CO2 Electroreduction Activity Research Articles

Adsorbate-induced adatom formation on Au-Cu bimetallic alloys and its possible consequences for CO2 electroreduction

The adsorbate-induced formation of sub-nanometer clusters on transition-metal single crystals observed in previous high-pressure microscopic studies hinted at the in-situ formation of unique active sites even on large nanoparticle catalysts. We propose that the adatom formation energy can be used as an energetic descriptor for the initial step toward the adsorbate-induced metal-cluster formation process. This descriptor can be efficiently computed using density functional theory (DFT) calculations and applied for screening and identification of metal catalysts where this phenomenon may play an important role in generating active sites in-situ. As a proof of concept, here, we construct an adatom formation energy database for three AuxCuy alloys (x:y = 3:1, 1:1, or 1:3) and eighteen adsorbates (H, C, N, O, F, S, Cl, Br, I, CHx, NHx (x = 1 – 3), CO, NO, and OH) commonly involved in catalytic reactions. The energetics of adatom formation were examined in all cases where the (111) terrace, (211) step-edge, and (874) kink were the sources of the adatom. We demonstrate that the presence of an adsorbate could alter not only the energetics for adatom formation but also the elemental nature of the preferred adatom being formed. Using our database, we identified promising systems which favor adsorbate-induced adatom formation under near-ambient conditions. Specifically, CO-induced adatom formation on all three Au-Cu alloy surfaces could occur under CO2 electroreduction (CO2RR) conditions. This phenomenon offers a qualitative explanation for the experimentally observed CO2RR activity on Au-Cu alloy catalysts. Our methodology offers an easily expandable and efficient approach for large-scale catalyst screening with regards to adatom/cluster formation under reaction conditions and provides insight into the possible nature of active sites on alloy catalysts from a novel perspective.

Revealing the Origin of Graphene Anchored Single Palladium Atom for Electrochemical CO2 Reduction to Syngas with Tunable CO/H2 Ratios

AbstractPd based catalysts are rare metal‐based catalyst to yield tunable CO/H2 ratios for Fischer‐Tropsch synthesis. How to achieve the co‐production of CO and H2 with as little Pd as possible is extremely meaningful for Cn industry. Recent experiment revealed single Pd atom anchored on graphene exhibits high activity for CO2 electroreduction to syngas, yet the origin of activity and controllable CO/H2 ratios, especially the exact Pd coordination structure, remains elusive. Here we employ grand‐canonical density functional theory to show that Pd−N1, rather than the commonly accepted Pd‐N4, serves as the active center, and the charge‐carrying capability is an effective descriptor. The site with more Pd−C coordination can better submerge in graphene‘s delocalized π electrons for higher charge‐carrying capacity to carry excess charges that occupy Pd 4dz2 orbital and promote electron injection. Importantly, the tunable CO/H2 ratio can be explained with difference in charge‐carrying capability of transition state for *COOH and *H2 formation. This work solves the puzzle of coordinating structure of Pd active site and demonstrates the important role of charge‐carrying capability in electrochemical process, which shall provide a reference for further exploration of efficient electrocatalysts.

Competition between Initial CO2 Electroreduction and Hydrogen Evolution Reaction on Cu Catalysts in Acidic Media: Role of Specifically Adsorbed Halide Anions.

The role of halide anions and competing mechanisms between initial CO2 electroreduction pathways and hydrogen evolution reaction (HER) are systematically identified at halide anions modified Cu(111)/H2O interfaces based on density functional theory calculations in this paper. The present results show that halide anions modified Cu(111)/H2O interfaces can notably enhance electroreduction activity of CO2 into CO. Simultaneously, it is concluded that the specifically adsorbed halide anions modified Cu electrodes can inhibit HER by studying competing HER mechanisms, and thus the enhanced CO2 electroreduction activity can be ascribed to the suppressed HER. The origin of enhanced CO production activity and inhibited HER is further scrutinized. The present results show that the presence of halide anions can lead to stronger CO adsorption and the increased adsorption strength of CO can explain easier CO production based on the Sabatier principle. Interestingly, the calculated results show that the presence of halide anions does not exert an effect on H adsorption strength, which is regarded as a key descriptor of HER activity, implying that halide anions modified Cu electrodes may be not able to directly lead to the inhibited HER. However, the present results indicate that co-adsorbed CO can weaken adsorption strength between H and Cu electrodes and thus result in inhibited HER and decreased HER activity. The upshift of d-band centers of surface Cu atoms due to modification of halide anions may be a reason for stronger CO adsorption, whereas the downshift of the d-band center due to the presence of co-adsorbed CO can lead to a weakening effect on H adsorption strength. Our present insights into the role of halide anions can aid in designing an optimal electrolyte and developing electrocatalysts that are more selective toward CO2 electroreduction than HER.

