Au-Pd Alloy Research Articles

Material Consequences of Hydrogen Dissolution in Palladium Alloys Observed from First Principles

Hydrogen embrittlement is one of the fundamental material science challenges to be faced under a potential “hydrogen economy”, as hydrogen will interact with the infrastructure for hydrogen production, storage, and transportation. While some embrittlement mechanisms have been proposed (especially for Fe), the behavior of dissolved hydrogen and impact on material properties is not fully understood in many systems relevant to hydrogen technologies. Here, hydrogen binding in pure Pd and alloys of Pd with Ag and Au was examined at a fundamental level from first principles in an attempt to elucidate how hydrogen-induced failure can be reduced in Pd alloys relevant to hydrogen production technologies. We show that PdAg and PdAu alloys (where the alloying metal is under 25%) likely suppress hydrogen-induced mechanical failure due to their reduced hydrogen solubility relative to pure Pd. This conclusion is based on our findings that alloying leads to higher vacancy stabilization and lower elastic constants upon hydrogen dissolution than for pure Pd but to unfavorable hydrogen dissolution beyond 25 at. %. The lowering of hydrogen solubility is strongly related to the combination of a lowering of the overall metal d-band center through alloy incorporation as well as changes to the metal Pauli repulsion factor, which is herein related to the metal matrix coupling element. Additionally, hydrogen loading and unloading were sequentially interrogated to mimic stress in storage materials. We find that permanent plastic deformation to the system is pronounced for alloyed systems, which in some cases made subsequent loading more favorable.

Structural and electronic feature evolution of Au-Pd bimetallic catalysts supported on graphene and SiO2 in H2 and O2

The structure and electronic feature evolution of graphene (Gr)- and SiO2-supported Au-Pd bimetallic nanoparticles (NPs) in H2 and O2 at different temperatures were investigated with a series of techniques and DFT calculation method. It was found that a uniform Au-Pd alloy nanostructure was formed on Gr, while a Au@Pd core-shell structure was generated on SiO2. The formation of Au-Pd alloy nanostructure on Gr originates from a strong s-p-d hybridization among Au 5d6s, Pd 4d and Gr C 2p, which greatly facilitates the electron transfer among Au, Pd and Gr and enhances the reduction of palladium species. The higher stability of the geometric and electronic structures of Au-Pd NPs on Gr than on SiO2 in both H2 and O2 atmospheres below 100 °C results from the fact that Gr could timely supplement the electrons transferring to O2 from metallic species in O2-treatment process, but play a contrary role in H2-treatment process. Such unique geometric and electronic structures endow Au-Pd/Gr show higher catalytic activity than Au-Pd/SiO2 in selective oxidation of methanol to methyl formate. A further investigation of catalytic mechanism reveals that the activation of O2 is dominated by the methanol-assisted way on Au and Au-Pd alloy NPs, whereas the direct dissociation of O2 mainly occurs on Pd and Au@Pd NPs.

Near-Infrared Light-Triggered Porous AuPd Alloy Nanoparticles To Produce Mild Localized Heat To Accelerate Bone Regeneration.

The treatment of massive bone defects is still a significant challenge for orthopedists. Here we have engineered synthetic porous AuPd alloy nanoparticles (pAuPds) as a hyperthermia agent for in situ bone regeneration through photothermal therapy (PTT). After being swallowed by cells, pAuPds produced a mild localized heat (MLH) (40-43 °C) under the irradiation of a near-infrared laser, which can greatly accelerate cell proliferation and bone regeneration. Almost 97% of the cranial defect area (8 mm in diameter) was covered by the newly formed bone after 6 weeks of PTT. RNA sequencing analysis was used to obtain insight into the molecular mechanism of the MLH on cell proliferation and bone formation. These results demonstrated that the Wnt signaling pathway was involved in the MLH. This Letter provides a unique strategy with mild heat stimulation and high efficiency for in situ bone regeneration.

Surface Plasmon Resonant Gold-Palladium Bimetallic Nanoparticles for Promoting Catalytic Oxidation

AbstractColloidal gold-palladium (Au-Pd) bimetallic nanoparticles were used as catalysts to study the ethanol (EtOH) photo-oxidation cycle, with an emphasis towards driving carbon-carbon (C-C) bond cleavage at low temperatures. Au-Pd bimetallic alloy and core-shell nanoparticles were prepared to synergistically couple a plasmonic absorber (Au) with a catalytic metal (Pd) with composite optical and catalytic properties tailored towards promoting photocatalytic oxidation. Catalysts utilizing metals that exhibit localized surface plasmon resonance (SPR) can be harnessed for light-driven enhancement for small molecule oxidation via augmented photocarrier generation/separation and photothermal conversion. The coupling of Au to Pd in an alloy or core-shell nanostructure maintains SPR-induced charge separation, mitigates the poisoning effects on Pd, and allows for improved EtOH oxidation. The Au-Pd nanoparticles were coupled to semiconducting titanium dioxide photocatalysts to probe their effects on plasmonically-assisted photocatalytic oxidation of EtOH. Complete oxidation of EtOH to CO2 under solar simulated-light irradiation was confirmed by monitoring the yield of gaseous products. Bimetallics provide a pathway for driving desired photocatalytic and photoelectrochemical reactions with superior catalytic activity and selectivity.

