Formate Faradaic Efficiency Research Articles

NH4Cl-Assisted Electrosynthesis of P-Doped Co(OH)2 Nanosheet on Cu2S Hollow Nanotube Arrays for Glycerol Electrooxidation.

The glycerol oxidation reaction (GOR) for producing high-value-added organic compounds is of great research interest due to its potential in alleviating the energy crisis. Herein, a facile NH4Cl-assisted electrodeposition strategy is reported to fabricate 3D nano-forest array-like hollow nanostructures. The hierarchical heterojunction by combining phosphorus doping Co(OH)2 nanosheets with Cu2S nanotube arrays (P-Co(OH)2@Cu2S NTs/CF) is developed to realize the optimization on GOR. The optimized P-Co(OH)2@Cu2S NTs/CF catalyst exhibits an exceptional activity with a formate Faradaic efficiency (FE) of 97.40% at a potential of 1.30V (vs RHE). The experimental results indicate that this unique hollow nano-forest structure, grown on a conductive support, can expose more active sites and facilitate electron transfer, thereby demonstrating excellent GOR performance. This work provides new opportunities for the design of electrocatalysts of high-activity and low-cost hollow heterostructure electrocatalysts for glycerol electrooxidation.

Surface Area-Enhanced Cerium and Sulfur-Modified Hierarchical Bismuth Oxide Nanosheets for Electrochemical Carbon Dioxide Reduction to Formate.

Electrochemical carbon dioxide reduction reaction (ECO2RR) is a promising approach to synthesize fuels and value-added chemical feedstocks while reducing atmospheric CO2 levels. Here, high surface area cerium and sulfur-doped hierarchical bismuth oxide nanosheets (Ce@S-Bi2O3) are develpoed by a solvothermal method. The resulting Ce@S-Bi2O3 electrocatalyst shows a maximum formate Faradaic efficiency (FE) of 92.5% and a current density of 42.09mA cm-2 at -1.16V versus RHE using a traditional H-cell system. Furthermore, using a three-chamber gas diffusion electrode (GDE) reactor, a maximum formate FE of 85% is achieved in a wide range of applied potentials (-0.86 to -1.36V vs RHE) using Ce@S-Bi2O3. The density functional theory (DFT) results show that doping of Ce and S in Bi2O3 enhances formate production by weakening the OH* and H* species. Moreover, DFT calculations reveal that *OCHO is a dominant pathway on Ce@S-Bi2O3 that leads to efficient formate production. This study opens up new avenues for designing metal and element-doped electrocatalysts to improve the catalytic activity and selectivity for ECO2RR.

Molecular Engineering of Poly(Ionic Liquid) for Direct and Continuous Production of Pure Formic Acid from Flue Gas.

Electrochemical CO2 reduction reaction (CO2RR) offers a promising approach to close the carbon cycle and reduce reliance on fossil fuels. However, traditional decoupled CO2RR processes involve energy-intensive CO2 capture, conversion, and product separation, which increases operational costs. Here, we report the development of a bismuth-poly(ionic liquid) (Bi-PIL) hybrid catalyst that exhibits exceptional electrocatalytic performance for CO2 conversion to formate. The Bi-PIL catalyst achieves over 90% Faradaic efficiency for formate over a wide potential range, even at low 15% v/v CO2 concentrations typical of industrial flue gas. The biphenyl in PIL backbone affords hydrophobicity while maintaining high ionic conductivity, effectively mitigating the flooding issues. The PIL layer plays a crucial role as a CO2 concentrator and co-catalyst that accelerates the CO2RR kinetics. Furthermore, we demonstrate the potential of Bi-PIL catalysts in a solid-state electrolyte (SSE) electrolyzer for the continuous and direct production of pure formic acid solutions from flue gas. Techno-economic analysis suggests that this integrated process can produce formic acid at a significantly reduced cost compared to the traditional decoupled approaches. This work presents a promising strategy to overcome the challenges associated with low-concentration CO2 utilization and streamline the production of valuable liquid fuels and chemicals from CO2.