Defect anchored single atomic Tin-nitrogen sites on graphene nanomesh for enhanced CO2 electroreduction to CO

Developing Sn, nitrogen-doped carbon catalysts (Sn-NC) for efficient CO2 electroreduction (CO2RR) to CO remains a great challenge. Here, we employed a defective hierarchical porous graphene nanomesh to anchor the single atomic tin-nitrogen sites (A-Sn-NGM) for effective CO2 electroreduction. The synthesized A-Sn-NGM typically showed remarkable CO2RR activity towards CO production, which achieved a maximum CO Faradaic efficiency (FECO) of 98.7 % and a turnover frequency of 5117.4 h−1 at a potential of −0.6 V (vs. RHE). Further analysis proves that the increased activity to CO production of A-Sn-NGM derives from the enlarged roughness and enhanced intrinsic activity. Density-functional theory (DFT) calculations indicate that the adjacent carbon defects anchored Sn-Nx coordination sites can markedly inhibit the competing hydrogen evolution reaction (HER) and lower the energy barrier for the formation of *COOH intermediates as compared to bulk Sn-Nx sites without carbon defects. This work provides a reliable method by engineering the carbon support to improve the CO2RR performance for single-atom catalysts.

Nitrided copper-iron composite oxides derived from layered double hydroxides for enhanced carbon dioxide electroreduction to methane and formic acid

The reduction of carbon dioxide into valuable chemical products is a promising solution to address carbon balance and energy issues. Herein, amorphous nitrided copper-iron oxides are prepared by gas-phase nitriding of CuFe-layered double hydroxide precursors with urea as a nitrogen source. The obtained materials show high activity for CO2 electroreduction to methane and formic acid, achieving a total Faraday efficiency of 74.7% at −0.7 V vs. RHE and exhibiting continuous 10 h durability in the H-cell. The uniformly distributed Cu+ sites act as active sites by losing electrons to activate CO2. During the CO2 electroreduction, CO2 is converted to *COOH via proton-electron coupling; *COOH combines directly with a proton in solution to produce the HCOOH product; and the other part of *COOH undergoes a protonated dehydration process to form the *CHO intermediate, which dehydrates again to form CH4. This study provides a new approach for designing CO2 electroreduction catalysts.

Activating Inert Perovskite Oxides for CO2 Electroreduction via Slight Cu2+ Doping in B-Sites.

Perovskite oxides are proven as a striking platform for developing high-performance electrocatalysts. Nonetheless, a significant portion of them show CO2 electroreduction (CO2RR) inertness. Here a simple but effective strategy is reported to activate inert perovskite oxides (e.g., SrTiO3) for CO2RR through slight Cu2+ doping in B-sites. For the proof-of-concept catalysts of SrTi1-xCuxO3 (x=0.025, 0.05, and 0.1), Cu2+ doping (even in trace amount, e.g., x=0.025) can not only create active, stable CuO6 octahedra, increase electrochemical active surface area, and accelerate charge transfer, but also significantly regulate the electronic structure (e.g., up-shifted band center) to promote activation/adsorption of reaction intermediates. Benefiting from these merits, the stable SrTi1-xCuxO3 catalysts feature great improvements (at least an order of magnitude) in CO2RR activity and selectivity for high-order products (i.e., CH4 and C2+), compared to the SrTiO3 parent. This work provides a new avenue for the conversion of inert perovskite oxides into high-performance electrocatalysts toward CO2RR.

Extrinsic hydrophobicity-controlled silver nanoparticles as efficient and stable catalysts for CO2 electrolysis.

