FECO reached up to 100% (±1.5%) with a CO partial current density (jCO) of −402 mA cm−2 at approximately −0.93 ( ± 0.03) V vs. RHE. Notably, at approximately −1.19 ( ± 0.04) V vs. RHE, Cu92Sb5Pd3 delivered a high jCO exceeding −700 mA cm−2 while still maintaining a CO selectivity of 90% (±2.8%). Moreover, 85% (±3.8%) FECO could be sustained when the current density increased to −1000 mA cm−2. To demonstrate that the exclusive selectivity for CO was due to the synergistic effect of both Pd and Sb single-atom components in Cu, binary single-atom alloy systems, namely, Cu95Sb5 and Cu97Pd3, and pure Cu nanoparticles were included for comparison using a similar method for Cu92Sb5Pd3 (Supplementary Figs. 11–15 and Supplementary Table 3). In contrast to Cu92Sb5Pd3, the CO2RR catalytic performances of Cu95Sb5, Cu97Pd3, and pristine Cu were much less satisfying. Compared with pristine Cu, alloying either Sb or Pd single atoms could promote the selectivity and activity of CO to some extent (Fig. 2a, b and Supplementary Fig. 16). However, some C2+ products, such as C2H4 and alcohols, were also noticeable, especially under high production rates. In addition, the HER became dominant under high overpotentials, leading to a retarded increase in jCO. To account for the influence of different electrochemically active surface area (ECSA) of the four catalysts, we normalized jCO by ECSA to compare their intrinsic activities (Fig. 2c and Supplementary Fig. 17). The results showed that surface normalization exerts only a negligible effect on the performance trend. Additionally, we also increased the contents of Sb and Pd in the bimetallic counterparts, namely, Cu92Sb8 and Cu92Pd8 (Supplementary Table 3), to verify whether simply enhancing one single-atom composition could achieve such performance. The results in Supplementary Fig. 18 show that Cu92Sb8 produced a large amount of formate even under modest current densities, while Cu92Pd8 failed to suppress C-C coupling on the Cu matrix. Hence, we concluded that merely adding one single-atom component to the Cu base was insufficient, especially under a high current density, to achieve a high selectivity toward CO. The stunning catalytic performance of the trimetallic single-atom alloy Cu92Sb5Pd3 stemmed from the concurrent presence of both Pd and Sb single-atom additions.Fig. 2: CO2RR performance over Cu92Sb5Pd3 and control samples (Cu, Cu95Sb5 and Cu97Pd3).a FEs of all CO2RR products at different current densities for Cu92Sb5Pd3, Cu95Sb5 and Cu97Pd3. b, c jCO-V and ECSA normalized jCO-V curves of four as-synthesized catalysts. The error bars in a–c correspond to the standard deviation of three independent measurements with 0.5 M KHCO3 as the electrolyte. d CV investigations of the hydrogen desorption of the Cu and Cu92Sb5Pd3 catalysts. e In situ DEMS measurements of four different catalysts in the CO2RR. f jCO-V curves of state-of-the-art noble metal catalysts in flow cell systems during the CO2RR compared with the Cu92Sb5Pd3 catalyst. Catalyst references reproduced from Ag-NOLI (1 M KHCO3)50, Ag/MPL (0.1 M KHCO3)51, 3D AuAg (1 M KHCO3)52, MWNT/PyPBI/Au (2 M KHCO3)53, MWNT/PyPBI/Au-DMAc (1 M KCl)54, Ag-EPy-2 (0.1 M KHCO3)55, CD-Ag-PTFE (1 M KHCO3)56, Ag NPs (2 M KHCO3)57, Au-C-P-0.5 (1 M KHCO3)58 and AgNF/GDE (1 M KCl)59. All potentials were calibrated to the RHE scale. g Stability test at −100 mA cm−2 current density in MEA for 22 days (528 h) without iR corrections to the voltage.To decipher the effect of alloying both Sb and Pd single atoms on the HER, a major side reaction of the CO2RR, we conducted cyclic voltammetry (CV) investigations to monitor hydrogen desorption peaks in the double layer region. Figure 2d shows that Cu92Sb5Pd3 exhibited no hydrogen desorption peaks, unlike pristine Cu, which had prominent peaks indicating abundant hydrogen from the HER. This confirmed the suppression of the HER by introducing Pd and Sb