In situ activation of Sn(OH)4 catalyst for efficient CO2 electroreduction to formate

Electroreduction of CO2 into the highly valuable fuel formic acid (HCOOH) has been considered an ideal method for converting renewable energy and addressing environmental challenges. Herein, we present a straightforward and rapid method for preparing Sn(OH)4 catalysts specifically designed for electroreducing CO2 to formate. The Sn(OH)4 catalyst obtained through in-situ electrochemical reduction transforms from bulk morphology to nanoporous form, featuring numerous grain boundaries and a high hydroxyl content, enhancing its stability and availability of active sites.The resulting electrocatalyst demonstrates a remarkable formate faradaic efficiency (FEformate) exceeding 80 % across a broad potential range (−0.9 to −1.9 V). Notably, a peak FE value of 92 % is achieved for HCOOH production at −1.7 V vs RHE. This study presents a novel and effective method for developing high-performance Sn-based catalysts.

Plasma-Constructed Co2P-Ni2P Heterointerface for Electro‑Upcycling of Polyethylene Terephthalate Plastic to Co-Produce Hydrogen and Formate.

Integrating electrochemical upcycling of polyethylene-terephthalate (PET) and the hydrogen evolution reaction (HER) is an energy-saving approach for electrolytic hydrogen (H2) production, along with the coproduction of formate. Herein, a novel and rapid strategy of cold plasma phosphating is employed to synthesize Co2P-Ni2P heterointerface decorated on carbon cloth (Co2P-Ni2P/CC) to catalyze H2 generation and reform PET. Notably, the obtained Co2P-Ni2P/CC exhibits eminent ethylene glycol oxidation reaction (EGOR) and HER activities, effectuating low potentials of merely 1.300 and -0.112V versus RHE at 100mAcm-2 for the EGOR and HER, respectively, also attaining an ultralow cell bias of 1.300V at 10mAcm-2 for EG oxidation assisted-water splitting. DFT and characterization results validate that the as-formed built-in electric fields in the Co2P-Ni2P heterointerface can accelerate electrons transfer and deepen structural self-reconstruction, thereby boosting effectively water dissociation and ethylene glycol (EG) dehydrogenation. Impressively, coupling HER with PET-derived EG-to-formate in a flow-cell electrolyzer assembled with Co2P-Ni2P/CC pair achieves an intriguing formate Faradaic efficiency of 90.6% and an extraordinary stable operation of over 70h at 100mAcm-2. The work exemplifies a facile and effective strategy for synthesizing metal phosphides electrocatalysts with extraordinary performance toward H2 generation of water splitting and recycling of PET.

In2O3/Bi2O3 interface induces ultra-stable carbon dioxide electroreduction on heterogeneous InBiOx catalyst

The electrochemical reduction of CO2 (ERCO2) has emerged as one of the most promising methods for achieving both renewable energy storage and CO2 recovery. However, achieving both high selectivity and stability of catalysts remains a significant challenge. To address this challenge, this study investigated the selective synthesis of formate via ERCO2 at the interface of In2O3 and Bi2O3 in the InBiO6 composite material. Moreover, InBiO6 was synthesized using indium-based metal–organic frameworks as precursor, which underwent continuous processing through ion exchange and thermal reduction. The results revealed that the formate Faradaic efficiency (FEformate) of InBiO6 reached nearly 100 % at −0.86 V vs. reversible hydrogen electrode (RHE) and remained above 90 % after continuous 317-h electrolysis, which exceeded those of previously reported indium-based catalysts. Additionally, the InBiO6 composite material exhibited an FEformate exceeding 80 % across a wide potential range of 500 mV from −0.76 to −1.26 V vs. RHE. Density-functional theory analysis confirmed that the heterogeneous interface of InBiO6 played a role in achieving optimal free energies for *OCHO on its surface. Furthermore, the addition of Bi to the InBiO6 matrix facilitated electron transfer and altered the electronic structure of In2O3, thereby enhancing the adsorption, decomposition, and formate production of *OCHO.

