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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

One-Step Facile Synthesis of High-Activity Nitrogen-Doped PtNiN Oxygen Reduction Catalyst

PtM alloy electrocatalysts (M = Fe, Co, Ni) have been the subject of many investigations aimed at increasing their attractive properties, in particular oxygen reduction reaction (ORR) activity, while reducing total platinum-group-metal content and improving durability. Despite some success, these catalysts still have relatively high Pt content and lack the necessary durability as M metals leach out from the alloys during potential cycling. Previously, we synthesized nitrogen (N)-doped PtMN/C catalysts consisting of thin Pt shells on M nitride cores by a two-step method, which showed higher ORR activity and stability than their PtM counterparts. In the present work, we developed a facile one-step synthesis method, which comprises a single thermal annealing process of the N-doped PtNiN/C alloy. The ORR performance of the one-step synthesized PtNiN/C catalyst is much higher than that of the two-step synthesized PtNiN/C, as revealed by rotating disk electrode measurements. Membrane electrode assembly fuel cell testing demonstrated superb durability and high activity. Formation of Pt monolayer shells on the nitrided (Pt x Ni 1-x ) 4 N cores was confirmed by in situ X-ray absorption spectroscopy. The origins of the enhanced activity and stability of the one-step synthesized PtNiN/C catalyst are elucidated based on density functional theory calculations together with the experimental results.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2023

Spectroscopic Characterization of Highly Active Fe–N–C Oxygen Reduction Catalysts and Discovery of Strong Interaction with Nafion Ionomer

Scaling up clean-energy applications necessitates the development of platinum group metal (PGM)-free fuel cell electrocatalysts with high activity, stability, and low cost. Here, X-ray absorption (XAS) at the Fe K-edge and Fe K β X-ray emission (XES) spectroscopies were used to study the electronic structure of Fe centers in highly active Fe–N–C oxygen reduction catalysts with significant commercial potential. X-ray absorption near-edge structure (XANES) analysis has shown that the majority (>95%) of Fe centers are in the Fe 3+ oxidation state, while extended X-ray absorption fine structure (EXAFS) detected a mixture of single site Fe–N 4 centers (>95%) and centers with short (~2.5 Å) Fe–Fe interactions of Fe metal and/or Fe-carbide nanoparticles (<5%) featuring the Fe o oxidation state. Surprisingly, addition of Nafion, the most widely used ionomer, resulted in pronounced changes in the XAS spectra, consistent with a strong catalyst–ionomer interaction where long Fe–Fe interactions at ~3.1 Å were shown to be a feature of Fe 3+ ions bound with the Nafion. We conclude that exposure to Nafion during the device formulation has a different effect from the aggressive acid leaching typically used in the preparation of Fe–N–C catalysts. Furthermore, it was hypothesized that the polymer interacts with single sites’ Fe 3+ centers, as well as with graphene layers protecting the Fe o nanoparticles, and extracts some Fe ions into the Nafion matrix.

25 ENERGY STORAGE↗
DOE OSTI2026

Evaluating Ru-RuO 2 @BN as a Bifunctional Electrocatalyst for the Nitrogen Reduction Reaction and the Hydrogen Evolution Reaction

Electrochemical approaches toward clean energy production have been the focus of significant attention. Here, the nitrogen (N 2 ) reduction reaction (NRR) and the hydrogen (H 2 ) evolution reaction (HER) offer a promising method for producing NH 3 and H 2 , respectively. Nevertheless, practical obstacles that must be overcome in creating optimal catalysts are the sluggish kinetics and low selectivity of NRR and HER. Herein, we report on the synthesis of a Ru-RuO 2 -decorated boron nitride (BN) catalyst that shows excellent activity toward NRR. A rate of NH3 formation (V NH3 ) of 16.8 μg h -1 mg -1 and a corresponding Faradaic efficiency (FE) of 52.9% were noted at a potential of −0.5 V in 0.1 M HCl. However, the HER activity of Ru-RuO 2 @BN was found to be highly suppressed in 0.1 M HCl and did not yield a reasonable overpotential value. Thus, the capability of this material toward NRR suggests its viability as a promising catalyst for clean NH 3 production.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2019