atoms. We further investigated the possible reaction mechanism for CO2-to-CO conversion on four different electrocatalysts using kinetic analysis. Tafel analysis was conducted to examine the rate determining steps (RDSs) involved in CO2RR. The Tafel result plotted in Supplementary Fig. 19 revealed a faster kinetic process of CO formation on Cu92Sb5Pd3 (138.7 mV dec−1) than on the other three counterparts (Cu as 237.6 mV dec−1, Cu97Pd3 as 211.2 mV dec−1 and Cu95Sb5 as 199.8 mV dec−1), indicating an accelerated electron transfer process12,13. When increasing the overpotential, a faster increase in the CO2 reduction rate occurred on Cu92Sb5Pd3, highlighting the critical role of two single-atom metal components in boosting CO2-to-CO conversion. Moreover, the Tafel slope of 138.7 mV dec−1 for Cu92Sb5Pd3 suggested that the first electron transfer step of *CO2 was the RDS14. Note that the deviation from a theoretical value of 118 mV dec−1 (Supplementary Table 4) was likely due to more complicated electron transfer and electrochemical processes in real reactions15. Furthermore, the comparison of in situ differential electrochemical mass spectrometry (DEMS) results verified the promoted CO2 reduction rate on Cu92Sb5Pd3. Figure 2e shows that Cu92Sb5Pd3 had a lower onset potential for CO generation but a higher onset potential for C2H4 formation than the other three, underlying its merit of inhibiting CO*-CO* coupling to C2+ products16. The obvious differences in onset potentials also revealed a successful modulation of Cu via alloying with two other single-atom metal components.To elucidate the role of the two single-atom components in enhancing the CO2RR, we benchmarked our catalyst against state-of-the-art noble metal catalysts in neutral electrolytes, e.g., KHCO3 or KCl. As illustrated in Fig. 2f and Supplementary Fig. 20, these noble metal catalysts exhibit similar CO onset potentials, but their current densities are far from meeting the requirements for industrial applications. At more negative potentials, their faradic efficiencies and partial current densities for CO plummet rapidly due to overwhelming HER17,18. In comparison, Cu92Sb5Pd3 is on par with or even surpasses noble metals in terms of selectivity but also attained an extremely high current density that outshines most noble metal catalysts. To evaluate the durability of Cu92Sb5Pd3 under realistic conditions, a long-term stability test was conducted in a membrane electrode assembly (MEA) at a current density of −100 mA cm−2. Strikingly, the results show that the FECO was maintained above 95% for 22 days without an evident voltage drop (Fig. 2g). In particular, the robust durability of Cu92Sb5Pd3 even outperforms previously reported state-of-the-art noble metal catalysts (Supplementary Table 5). The outstanding durability was supposed to be derived from the increased mixed entropy of the trimetallic system that improved the stability by suppressing atom aggregation. Post-catalysis analyses, combining HAADF-STEM, STEM-EDS, and large-scale EDS screening (Supplementary Figs. 21-23), all demonstrated well-dispersed Sb/Pd atoms on the Cu matrix after CO2RR, further attesting the robust durability of Cu92Sb5Pd3. In comparison, the bimetallic counterpart, Cu95Sb5, which showcased a considerable improvement in CO generation, failed to maintain the SAA structure after a large current density electrolysis. The HAADF-STEM and EDS figures in Supplementary Fig. 24 exhibit the segregation of the Sb composition after the CO2RR over −800 mA cm−2, demonstrating the inferior stability of the bimetallic counterparts. Such a phenomenon confirmed our previous assumption that an increase in the mixing entropy of the system will lead to a lower ΔG and improved stability. Our theoretical simulations (Supplementary Fig. 25) revealed surface energies of 0.22, 0.21, 0.19, and 0.18 eV per atom for Cu, Cu97Pd3, Cu95Sb5, and