(Invited) Elucidating the Cation Effect in CO2 Electroreduction Using Non-Metal Cations

Electrochemical reduction of CO2 may enable a promising route for the recycling of CO2 and the sustainable production of chemicals and fuels. Due to the complex electrochemical environment, a deeper understanding of the reaction mechanism, particularly the role of cations in the process, is still needed. It was recently demonstrated that metal cations are essential for the CO2 reduction to CO, by stabilizing the CO2 – intermediate via electrostatic interaction. Here we investigate the cation effect in CO2 reduction using non-metal cations, particularly quaternary ammonium cations, whose size and shape symmetry can be tuned. We select CO2 reduction on Bi catalyst that produces both CO and formate, thus to reveal and compare the effect of cations on the two reaction pathways. Interestingly, the Faradaic efficiency for CO production increased apparently for the electrolyte with larger cations, while the formate Faradaic efficiency showed a weak dependence on the cation size, indicating a reaction-pathway-dependent effect of the cations. We further compared cations with different symmetries and observed a more profound effect of substituted ammonium cations on the CO2 reduction activity and selectivity, which was attributed to the charge distribution and weak hydration shells of the cations that help stabilize reaction intermediates. Our work elucidates the critical role of cations in the CO2 electroreduction catalysis and suggests a method to improve the electrocatalysis with optimized electrolytes.

Exploring Oxygen Vacancy Effect in 1D Structural SnIP for CO2 Electro-Reduction to Formate.

1D nanostructures exhibit a large surface area and a short network distance, facilitating electron and ion transport. In this study, a 1D van der Waals material, tin iodide phosphide (SnIP), is synthesized and used as an electrocatalyst for the conversion of CO2 to formate. The electrochemical treatment of SnIP reconstructs it into a web-like structure, dissolves the I and P components, and increases the number of oxygen vacancies. The resulting oxygen vacancies promote the activity of the CO2 reduction reaction (CO2RR), increasing the local pH of the electrode surface and maintaining the oxidative metal site of the catalyst despite the electrochemically reducing environment. This strategy, which stabilizes the oxidation state of the catalyst, also helps to improve the durability of CO2RR. In practice, 1D structured SnIP catalyst exhibits outstanding performance with >92% formate faradaic efficiency (FEformate) at 300mAcm-2, a maximum partial current density for formate of 343mAcm-2, and excellent long-term stability (>100h at 100mAcm-2 with >86% FEformate). This study introduced a method to easily generate oxygen vacancies on the catalyst surface by utilizing 1D materials and a strategy to improve the durability of CO2RR by stabilizing the oxidation state of the catalyst.

Liquid Metal Alloys Enable Efficient Formate Electrosynthesis

AbstractLiquid metals are an interesting class of materials with the unique combination of metallic nature and liquid fluidity, and have recently been explored in many emerging fields. Their potential applications in catalysis, unfortunately, remain largely untapped. Herein, Ga‐mediated liquid metal alloying as an effective strategy is demonstrated to prepare functional alloys for catalysis. The alloying is carried out by dissolving indium or tin pellets in liquid gallium at room temperature or assisted by gentle heating, giving rise to binary Ga1−xInx and Ga1−xSnx liquid metal alloys with tunable chemical compositions. When further subjected to ultrasonication in water, they are ruptured into nanosized particles with liquid metal cores and thin surface oxide shells. Electrochemical measurements reveal that the liquid metal alloying significantly promotes electrocatalytic CO2 reduction to formate. Taking Ga0.75In0.25 as an example, its formate Faradaic efficiency is enhanced by 10%–20% compared to those of Ga and In, and its formate partial current density is 4–6 times larger than those of Ga and In. This enhancement is rationalized via computational simulations showing that the surrounding of In active sites with Ga atoms deactivates the undesirable reaction pathways to CO or H2, and facilitates selective formate electrosynthesis.

Electrifying HCOOH synthesis from CO2 building blocks over Cu–Bi nanorod arrays

Precise electrochemical synthesis of commodity chemicals and fuels from CO2 building blocks provides a promising route to close the anthropogenic carbon cycle, in which renewable but intermittent electricity could be stored within the greenhouse gas molecules. Here, we report state-of-the-art CO2-to-HCOOH valorization performance over a multiscale optimized Cu-Bi cathodic architecture, delivering a formate Faradaic efficiency exceeding 95% within an aqueous electrolyzer, a C-basis HCOOH purity above 99.8% within a solid-state electrolyzer operated at 100 mA cm-2 for 200 h and an energy efficiency of 39.2%, as well as a tunable aqueous HCOOH concentration ranging from 2.7 to 92.1 wt%. Via a combined two-dimensional reaction phase diagram and finite element analysis, we highlight the role of local geometries of Cu and Bi in branching the adsorption strength for key intermediates like *COOH and *OCHO for CO2 reduction, while the crystal orbital Hamiltonian population analysis rationalizes the vital contribution from moderate binding strength of η2(O,O)-OCHO on Cu-doped Bi surface in promoting HCOOH electrosynthesis. The findings of this study not only shed light on the tuning knobs for precise CO2 valorization, but also provide a different research paradigm for advancing the activity and selectivity optimization in a broad range of electrosynthetic systems.