Improved Oxygen Reduction Reaction Activity of Nanostructured CoS 2 through Electrochemical Tuning

Searching for efficient Pt-free oxygen reduction reaction (ORR) electrocatalysts has been actively pursued among the current electrocatalyst research community. The family of transition-metal chalcogenides, especially cobalt disulfide (CoS 2 ), has been reported as competitive ORR catalysts. In this work, we perform a detailed analysis of the intrinsic activity in terms of onset potentials and selectivity toward hydrogen peroxide of CoS 2 in both acid and alkaline medium. Our detailed characterizations of this system via X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and calculated bulk and surface thermodynamics and ORR mechanism reveal pH-dependent electrochemical evolution of the CoS 2 surfaces. Using XPS results before and after ORR in combination with density functional theory (DFT) calculations for individual surfaces reveals sulfur to oxygen substitution, and partial dissolution occurs in acidic media, while thin cobalt oxide films supported by CoS 2 are formed in alkaline media. The comprehensive DFT calculations of the ORR activities on these systems reveal that sulfur is an unlikely ORR active site, while undercoordinated Co metal site in the CoS 2 is less active than very active undercoordinated Co metal site in the Co oxide film. Using these guiding principles, we then demonstrate that electrochemical lithium (Li) tuning of CoS 2 in organic electrolyte increases its ORR performance in both acid and alkaline medium. Detailed characterizations demonstrate that the grain size of CoS 2 particle is considerably reduced and has a much richer surface oxygen content after electrochemical Li tuning (LiET-CoS 2 ) as the direct consequence of the Li galvanostatic cycling. The general efficacy of this method toward transition-metal chalcogenides (T-M-X) is further demonstrated by enhanced ORR activities of CoS and Ni 3 S 2 in alkaline and neutral medium, respectively. This work opens up an opportunity for probing more advanced T-M-X-based catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Graphite Intercalation Compounds Derived by Green Chemistry as Oxygen Reduction Reaction Catalysts

Precious group metal (PGM) catalysts such as Pt supported on carbon supports are expensive catalysts utilized for the oxygen reduction reaction (ORR) due to their unmatched catalytic activity and durability. As an alternative, PGM-free ORR electrocatalysts that offer respectable catalytic activity are being pursued. Most of the notable PGM-free catalysts are obtained either from a bottom-up approach synthesis utilizing nitrogen-rich polymers as building blocks, or from a top down approach, where nitrogen and metal moieties are incorporated to carbonaceous matrixes. The systematic understanding of the origin of catalytic activity for either case is speculative and currently employed synthesis techniques typically generate large amounts of hazardous waste such as acids, oxidizing agents, and solvents. Herein, for the first time, we investigate the catalytic activity of graphite-based materials obtained via intercalation strategies that minimally perturb the graphitic backbone. Here, our outlined approaches demonstrate initial efforts to not only elucidate the role of each element but also significantly reduce the use of hazardous chemicals, which remains a pressing challenge. Graphite intercalation compounds (GIC) were obtained using fewer steps and solvent-free processes. X-ray diffraction and Raman results confirm the successful intercalation of FeCl 3 between graphite layers. Electrochemical data shows that the ORR performance of FeCl 3 -intercalated GIC displays slight improvement where the onset potential reaches 0.77 V vs RHE in alkaline environments. However, expansion of the graphite and solvent-free incorporation of iron and nitrogen moieties resulted in a significant increase in ORR activity with onset potential to 0.89 V vs RHE, a maximum half-wave of 0.72 V vs RHE, and a limiting current of about 2.5 mA cm –2 . We anticipate that the use of near solvent-free processes that result in a high yield of catalysts along with the fundamental insight into the origin of electrochemical activity will tremendously impact the methodologies for developing next-generation ORR catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Two-Dimensional Conductive Ni-HAB as a Catalyst for the Electrochemical Oxygen Reduction Reaction