To realize economically feasible electrochemical CO2 conversion, achieving a high partial current density for value-added products is particularly vital. However, acceleration of the hydrogen evolution reaction due to cathode flooding in a high-current-density region makes this challenging. Herein, we find that partially ligand-derived Ag nanoparticles (Ag-NPs) could prevent electrolyte flooding while maintaining catalytic activity for CO2 electroreduction. This results in a high Faradaic efficiency for CO (>90%) and high partial current density (298.39 mA cm‒2), even under harsh stability test conditions (3.4 V). The suppressed splitting/detachment of Ag particles, due to the lipid ligand, enhance the uniform hydrophobicity retention of the Ag-NP electrode at high cathodic overpotentials and prevent flooding and current fluctuations. The mass transfer of gaseous CO2 is maintained in the catalytic region of several hundred nanometers, with the smooth formation of a triple phase boundary, which facilitate the occurrence of CO2RR instead of HER. We analyze catalyst degradation and cathode flooding during CO2 electrolysis through identical-location transmission electron microscopy and operando synchrotron-based X-ray computed tomography. This study develops an efficient strategy for designing active and durable electrocatalysts for CO2 electrolysis.

Achieving high selectivity and activity of CO2 electroreduction to formate by in-situ synthesis of single atom Pb doped Cu catalysts

Exploring highly selective and stable electrocatalysts is of great significance for the electrochemical conversion of CO2 into fuel. Herein, a three-dimensional (3D) nanostructure catalyst was developed by doping Pb single-atom (PbSA) in-situ on carbon paper (PbSA100-Cu/CP) through a low-energy and economical method. The designed catalyst exhibited abundant active sites and was beneficial to CO2 adsorption, activation, and subsequent conversion to fuel. Interestingly, PbSA100-Cu/CP showed a prominent Faraday efficiency (FE) of 97 % at –0.9 V versus reversible hydrogen electrode (vs. RHE) and a high partial current density of 27.9 mA·cm−2 for formate. Also, the catalyst remained significantly stable for 60 h during the durability test. The reaction mechanism was investigated by density functional theory (DFT), demonstrating that the doping PbSA induced the electrons redistribution, promoted the formate generation, reduced the rate-determining step (RDS) energy barrier, and inhibited the hydrogen evolution reaction. The study aims to provide a new strategy for developing of single-atom catalysts with high selectivity and stability, which will help reduce environmental pressure and alleviate energy problems.

Guanine-derived F, N co-doped carbon-shell encapsulated iron carbide nanoparticles for enhanced CO2 electroreduction activity

Guanine-derived F, N co-doped carbon-shell encapsulated iron carbide nanoparticles for enhanced CO2 electroreduction activity

Promoting CO2 electroreduction activity of porphyrinic conjugated microporous polyanilines via accelerating proton transfer dynamics

Conjugated microporous polymers (CMPs) with π-conjugated framework, inherent porosity and tunable structure have been considered as the promising platforms as electrocatalysts for carbon dioxide reduction reaction (CO2RR). Promoting the proton...

Effect of peptide aerogel composite on silver nanoparticles as a catalyst for electrochemical CO2 reduction

Electrochemical reduction of carbon dioxide (CO2RR) product distribution has been found to be dependent on several key factors, such as catalyst surface morphology, stability, and porosity. Metal-modified carbon-based materials have received a lot of attention in CO2RR. However, designing a highly active metal carbon catalyst for CO2RR utilizing low-cost chemical precursors remains a challenge. Here, a series of myristic acid-Phe-Phe peptide (MA-FF) aerogel materials containing graphene oxide (Gox) and Ag nanoparticles have been prepared for electrochemical CO2RR. The morphologies of the composites were studied by scanning electron microscopy (SEM), and their surface compositions were determined using X-ray photoelectron spectroscopy (XPS). While the peptide aerogel alone showed no catalytic activity for CO2 electroreduction, the addition of Ag nanoparticles results in a Faradaic efficiency (FE) of 46% for electroreduction of CO2 to CO at an overpotential of − 0.8 V vs. RHE. Incorporation of Gox in the aerogel increases the FE to 88% and allows CO2 reduction at a lower overpotential of − 0.7 V vs. RHE. Using highly porous peptide aerogels-Gox in addition to the metal active center provides an enhanced and new method for CO2 conversion using low environmental impact bio-based aerogels.

Dynamic Metal-Ligand Coordination Boosts CO2 Electroreduction.