Cu92Sb5Pd3, respectively, further confirming the improved stability of the Cu92Sb5Pd3 SAA catalyst by co-doping Sb and Pd on a Cu base.To gain a better understanding of the CO2-to-CO pathway, we conducted in situ Raman spectroscopy, a sensitive technique for detecting CO* intermediates19, to monitor the evolution of reactive intermediates. Figure 3a, b show the in situ Raman spectra acquired for four samples during a negative-going potential sweep from 0 to −1.2 V vs. RHE. Upon applying cathodic potentials, noticeable Raman peaks emerged from 2000 to 2100 cm−1 for the three control samples. The high-frequency bands appearing at ~ 2080 cm−1 were attributed to CO* on step sites of the Cu base, whereas the low-frequency bands at ~ 2045 cm−1 correspond to CO* on terrace sites20. The emergence of two peak positions indicated a higher surface coverage of absorbed *CO on the control samples. We also observed redshifts of these peaks at more negative potentials due to the Stark tuning effect for those three samples. In contrast, on Cu92Sb5Pd3, only a weak peak appeared at ~ 2080 cm−1 under a relatively negative potential, indicating a lower coverage of CO* intermediates. Moreover, we detected a peak at ~ 360 cm−1 associated with Cu-CO stretching21,22, which was more pronounced on the three control samples than on Cu92Sb5Pd3. These results clearly demonstrate a higher concentration of CO* intermediates on Cu, Cu95Sb5 and Cu97Pd3, which reasonably explains their higher productivities toward C2+ products such as C2H4. We further explored the adsorption behavior of the chemical intermediates at the active sites by performing in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) from 0 to −1.0 V vs. RHE. The in situ ATR-SEIRAS spectra in Supplementary Fig. 26 show similar bands related to surface-bond CO* at 2000–2100 cm−1 among the four samples23. With a negatively sweeping potential, all CO* band frequencies redshifted due to the Stark effect24. Notably, at −1.0 V vs. RHE, the CO* peak almost vanished on Cu92Sb5Pd3 but still remained on other samples, indicating an easier desorption of CO* intermediates from the Cu92Sb5Pd3 catalyst surface to form gaseous CO25.Fig. 3: Mechanistic studies of the electrochemical CO2-to-CO conversion on Cu92Sb5Pd3.a, b In situ Raman spectra of four different catalysts at various potentials (reference to RHE). c CO-DRIFTS measurements of four different catalysts. d Normalized CO peak ratio obtained from c as a function of time. An illustration of the CO-DRIFTS mechanism is inserted at the top. e SVBS measurements of four as-synthesized catalysts.To complement the in situ spectroscopic evidence from Raman and ATR-SEIRAS spectra, we also employed CO-diffuse reflectance infrared Fourier transform spectroscopy (CO-DRIFTS) measurements to support our results. Generally, the adsorption/desorption rate of CO* intermediates depends on their binding strength on different catalysts. A strong binding strength promotes CO*-CO* coupling to C2+ products26, while facile binding inhibits the formation of coupling products. Hence, a slow adsorption/desorption rate enhances the possibility of coupling between CO* intermediates, leading to the generation of multicarbon products. Conversely, a fast adsorption/desorption rate favors the formation of gaseous CO since the coverage of CO* intermediates is low. To measure the desorption rate of CO* intermediates on four catalysts, we performed a series of CO-DRIFTS measurements. All samples were first exposed to gaseous CO until saturation and then swept with Ar to measure the desorption rates of preadsorbed CO (COad). During the desorption process, the main peaks at ~ 2100 cm−1 in Fig. 3c were attributed to COad on Cu species27,28,29, which reinforced the fact that Cu sites served as the absorption sites for CO in the four samples, consistent with the in situ spectroscopy results. After normalizing by peak area to the