Catalytic systems whose properties can be systematically tuned via changes in synthesis conditions are highly desirable for the next-generation catalyst design and optimization. Herein, we present a two-dimensional (2D) conductive metal–organic framework consisting of M-N 4 units (M = Ni, Cu) and a hexaaminobenzene (HAB) linker as a catalyst for the oxygen reduction reaction. By varying synthetic conditions, we prepared two Ni-HAB catalysts with different crystallinities, resulting in catalytic systems with different electric conductivities, electrochemical activity, and stability. We show that crystallinity has a positive impact on conductivity and demonstrate that this improved crystallinity/conductivity improves the catalytic performance of our model system. Additionally, density functional theory simulations were performed to probe the origin of M-HAB’s catalytic activity, and they suggest that M-HAB’s organic linker acts as the active site with the role of the metal being to modulate the linker sites’ binding strength.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Improved Rate for the Oxygen Reduction Reaction in a Sulfuric Acid Electrolyte using a Pt(111) Surface Modified with Melamine

The feasible commercialization of alkaline, phosphoric acid and polymer electrolyte membrane fuel cells depends on the development of oxygen reduction reaction (ORR) electrocatalysts with improved activity, stability, and selectivity. The rational design of surfaces to ensure these improved ORR catalytic requirements relies on the so-called "descriptors" (e.g., the role of covalent and noncovalent interactions on platinum surface active sites for ORR). Here, we demonstrate that through the molecular adsorption of melamine onto the Pt(111) surface [Pt(111)-M ad ], the activity can be improved by a factor of 20 compared to bare Pt(111) for the ORR in a strongly adsorbing sulfuric acid solution. Additionally, the M ad moieties act as "surface-blocking bodies," selectively hindering the adsorption of (bi)sulfate anions (well-known poisoning spectator of the Pt(111) active sites) while the ORR is unhindered. This modified surface is further demonstrated to exhibit improved chemical stability relative to Pt(111) patterned with cyanide species (CN ad ), previously shown by our group to have a similar ORR activity increase compared to bare Pt(111) in a sulfuric acid electrolyte, with Pt(111)-M ad retaining a greater than ninefold higher ORR activity relative to bare Pt(111) after extensive potential cycling as compared to a greater than threefold higher activity retained on a CN ad -covered Pt(111) surface. We suggest that the higher stability of the Pt(111)-M ad interface stems from melamine's ability to form intermolecular hydrogen bonds, which effectively turns the melamine molecules into larger macromolecular entities with multiple anchoring sites and thus more difficult to remove.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Scalable Gas Diffusion Electrode Fabrication for Electrochemical CO 2 Reduction Using Physical Vapor Deposition Methods

Electrochemical CO 2 reduction (ECR) promises the replacement of fossil fuels as the source of feedstock chemicals and seasonal storage of renewable energy. While much progress has been made in catalyst development and electrochemical reactor design, few studies have addressed the effect of catalyst integration on device performance. Using a microfluidic gas diffusion electrolyzer, we systematically studied the effect of thickness and the morphology of electron beam (EB) and magnetron-sputtered (MS) Cu catalyst coatings on ECR performance. We observed that EB-Cu outperforms MS-Cu in current density, selectivity, and energy efficiency, with 400 nm thick catalyst coatings performing the best. Additionally, the superior performance of EB-Cu catalysts is assigned to their faceted surface morphology and sharper Cu/gas diffusion layer interface, which increases their hydrophobicity. Tests in a large-scale zero-gap electrolyzer yielded similar product selectivity distributions with an ethylene Faradaic efficiency of 39% at 200 mA/cm 2 , demonstrating the scalability for industrial ECR applications.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Ketjenblack-Supported and Unsupported ZrO 2 –ZrN Nanoparticle Systems for Enabling Efficient Electrochemical Nitrogen Reduction to Ammonia