Leveraging Inherent Structure of Tin Oxide for Efficient Carbonaceous Products Electrosynthesis

AbstractElectrochemical CO2 reduction reaction (CO2RR) holds a great potential for converting CO2 into valuable carbon‐based chemicals and fuels. A promising strategy for enhancing CO2RR performance is the deliberate structural design of electrocatalysts, which can maximize the utilization of inherent structural advantages. In this work, SnO2 nanocubes (NCs) and nanorods (NRs) are synthesized using a surface energy‐driven growth orientation method, where the stable (110) facet and the highly energetic (001) facet constitute the SnO2 nanostructures. Leveraging the inherent structural merits of different facets on SnO2, theoretical calculations reveal that the (001) facet plays a primary role in inhibiting hydrogen evolution reaction (HER), while both (110) and (001) facets are highly favorable for CO2‐to‐formate conversion under the external bias. As a result, SnO2 NCs with a higher facet ratio of (001)/(110) achieve nearly 100% selectivity for the formation of carbonaceous products during CO2RR. More importantly, a maximum partial current density of about 1 A cm−2 with a formate Faradaic efficiency (FE) of over 90% is achieved in a flow cell, distinguishing it from most of the reported Sn‐based electrocatalysts. These results highlight the strategic advantages of leveraging the inherent structure of nanomaterials for efficient CO2RR.

Ni/P clusters perform as a reaction switch dispersed on co-based electrocatalyst for glycerol oxidation coupling with alkaline hydrogen production

In this work, Ni/P clusters have been successfully decorated onto the surface of Co nanoparticles. The surface decoration with Ni/P clusters greatly enhance the electron interaction in the catalytic system. The optimized catalyst exhibits a high activity for electrocatalytic glycerol oxidation coupling with alkaline hydrogen evolution reaction. A hydrogen-producing electrolysis cell with formate faradaic efficiency of 64.5 % has been assembled, which can achieve a decomposition voltage as low as 1.37 V at a current density of 10 mA cm−2. More importantly Ni/P clusters not only serve as real active sites, but also as reaction switches to regulate the progress of oxygen evolution reaction and glycerol oxidation reactions via tunning the reaction pathway. This study provides a scientific insight into developing future reaction switch for electrocatalysis.

Designing Bi‐In2O3 Nanoflower Catalysts for Enhanced Performance of Electrochemical CO2 Reduction to Formate

AbstractElectrochemical CO2 reduction (ECO2RR) is capable of converting CO2 into a wide range of value‐added products under relatively mild conditions. Electrocatalyst with high selectivity and activity is crucial for high efficient ECO2RR. Herein, Bi‐In2O3 nanoflower catalysts with different metal ratios synthesized by wet chemical method are used for ECO2RR to produce formate. The results indicate that the hydrogen evolution activity of the Bi‐In2O3 catalysts during ECO2RR is suppressed at a low level and the activity and selectivity of formate production is related to the ratio of Bi to In content in the catalysts. The optimized Bi‐In2O3 catalyst with the ratio of Bi6In94 can achieve a high formate Faradaic efficiency (FEformate) over 80 % under a wide potential range from −0.7 V to −1.2 V vs. RHE, with the maximum value of 88.1 % at −0.7 V vs. RHE. Meanwhile, the highest formate partial current density reaches 47.7 mA cm−2 at −1.2 V vs. RHE and the current density and Faradaic efficiency remain stable during the 10 h stability test. The enhanced formate formation on Bi‐In2O3 NF can be attributed to the synergistic effect between Bi and In according to the characterizations of the Bi‐In2O3 NF.