The interfacial structure of heterogeneous catalysts determines the reaction rate by adjusting the adsorption behavior of reaction intermediates. Unfortunately, the catalytic performance of conventionally static active sites has always been limited by the adsorbate linear scaling relationship. Herein, we develop a triazole-modified Ag crystal (Ag crystal-triazole) with dynamic and reversible interfacial structures to break such a relationship for boosting the catalytic activity of CO2 electroreduction into CO. On the basis of surface science measurements and theoretical calculations, we demonstrated the dynamic transformation between adsorbed triazole and adsorbed triazolyl on the Ag(111) facet induced by metal-ligand conjugation. During CO2 electroreduction, Ag crystal-triazole with the dynamically reversible transformation of ligands exhibited a faradic efficiency for CO of 98% with a partial current density for CO as high as -802.5 mA cm-2. The dynamic metal-ligand coordination not only reduced the activation barriers of CO2 protonation but also switched the rate-determining step from CO2 protonation to the breakage of C-OH in the adsorbed COOH intermediate. This work provided an atomic-level insight into the interfacial engineering of the heterogeneous catalysts toward highly efficient CO2 electroreduction.

Modifying Copper Local Environment with Electrolyte Additives to Alter CO2 Electroreduction vs Hydrogen Evolution

CO2 electroreduction (CO2ER) by using renewable energy resources is a promising method to mitigate the CO2 level in the atmosphere as well as produce valuable chemicals. Local environment at the electrode–electrolyte interface plays a key role in CO2ER activity and selectivity along with its competing hydrogen evolution reaction (HER). In addition to the catalyst and reactor design, electrolyte also has a significant impact on the interface. Herein, electrolyte additives were used to modify the local environment around the Cu catalyst during CO2ER. For this purpose, 10 mM ionic additives with bis(trifluoromethylsulfonyl)imide ([NTF2]−) and dicyanamide ([DCA]−) as anions and 1-butyl-3-methylimidazolium ([BMIM]+), potassium (K+), or sodium (Na+) as cations have been added to an aqueous potassium bicarbonate solution (0.1 M KHCO3). COMSOL Multiphysics was also used to calculate the local pH and CO2 concentration at the electrode–electrolyte interface in different electrolytes. Results showed that the local environment modifications by the electrolyte additives altered the activity and selectivity of Cu in CO2ER. It was found that the CO2ER activity at −0.92 V was enhanced when using anions with high CO2 affinity and high hydrophobicity, such as [NTF2]−. Among [NTF2]−-based additives, [BMIM][NTF2] had a higher faradaic efficiency (FE) for formate (38.7%) compared to K[NTF2] (23.2%) and Na[NTF2] (18.5%) at −0.92 V likely due to the presence of imidazolium cations that can further stabilize the intermediates on the surface and enhance CO2ER. Electrolytes containing [DCA]−-based additives with high hydrophilicity and low CO2 affinity had a very high HER selectivity (>90% FEH2) and low CO2ER selectivity regardless of the cation nature. This observation is attributed to the presence of hydrophilic [BMIM][DCA] in the vicinity of the catalyst, which impacts the microenvironment around the catalyst. We observed that [DCA]− anions have a high affinity to adsorb on Cu catalysts as soon as the catalyst is submerged in the electrolyte. Although FTIR showed that [DCA]− anions desorb from the surface at negative potentials, it is likely that [DCA]− anions still remain in the proximity of the electrode, next to the adsorbed cations, impacting the transport of H2O and CO2, and altering the product selectivity. COMSOL calculations showed that the local pH is directly proportional to the H2 evolution activity. Also, hydrophilic salts such as those with the [DCA]− anion had a more alkaline local pH, which led to a lower CO2 concentration in the vicinity of the catalyst.

Temperature-Induced Low-Coordinate Ni Single-Atom Catalyst for Boosted CO2 Electroreduction Activity.

Single-atom catalysts (SACs) exhibit remarkable potential for electrochemical reduction of CO2 to value-added products. However, the commonly pursued methods for preparing SACs are hard to scale up, and sometimes, lack general applicability because of expensive raw materials and complex synthetic procedures. In addition, the fine tuning of coordination environment of SACs remains challenging due to their structural vulnerability. Herein, a simple and universal strategy is developed to fabricate Ni SACs with different nitrogen coordination numbers through one-step pyrolysis of melamine, Ni(NO3 )∙6H2 O, and polyvinylpyrrolidone at different temperatures. Experimental measurements and theoretical calculations reveal that the low-coordinate Ni SACs exhibit outstanding CO2 reduction performance and stability, achieving a Faradic efficiency (FECO ) of 98.5% at -0.76V with CO current density of 24.6mA cm-2 , and maintaining FECO of over 91.0% at all applied potential windows from -0.56 to -1.16V, benefiting from its coordinatively unsaturated structure to afford high catalytic activity and low barrier for the formation of *COOH intermediate. No significant performance degradation is observed over 50 h of continuous operation. Additionally, several other metallic single-atom catalysts are successfully prepared by this synthetic method, demonstrating the universality of this strategy.