Artificial N 2 fixation via the electrocatalytic nitrogen (N 2 ) reduction reaction (NRR) has been recently promoted as a rational route toward reducing energy consumption and CO 2 emission as compared with the traditional Haber–Bosch process. Nevertheless, optimizing NRR relies on developing highly efficient electrocatalysts. Herein, we report on the reliable and reproducible synthesis of two promising electrocatalysts in either the presence or absence of Ketjenblack (KB), namely, ZrO 2 –ZrN@KB and ZrO 2 –ZrN systems, synthesized through the nitriding of Zr. Both materials had never previously been considered for NRR, to the best of our knowledge. Nevertheless, both of these electrocatalysts incorporated a combination of tetragonal ZrO 2 , ZrON, and cubic ZrN and showed excellent activity and durability toward NH 3 formation. Moreover, the maximum NH3 production rate of 84.1 μg h –1 mg –1 at -0.7 V vs a reversible hydrogen electrode (RHE) was achieved with the ZrO 2 –ZrN electrocatalyst with an impressive Faradaic efficiency of 21.2% at -0.6 V vs RHE, indicating a high selectivity associated with the NRR. Additionally, the catalysts demonstrated excellent stability during the electrolysis process and recycling tests. Here we postulate that the combination of exposed active sites of ZrN and ZrO 2 likely contributes to the enhanced NRR performance attributed to ZrO 2 –ZrN.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Tuning the Electrocatalytic Oxygen Reduction Reaction Activity of PtCo Nanocrystals by Cobalt Concentration with Atomic-Scale Understanding

The development of a suitable catalyst for the oxygen reduction reaction (ORR) – the cathode reaction of proton exchange membrane fuel cells (PEMFC) – is necessary to push this technology towards widespread adoption. There have been substantial efforts to utilize bimetallic Pt-M alloys that adopt the ordered face-centered tetragonal (L10) phase in order to reduce the usage of precious metal, enhance the ORR performance, and improve catalyst stability. In this work, monodisperse Pt-Co nanocrystals (NCs) with well-defined size (4-5 nm) and cobalt composition (25-75 at%) were synthesized via colloidal synthesis. The transformation from the chemically disordered A1 (face-centered cubic, fcc) to the L10 phase was achieved via thermal annealing using both a conventional oven and a rapid thermal annealing process. The structure of the Pt-Co catalysts was characterized by a variety of techniques, including transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy in high-angle annular dark-field scanning transmission electron microscopy (STEM-EDS), small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), and inductively coupled plasma-optical emission spectrometry (ICP-OES). The effects of annealing temperature on the composition-dependent degree of ordering, and subsequent effect on ORR activity is described. This work provides insights regarding the optimal spatial distribution of elements at the atomic level to achieve enhanced ORR activity and stability.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2020

How Noninnocent Spectator Species Improve the Oxygen Reduction Activity of Single-Atom Catalysts: Microkinetic Models from First-Principles Calculations

Graphene-based single-atom catalysts are promising alternatives to platinum-based catalysts for fuel cell applications. Different transition metals have been screened using electronic structure methods by estimating onset potentials from the most endergonic elementary reaction step. Here, we calculate onset potentials for the oxygen reduction reaction on metal atoms embedded in N-substituted graphene di-vacancies by virtue of first-principles-informed microkinetic analysis. We find that for more oxophilic metals (Cr, Fe, Mn, and Ru), purely thermodynamic models systematically underestimate onset potentials. Furthermore, the oxophilic metals (Cr, Fe, Mn, and Ru) are oxidized under reaction conditions, leading to an increase in activity compared to their reduced state. Importantly, coadsorbed O m H n species actively participate in the reaction, which requires a dynamic treatment of spectator species. These findings highlight the limitations of thermodynamic analyses for electrocatalytic processes, which commonly assume the same oxidation state for each metal, and show that deviations between computational and experimental onset potentials cannot be solely attributed to the shortcomings of the electronic structure methods.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Pore-Edge Tailoring of Single-Atom Iron–Nitrogen Sites on Graphene for Enhanced CO 2 Reduction

Hosting atomically dispersed nitrogen-coordinated iron sites (Fe-N 4 ) on graphene offers unique opportunities for driving electrochemical CO 2 reduction reaction (CO 2 RR) to CO. However, the strong adsorption of *CO on the Fe-N 4 site embedded in intact graphene limits current density due to slow CO desorption process. Herein, we report how the manipulation of pore edges on graphene alters the local electronic structure of isolated Fe-N 4 sites and improves their intrinsic reactivity for prompting CO generation. We demonstrate that constructing holes on graphene basal plane to support Fe-N 4 can significantly enhance its CO 2 RR compared to the pore-deficient graphene-supported counterpart, exhibiting a CO Faradaic efficiency of 94% and a turnover frequency of 1630 h -1 at 0.58 V vs RHE. Mechanistic studies reveal that the incorporation of pore edges results in the downshifting of the d-band center of Fe sites, which weakens the strength of the Fe-C bond when the *CO intermediate adsorbs on edge-hosted Fe-N 4 , thus boosting the CO desorption and evolution rates. These findings suggest that engineering local support structure renders a way to design high-performance single-atom catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Rhombohedral Ordered Intermetallic Nanocatalyst Boosts the Oxygen Reduction Reaction