same range, Fig. 3d shows that the desorption rates of COad among the four samples rank as follows: rCO (Cu92Sb5Pd3)> rCO (Cu95Sb5)> rCO (Cu97Pd3)> rCO (Cu). Therefore, it is rationalized that CO* intermediates are most likely and easiest to desorb on Cu92Sb5Pd3 compared to the other three, which explains the near-unity selectivity of Cu92Sb5Pd3 toward CO rather than C2+ products.In this work, we sought to coordinatively tune the electronic structure of Cu by alloying two distinct single atoms, steering it towards selective CO production with enhanced activity and stability. To corroborate our hypothesis with direct experimental evidence, we probed the electronic structure of the catalysts by synchrotron valance band spectra (SVBS) measurements30,31, as shown in Fig. 3e. These spectra reflect the density of state (DOS)32 and showed that the 3d bands of Cu in different samples varied with the composition of different single-atom metals. After adding Pd and Sb to the Cu base individually, the d-band center of Cu shifted downwards from 2.73 eV to 2.80 eV and 2.83 eV, respectively. Upon adding both single-atom metals simultaneously, the d -band center further shifted to 2.87 eV. This trend of the d-band centers indicated a logical change in the electronic structure, as we predesigned, which was also in accordance with our follow-up density functional theory (DFT) calculated deductions (Supplementary Fig. 27). It is generally accepted that the variation in d-band centers correlates with different adsorption energies for intermediates during the CO2RR4,5,9. The lowest d-band center of Cu92Sb5Pd3 forecasted a fairly weak binding strength of CO* intermediates to the catalyst surface, which facilitated their desorption to form gaseous CO.To gain further insights into the origin of the stunning CO evolution performance of Cu92Sb5Pd3, we performed theoretical simulations to investigate the effect of Pd and Sb dopants. As discussed previously33, Cu (211) surface is more active for the CO2RR to CO than Cu (111) and Cu (100). For copper-based single-atom alloy catalysts, their simulation performance on step surface is in good agreement with experimental results4,5. Thus, the Cu (211) surface model was finally chosen. Three models with different Pd doping positions were constructed, namely, Cu92Sb5Pd3 (211), Cu92Sb5Pd3 (211)−1 and Cu92Sb5Pd3 (211)−2 (Supplementary Fig. 28). As shown in Fig. 4a, the adsorption energies of CO* on Cu92Sb5Pd3 (211)−1 and Cu92Sb5Pd3 (211)−2 are weaker than those on Cu (211), Cu97Pd3 (211) and Cu95Sb5 (211), where CO* was adsorbed at the top site on the Cu atom adjacent to the Sb and Pd atoms. Similarly, the Gad CO* on Cu (211), Cu97Pd3 (211) and Cu95Sb5 (211) were all obtained with CO* adsorbed at the top sites on Cu atoms (Supplementary Fig. 29). However, when CO* was adsorbed at the bridge site between Cu and Pd atoms on Cu92Sb5Pd3 (211), the adsorption energy of CO* on Cu92Sb5Pd3 (211) was stronger than that on Cu (211), Cu97Pd3 (211) or Cu95Sb5 (211). Based on the experimental characterization results, where weakened CO* adsorption was found on Cu92Sb5Pd3 relative to either Cu or Cu95Sb5, the bridge Cu site on Cu92Sb5Pd3 (211) should not be the predominant active site. Hence, Cu92Sb5Pd3 (211)−1 and Cu92Sb5Pd3 (211)−2 were chosen for the subsequent calculation and analysis. To further excavate the difference between Cu92Sb5Pd3 (211)−1 and Cu92Sb5Pd3 (211)−2, the electrochemical barriers of the CO2RR to CO over these two structures were calculated. The electrochemical barriers were first calculated on the basis of the “charge extrapolation” method34,35 within the capacitor model36. The amount of electron transfer (Δq) from the water layer to the electrode is linearly correlated with the relative work function (Φ) at the initial states (IS), transition states (TS), and final states (FS) (Supplementary Figs. 30–33). We chose a cathodic potential