Transformation of Bi4Cl2S5 into sub-10 nm Bi2O2CO3 nanowires for electrochemical reduction of CO2

The development of highly efficient catalysts for the selective electrochemical reduction reaction of CO2 (eCO2RR) to high-valued formate remains a challenge in achieving carbon neutrality and renewable energy conversion. In this study, ultrathin Bi4Cl2S5 nanowires, synthesized using different branched-chain thiols as sulfur sources, were reported for the first time as precatalysts for eCO2RR to formate. Systematic material characterization demonstrated that Bi4Cl2S5 can undergo in-situ evolution into Bi2O2CO3 nanowires, serving as the genuine electrocatalyst for eCO2RR. Through the fine-tuning of ligands during the synthesis of Bi4Cl2S5 nanowires, the optimized Bi4Cl2S5-derived Bi2O2CO3 nanowires exhibited a maximum formate Faradaic efficiency (FEformate) of 95.3 % in eCO2RR using a traditional H-cell, surpassing other prepared samples. Furthermore, an FEformate of over 92.9 % was achieved in a wide potential window of 500 mV, and high performance was maintained over 20 h. This outstanding performance is attributed to the high intrinsic activity, accelerated charge transfer, and the large electrochemical active surface area associated with the characteristic sub-10 nm diameter nanowire structure. Moreover, density function theory calculations further revealed that Bi2O2CO3 can reduce the energy barriers for the formation of *OCHO intermediate and bolster formate production. Our work provides a novel synthesis strategy for excellent Bi-based catalysts in electrocatalysis.

Enhanced Electrochemical CO2 Reduction to Formate over Phosphate‐Modified In: Water Activation and Active Site Tuning

AbstractElectrochemical CO2 reduction reaction (CO2RR) offers a sustainable strategy for producing fuels and chemicals. However, it suffers from sluggish CO2 activation and slow water dissociation. In this work, we construct a (P−O)δ− modified In catalyst that exhibits high activity and selectivity in electrochemical CO2 reduction to formate. A combination of in situ characterizations and kinetic analyses indicate that (P−O)δ− has a strong interaction with K+(H2O)n, which effectively accelerates water dissociation to provide protons. In situ attenuated total reflectance surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS) measurements together with density functional theory (DFT) calculations disclose that (P−O)δ− modification leads to a higher valence state of In active site, thus promoting CO2 activation and HCOO* formation, while inhibiting competitive hydrogen evolution reaction (HER). As a result, the (P−O)δ− modified oxide‐derived In catalyst exhibits excellent formate selectivity across a broad potential window with a formate Faradaic efficiency as high as 92.1 % at a partial current density of ~200 mA cm−2 and a cathodic potential of −1.2 V vs. RHE in an alkaline electrolyte.

Enhanced Electrochemical CO2 Reduction to Formate over Phosphate-Modified In: Water Activation and Active Site Tuning.

Electrochemical CO2 reduction reaction (CO2RR) offers a sustainable strategy for producing fuels and chemicals. However, it suffers from sluggish CO2 activation and slow water dissociation. In this work, we construct a (P-O)δ- modified In catalyst that exhibits high activity and selectivity in electrochemical CO2 reduction to formate. A combination of in situ characterizations and kinetic analyses indicate that (P-O)δ- has a strong interaction with K+(H2O)n, which effectively accelerates water dissociation to provide protons. In situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) measurements together with density functional theory (DFT) calculations disclose that (P-O)δ- modification leads to a higher valence state of In active site, thus promoting CO2 activation and HCOO* formation, while inhibiting competitive hydrogen evolution reaction (HER). As a result, the (P-O)δ- modified oxide-derived In catalyst exhibits excellent formate selectivity across a broad potential window with a formate Faradaic efficiency as high as 92.1 % at a partial current density of ~200 mA cm-2 and a cathodic potential of -1.2 V vs. RHE in an alkaline electrolyte.

In Situ Reconstruction of Scalable Amorphous Indium-Based Metal-Organic Framework for CO2 Electroreduction to Formate over an Ultrawide Potential Window.

Amorphous metal-organic frameworks (aMOFs) are highly attractive for electrocatalytic applications due to their exceptional conductivity and abundant defect sites, but harsh preparation conditions of "top-down" strategy have hindered their widespread use. Herein, the scalable production of aMIL-68(In)-NH2 was successfully achieved through a facile "bottom-up" strategy involving ligand competition with 2-methylimidazole. Multiple in situ and ex situ characterizations reveal that aMIL-68(In)-NH2 evolutes into In/In2O3-x as the genuine active sites during the CO2 electrocatalytic reduction (CO2RR) process. Moreover, the retained amino groups could enhance the CO2 adsorption. As expected, the reconstructed catalyst demonstrates high formate Faradaic efficiency values (>90%) over a wide potential range of 800 mV in a flow cell, surpassing most top-ranking electrocatalysts. Density functional theory calculations reveal that the abundant oxygen vacancies in aMIL-68(In)-NH2 induce more local charges around electroactive sites, thereby promoting the formation of HCOO* intermediates. Furthermore, 16 g of samples can be readily prepared in one batch and exhibit almost identical CO2RR performances. This work offers a feasible batch-scale strategy to design amorphous MOFs for the highly efficient electrolytic CO2RR.