Low platinum-group-metal (PGM) ordered intermetallic catalysts have been considered one of the most promising candidates for catalyzing the oxygen reduction reaction (ORR) in fuel cells, but achieving the desired performances in terms of activity, durability, and cost is still a grand challenge for the fuel cell research field. While the cubic- and tetragonal-ordered (L1 2 and L1 0 phases) low-PGM nanocatalysts have been investigated extensively and have shown considerably improved durability and activity toward the ORR, so far, little is known about rhombohedral ordered L1 1 catalysts. Here, we report the synthesis of an L1 1 -ordered PtCu catalyst for the ORR. We demonstrate that by applying nitrogen (N) doping through a thermal treatment in an NH 3 gas, the activity and stability of the N-doped, rhombohedral ordered PtCu catalyst can be further enhanced, and the ORR mass and specific activities achieve nearly 5-fold and 4-fold enhancement in acidic media, respectively, relative to those of commercial Pt/C. In situ synchrotron X-ray absorption and pair-distribution-function measurements reveal that both the formation of the ordered intermetallic structure and N-doping synergistically improve the corrosion resistance of the PtCu catalyst by lowering the Cu diffusivity and introduce a compressive strain effect regulating the adsorption of oxygenated species on the Pt surface, thus accounting for the improved ORR kinetics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Effect of Support on Oxygen Reduction Reaction Activity of Supported Iron Porphyrins

In this work, we report the oxygen reduction reaction (ORR) activity in acid of an Fe porphyrin on different supports. While the activity is high (E 1/2 = 0.34 V vs RHE with n = 3.8) when the Fe porphyrin is adsorbed on XC72 (a graphitic carbon), this activity is much lower when the porphyrin is adsorbed on either MoS 2 (E 1/2 = -0.15 V vs RHE with n = 2.2) or g-C 3 N 4 (E 1/2 = -0.24 V vs RHE with n = 3.1). Electron paramagnetic resonance (EPR), X-ray absorption fine structure (XAFS), and magnetometry measurements show the electronic structure around the Fe center is the same for all three supports. Only the Fe porphyrin supported on XC72 exhibits a pH dependence in its ORR activity. This observation, coupled with the increased hydrophilicity of XC72 relative to the other supports, suggests that the support-electrolyte interaction controls the ORR activity. Modification of MoS 2 to increase its hydrophilicity results in a more active ORR catalyst.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Copper Single Atom-Triggered Niobia–Ceria Catalyst for Efficient Low-Temperature Reduction of Nitrogen Oxides

To reduce nitrogen oxide (NO x ) emission from diesel engines in the cold-start process benefitting the atmospheric environment, catalysts with superior low-temperature NO x removal efficiency are highly demanded. Herein, we report an efficient Nb 2 O 5 /CuO/CeO 2 (NbCuCe) oxide catalyst for the selective catalytic reduction (SCR) of NO x , showing much higher DeNO x activity below 200 °C, superior sulfur resistance, faster response, and much less NH 3 slip than the state-of-the-art Cu-CHA zeolite catalyst. Additionally, atomically dispersed Cu species facilitate the strong interaction between Cu and the Nb/Ce base catalyst, which significantly improves the low-temperature redox properties at Cu–O–Ce sites and NH 3 adsorption/activation at Nb–O–Cu sites, thus contributing to the superior SCR performance of NbCuCe at low temperatures. The developed NbCuCe catalyst is highly promising for efficient DeNO x from cold-start diesel engines and can be coupled with Cu-CHA to achieve a broad operation temperature window.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Swinging Hydrogen Evolution to Nitrate Reduction Activity in Molybdenum Carbide by Ruthenium Doping