of −0.93 V vs. RHE for further theoretical simulations, at which the highest FECO of 100% (±1.5%) could be reached at −402 mA cm−2 on Cu92Sb5Pd3. Figure 4b, c show that at −0.93 V vs. RHE, the kinetic barrier of CO formation on Cu92Sb5Pd3 (211)−2 is lower than that on Cu92Sb5Pd3 (211)−1. In addition, Cu92Sb5Pd3 (211)−2 shows lower barriers for the hydrogenation of CO2 and COOH* than Cu (211), Cu97Pd3 (211) and Cu95Sb5 (211) (Supplementary Fig. 34). Besides, microkinetic modelling over Cu92Sb5Pd3 (211)−1 and Cu92Sb5Pd3 (211)−2 was also conducted at −0.93 V vs. RHE (Fig. 4d). The theoretical rates of CO production on Cu92Sb5Pd3 (211)−1 and Cu92Sb5Pd3 (211)−2 are both higher than those on Cu (211), Cu97Pd3 (211) and Cu95Sb5 (211), among which Cu92Sb5Pd3 (211)−2 shows the highest theoretical activity. Taken together, Cu92Sb5Pd3 (211)−2 is supposed to be the major active structure, while Cu92Sb5Pd3 (211)−1 tends to be suboptimal. The barriers and reaction free energies of the main and side reactions are summarized in Supplementary Tables 6 and 7. The TOFs of the different products for CO2RR and HER on Cu97Pd3 (211), Cu95Sb5 (211), Cu92Sb5Pd3 (211)−1 and Cu92Sb5Pd3 (211)−2 surfaces at −0.93 V vs. RHE were additionally calculated and listed in Supplementary Table 8. As shown in Supplementary Fig. 35, the calculated FECO follow the order of Cu97Pd3 (211) < Cu95Sb5 (211) < Cu92Sb5Pd3 (211)−2, which is comparable to the experimental results for all three catalysts. At the steady state, the CO* coverages for CO2RR on different models follow the order of Cu92Sb5Pd3 (211)−2 (1.5%) <Cu92Sb5Pd3 (211)−1 (3%) <Cu95Sb5 (211) (7%) <Cu97Pd3 (211) (51%) <Cu (211) (70%) (Supplementary Fig. 36), which is consistent with the above in situ Raman measurements. As such, reasonably, the Cu92Sb5Pd3 catalyst shows the highest CO2RR activity towards exclusive CO production compared with the bimetallic counterparts or pristine Cu. Beyond the above, to investigate the charge redistribution between Sb/Pd additions and the Cu matrix, Bader charge analysis was also conducted. As shown in Supplementary Fig. 37, on Cu92Sb5Pd3, the copper atoms present partial electron-deficient states, while Sb/Pd atoms express an electron-rich feature, further attesting to the former operando XAS analysis.Fig. 4: DFT calculations.a The calculated adsorption energy and structures of CO* on Cu92Sb5Pd3 (211), Cu92Sb5Pd3 (211)−1 and Cu92Sb5Pd3 (211)−2, where the dashed lines refer to the adsorption energy of CO* on Cu (211) (−0.20 eV), Cu97Pd3 (211) (−0.18 eV) and Cu95Sb5 (211) (−0.11 eV). CO2RR to CO on Cu92Sb5Pd3 (211)−1 (b) and Cu92Sb5Pd3 (211)−2 (c). The initial (IS), transition (TS), and final (FS) structures are shown as insets, where Cu, Sb, Pd, C, O, and H are represented in orange, purple, green, gray, red, and white, respectively. The symbols with the same color represent the same atoms in figures a–c. d Theoretical rates of CO production on Cu92Sb5Pd3 (211)−1 and Cu92Sb5Pd3 (211)−2, where the dashed lines refer to lg(TOF) on Cu (211) (4.89), Cu97Pd3 (211) (5.09) and Cu95Sb5 (211) (5.54).Overall, we showcase an enlightening design principle for creating trimetallic SAAs by alloying Cu with two distinct single-atom metals for the selective CO2RR to CO. Both experimental and theoretical results validate the effectiveness of our design strategy. The synergistic effects of both Sb and Pd single atoms on Cu not only modulate the electronic structure of Cu to favor CO formation and inhibit the HER but also enhance the stability of the catalyst. As a result, the Cu92Sb5Pd3 catalyst exhibits outstanding performance in CO2-to-CO conversion, achieving extremely high current density, near-unity selectivity and robust durability, outperforming many noble metal catalysts. In a broader context, our concept demonstrated here may be further extended to other element combinations and various electrocatalytic reactions.