Indium oxide induced electron-deficient indium hollow nanotubes for stable electroreduction of CO2 at industrial current densities

Despite high selectivity for CO2 electroreduction to formate, the current density and stability over indium-based catalysts are far from the requirements of industrial applications. Herein, we report an aminated In-MOF-derived In/In2O3 hollow nanotube catalyst (In/In2O3 Ho-nt), which can maintain a stable In0/In3+ heterostructure during the CO2 electrocatalysis. The stable In0/In3+ species boosts the formate FE (Faradaic efficiency) to over 90% with a highest current density of ∼ 650 mA cm−2 in a wide potential range from −0.8 V to −1.2 V vs. RHE in flow cells. More impressively, In/In2O3 Ho-nt demonstrates a full-cell EE (energy efficiency) of 44.5% and a long-term stability of 70 h at a current density of 200 mA cm−2 in membrane electrode assembly (MEA) cells by controlling the hydrophobicity of the catalyst interface. DFT calculations reveal that the charge redistribution between In3+ and In0 sites endows In0 sites with an electron-deficient environment, which enhances the adsorption capacity of CO2* intermediate and accelerates charge transfer kinetics, thus improving the activity of CO2 electroreduction to formate.

The axial ligands optimized activity of CO2 electroreduction to CO over penta-coordinated single atom iron–nitrogen–carbon catalysts

Metal-nitrogen-carbon materials, especially Fe–N–C, are currently at the forefront of interests in electrocatalysis owing to their low price and excellent performance in electrochemical CO2 reduction reaction (CO2RR). It was reported recently that Fe4N and Fe2N modified FeN4 structures, namely penta-coordinated FeN4–L with an axial ligand, would show better performance than the pristine FeN4 structure for CO2 reduction reaction. In this work, microkinetic models were developed and the production rate of CO was calculated over FeN4-based structures. The results suggested that the weaker adsorption of CO over FeN4-L structures, which is originated from the weakened donation and backdonation between CO and the central Fe upon ligand coordination, significantly enhances the CO production rate. Inspired by these results, we further constructed 27 penta-coordinated single iron models with axial ligands and addressed the CO production rate explicitly, and several candidates that would show high activity towards the CO production are identified from the activity map.

Achieving Tunable Selectivity and Activity of CO2 Electroreduction to CO via Bimetallic Silver-Copper Electronic Engineering.

Limited comprehension of the reaction mechanism has hindered the development of catalysts for CO2 reduction reactions (CO2 RR). Here, the bimetallic AgCu nanocatalyst platform is employed to understand the effect of the electronic structure of catalysts on the selectivity and activity for CO2 electroreduction to CO. The atomic arrangement and electronic state structure vary with the atomic ratio of Ag and Cu, enabling tunable d-band centers to optimize the binding strength of key intermediates. Density functional theory calculations confirm that the variation of Cu content greatly affects the free energy of *COOH, *CO (intermediate of CO), and *H (intermediates of H2 ), which leads to the change of the rate-determining step. Specifically, Ag96 Cu4 reduces the free energy of the formation of *COOH while maintaining a relatively high theoretical overpotential for hydrogen evolution reaction(HER), thus achieving the best CO selectivity. While Ag70 Cu30 shows relatively low formation energy of both *COOH and *H, the compromised thermodynamic barrier and product selectivity allows Ag70 Cu30 the best CO partial current density. This study realizes the regulation of the selectivity and activity of electrocatalytic CO2 to CO, which provides a promising way to improve the intrinsic performance of CO2 RR on bimetallic AgCu.

Theoretical understanding of the effect of specifically adsorbed halide anions on Cu-catalyzed CO2 electroreduction activity and product selectivity.