A common challenge for electrochemical ammonia synthesis in an aqueous phase is the consumption of Faradaic charge by the competing hydrogen evolution reaction (HER), which reduces the Faradaic efficiency for the desired conversion, i.e., the nitrate reduction reaction (NO 3 RR) to ammonium. This problem is particularly severe when a single-phase catalyst is operated at high current limits, thus a cocatalyst system that works synergistically for hydrogen acquisition and deoxygenation is needed to promote NO 3 RR over HER. For this study, we select a well-known HER catalyst Mo 2 C and investigate how metal doping can switch its kinetics from HER-dominated to NO 3 RR-dominated pathways. At 3.8 wt % Ru doping of Mo 2 C, a 75% single pass conversion of nitrate (0.1 M) to ammonium in a 16 cm 2 flow electrolyzer was achieved, corresponding to an ammonium yield rate of 9.07 mmol h –1 at a full cell voltage of 2 V. As confirmed by DFT calculations and kinetic isotope experiments, ruthenium dopants in the matrix serve as the sink point for adsorbed hydrogen during NO 3 RR to promote the cooperative deoxygenation of *NO 3 and *NO 2 on the Ru–Mo cocatalytic site. Our study suggests that optimizing hydrogen acquisition and deoxygenation reactions in cocatalytic systems is an effective strategy for electrochemical synthesis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Interfacial Water Manipulation with Ionic Liquids for the Oxygen Reduction Reaction

The role that interfacial water plays in both promoting and inhibiting the electrochemical oxygen reduction reaction (ORR) remains somewhat unclear and controversial. Here, we use electroanalytical chemistry, spectroscopy, and microkinetic modeling to probe the impact of hydrophobic ionic liquid (IL) thin films on interfacial water structure and its role in promoting or inhibiting the ORR. Through the use of in situ ATR-SEIRAS, we find that the IL thin films limit the content of water at the interface and prevent the formation of hydrogen bond stabilized water organization. The impact of this exclusion of water on the promotion of the ORR is through the reduced coverage of OH ad spectator species. The decreased solvation of “active” OH ad species weakens its interaction with the catalyst surface, lowering the barrier to the last step in the ORR mechanism. This “destabilized” OH ad impact on ORR kinetics is confirmed through a microkinetic model. Furthermore, the results presented here highlight the mechanistic pathway through which hydrophobic ILs enhance ORR kinetics and point to pathways to both further improve this performance enhancement and the potential for integration of hydrophobic ILs into other technologically relevant elementary electrochemical reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Mechanistic Insights into Aldehyde Production from Electrochemical CO 2 Reduction on CuAg Alloy via Operando X-ray Measurements

CO 2 electrolysis converts the greenhouse gas CO 2 into valuable fuels and chemicals, such as carbon monoxide, ethylene, ethanol, etc. Currently, Cu is the only known monometallic catalyst capable of producing multicarbon products from electrochemical CO 2 reduction reaction (eCO2RR), while the poor selectivity limits its further use. It has been found that introducing Ag atoms into the Cu lattice can modulate product preference. However, the synergistic effects between Cu and Ag, and thus, the catalytic performance, are strongly influenced by catalyst morphology, electrolyzer configuration, reaction conditions, etc. Operando measurements can provide explicit information on the catalyst dynamic variation during the reaction, but their operation and analysis are challenging. Herein, we prepared CuAg multiphase alloy catalysts by magnetron sputtering, which allowed for investigating the intrinsic interaction between Cu and Ag. eCO2RR performance exhibited an improved selectivity toward carbonyls at the expense of hydrogen and hydrocarbons. The partially alloyed Cu and Ag phases were confirmed by operando X-ray diffraction. By means of combining operando X-ray measurements and density functional theory (DFT) calculations, the preferred carbonyl production is attributed to the reduced electron density and compressive strain of Cu due to Ag incorporation, which leads to a deeper d-band center and therefore weakened intermediate adsorption and oxophilicity. In conclusion, this work provides evidence of the intrinsic structural and electronic interaction between Cu and Ag during eCO2RR. The obtained information will facilitate the design of bi/multi-phase metallic or alloy electrocatalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