Promoting Electrochemical CO2 Reduction to Formate via Sulfur‐Assisted Electrolysis

AbstractElectrochemical CO2 reduction reaction (CO2RR) provides a renewable approach to transform CO2 to produce chemicals and fuels. Unfortunately, it faces the challenges of sluggish CO2 activation and slow water dissociation. This study reports the modification of Bi‐based electrocatalyst by S, which leads to a remarkable enhancement in activity and selectivity during electrochemical CO2 reduction to formate. Based on comprehensive in situ examinations and kinetic evaluations, it is observed that the presence of S species over Bi catalyst can significantly enhance its interaction with K+(H2O)n, facilitating fast dissociation of water molecules to generate protons. Further in situ attenuated total reflectance surface‐enhanced infrared absorption spectroscopy (ATR‐SEIRAS) and in situ Raman spectroscopy measurements reveal that S modification is able to decrease the oxidation state of Bi active site, which can effectively enhance CO2 activation and facilitate HCOO* intermediate formation while suppressing competing hydrogen evolution reaction. Consequently, the S‐modified Bi catalyst achieves impressive electrochemical CO2RR performance, reaching a formate Faradaic efficiency (FEformate) of 91.2% at a formate partial current density of ≈135 mA cm−2 and a potential of −0.8 V versus RHE in an alkaline electrolyte.

Synergistic Effects of Doping and Strain in Bismuth Catalysts for CO2 Electroreduction.

Doping is a recognized method for enhancing catalytic performance. The introduction of strains is a common consequence of doping, although it is often overlooked. Differentiating the impact of doping and strain on catalytic performance poses a significant challenge. In this study, Cu-doped Bi catalysts with substantial tensile strain are synthesized. The synergistic effects of doping and strain in bismuth result in a remarkable CO2RR performance. Under optimized conditions, Cu1/6-Bi demonstrates exceptional formate Faradaic efficiency (>95%) and maintains over 90% across a wide potential window of 900 mV. Furthermore, it delivers an industrial-relevant partial current density of -317 mA cm-2 at -1.2 VRHE in a flow cell, while maintaining its selectivity. Additionally, it exhibits exceptional long-term stability, surpassing 120 h at -200 mA cm-2. Through experimental and theoretical mechanistic investigations, it has been determined that the introduction of tensile strain facilitates the adsorption of *CO2, thereby enhancing the reaction kinetics. Moreover, the presence of Cu dopants and tensile strain further diminishes the energy barrier for the formation of *OCHO intermediate. This study not only offers valuable insights for the development of effective catalysts for CO2RR through doping, but also establishes correlations between doping, lattice strains, and catalytic properties of bismuth catalysts.

Proton-rich two-dimensional defective Bi2S3-derived nanosheets for boosting CO2 electroreduction

Bismuth (Bi)-based catalysts have attracted great attention in electrocatalytic CO2 reduction into formate, but suffer from modest activity due to insufficient active sites and slow protonation process. Here, two-dimensional (2D) defect-rich Bi2S3 nanosheets are first achieved through chemical vapor sulfurization of Bi2O3 solids. It is found that the defects enable the stable immobilization of S heteroatoms into 2D Bi lattice. A combination of computational and experimental analyses reveal that S dopants can not only facilitate water dissociation to construct proton-rich surface, but also concentrate potassium cations to stabilize *OCHO intermediates. Further cooperating with defects, the *OCHO formation can be both kinetically and thermodynamically boosted. Remarkably, the constructed Bi2S3 nanosheets exhibit a high formate Faradaic efficiency (>90%) over a wide potential window and a high intrinsic stability over 200 h. The excellent performance in flow cell as well as promising solar-driven CO2 electrocatalysis further demonstrate the great potential for practical implementation.