Initial CO2 electroreduction into CO and its subsequent electroreduction pathways were selected to study the effect of specifically adsorbed halide anions X- (X = F, Cl, Br, I) on CO2 electroreduction activity and product selectivity at Cu(111)/H2O interfaces via DFT calculations. The calculated results show that the presence of halide anions can exert a notable effect on the CO2 adsorption characteristics and that chemically adsorbed CO2 molecules can be formed. Furthermore, the halide-anion-modified Cu(111)/H2O interfaces could significantly enhance the initial CO2 electroreduction into CO activity, which is regarded as the rate-determining step during CO2 electroreduction at clean Cu(111)/H2O interfaces. Analysis of the initial CO2 electroreduction and Volmer reaction pathways showed that the halide-anion-modified Cu(111)/H2O interfaces could suppress the HER and thus improve the CO2 electroreduction activity and product selectivity. It is speculated that the enhanced initial CO2 electroreduction activity at the F--, Cl--, Br--, and I--modified Cu(111)/H2O interfaces may originate from the decreased work functions and anion radical ·CO2- formations. Simultaneously, we concluded that dimer OCCO formations in the presence of halide anions were more favorable than CHO during CO electroreduction according to the order of I- > Br- > Cl- > F- and could result in the production of C2 product, suggesting an improved CO2 electroreduction product selectivity. The present analyses of electronic structure may explain the more favorable OCCO formations in the order of I- > Br- > Cl- > F-. The present understanding of this effect will provide an improved scientific guideline for the control of CO2 electroreduction pathways and design of more efficient electrocatalysts.

APPLICATION OF SQUARE WAVE POTENTIAL REGIME TO ELECTRO REDUCTION OF CO2 IN ETHANOLAMINE INTO ETHYL CARBAMATE BY PALLADIUM ELECTRODE

Electrochemical reduction of the CO2 present in 0.1 M Ethanolamine (EA) aqueous solution at Palladium metal electrodes for the synthesis of ethyl carbamate (CH3CH2OC(O)NH2) is investigated. The application square wave potential regime of the carbon dioxide in (EA) to be reduced to an organic product. In addition to identifying optimal conditions for CO2 electrocatalysis reduction by the square wave potential regime, the potential value was between - 1.0 to 0.4 V with 1.4 V amplitude, the time of reaction was 4 hours and the frequency was 100 Hz. We have carried out reactions at various pH levels and different voltages in an alkaline environment to ensure optimal conditions for the production of ethyl carbamate. The palladium catalysts electrode has demonstrated high CO2 electro-reduction activity to the organic compound. The organic product was analyzed by cyclic voltammetry, NMR, UV spectrometry, FT-IR spectroscopy, TGA, and MS. The results suggest the reduction of CO2-saturated in 0.1 M ethanolamine to ethyl carbamate, C2H5OCONH2. The Faradaic Efficiency and current density of electro-convert CO2-saturated in ethanolamine to ethyl carbamate are 93% and 71 mA cm−2, respectively

Cu-THQ-EFG Composite for Highly Selective Electrochemical CO2 Reduction to Formate at Low Overpotentials

Metal organic framework (MOFs) are promising materials for electrocatalysis. However, the active sites of bulk MOFs crystal normally cannot be fully utilized because of the slow reagent penetration of pores and blockage of active sites. Herein, we report a facile way to deposit copper-benzoquinoid (Cu-THQ) on the edge-functionalized graphene (EFG) which prevented material's aggregation. EFG used as a substrate provides higher electrical conductivity and stability in water than previously utilized graphene oxide (GO). Besides, the plate-like morphology of EFG proved to be more beneficial to support the MOF, because of the functional groups on its edge regions and much lower resistance compared to the sheet GO. Therefore, EFG can boost the resultant material's catalytic activity for CO2 electroreduction (CO2RR). Furthermore, Cu-THQ exhibits high selectivity for formate formation in CO2RR. Representing as the only CO2 reduced liquid product, formate can be separated from gaseous products and further extracted from the electrolyte for practical use. The electrocatalytic results of Cu-THQ-EFG indicate the composite exhibits a higher current density of -3 mA/cm2 and faradaic efficiency of -0.25 V vs. RHE, corresponding to 50 mV of overpotential. Moreover, it features a less negative on-set potential of -0.22 V vs. RHE, which is close to the equilibrium potential of CO2RR (-0.2 V vs. RHE) and is 0.16 V more positive than the on-set potential of Cu-THQ-GO (-0.38 V vs. RHE).