Au-Pd alloy nanoparticles catalyze the colorimetric detection of hydrazine with methylene blue

A colorimetric detection of hydrazine using AuPd alloy nanoparticles (NPs) as catalyst is described, in which methylene blue (methylthioninium chloride) acts as a redox indicator. The sensing system with AuPd NPs shows a rapid response at room temperature, leading to a color change within a few minutes, which is not achievable with Au or Pd NPs. A linear change in absorbance versus hydrazine concentration ranging from 0.1 to 5.0 mM can be obtained with a detection limit of ~4 × 10−4 M. The catalytic activity of the AuPd NPs in the reaction can be attributed to the electronic inductive effect by Au on Pd in the alloy NPs.

Alloying of gold with palladium: An effective strategy to improve catalytic stability and chlorine-tolerance of the 3DOM CeO2-supported catalysts in trichloroethylene combustion

The three-dimensionally ordered macroporous (3DOM) CeO2-supported Au–Pd alloys (xAuPdy/3DOM CeO2, x is the total loading (wt%) of Au and Pd, and y is the Pd/Au molar ratio) were synthesized using the polymethyl methacrylate-templating and polyvinyl alcohol-protected reduction methods. The samples were characterized by a number of analytical techniques, and their catalytic performance was evaluated for the combustion of trichloroethylene (TCE). It is found that the xAuPdy/3DOM CeO2 samples displayed a good-quality 3DOM architecture, and the noble metal nanoparticles (NPs) with a size of 3–4 nm were uniformly dispersed on the skeleton surface of 3DOM CeO2. Among all of the samples, 2.85AuPd1.87/3DOM CeO2 exhibited the highest catalytic activity, with the temperature at a TCE conversion of 90% (T90%) being 415 °C at a space velocity of 20,000 mL/(g h). Furthermore, the 2.85AuPd1.87/3DOM CeO2 sample possessed the lowest apparent activation energy (33 kJ/mol), excellent catalytic stability, and good moisture- and chlorine-tolerant behaviors. Alloying of Au with Pd changed the pathway of TCE oxidation and reduced formation of perchloroethylene. We conclude that the excellent catalytic performance for TCE combustion of 2.85AuPd1.87/3DOM CeO2 was associated with the highly dispersed AuPd1.87 alloy NPs, high adsorbed oxygen species concentration, good low-temperature reducibility, and strong interaction between AuPd1.87 NPs and 3DOM CeO2 as well as the high-quality 3DOM structure and high surface acidity.

Dehydrogenative Aromatization Reactions by Supported Pd or Au-Pd Alloy Nanoparticles Catalysts

Dehydrogenative Aromatization Reactions by Supported Pd or Au-Pd Alloy Nanoparticles Catalysts

Formation of PdO on Au–Pd bimetallic catalysts and the effect on benzyl alcohol oxidation

A series of catalysts consisting of gold–palladium bimetallic nanoparticles (Au–Pd NPs in the range of 1–6 nm) anchored on foamlike mesoporous silica were used for the aerobic oxidation of benzyl alcohol. A remarkable synergistic effect was observed on these Au–Pd NP catalysts prepared by a one-pot method. Both experimental and theoretical study revealed a close relationship between the surface PdO species on the catalysts and their catalytic performance; that is, higher surface PdO content leads to lower catalytic activity. The surface content of PdO species on the catalysts could be tuned by controlling the Au/Pd ratios, because the formation of Au–Pd alloy NPs and electron transfer between surface Au and Pd atoms prevented the oxidation of surface Pd and retarded the formation of PdO species. An optimal Au/Pd ratio of 1/4.5 on the foamlike mesoporous silica support was obtained, with nearly no surface PdO species formed, and resulted in the highest benzyl alcohol conversion of 96%. The bimetallic Au–Pd catalysts exhibited much higher catalytic activity for benzyl alcohol oxidation (TOF = 50,000–60,000 h−1) than the monometallic Pd catalyst (TOF = 12,500 h−1), on which surface Pd is easily oxidized to PdO. These results provide direct evidence for the synergistic effect of Au–Pd bimetallic catalysts in benzyl alcohol oxidation.

Structure-Property-Performance Relationship of Ultrathin Pd-Au Alloy Catalyst Layers for Low-Temperature Ethanol Oxidation in Alkaline Media.

Pd-containing alloys are promising materials for catalysis. Yet, the relationship of the structure-property performance strongly depends on their chemical composition, which is currently not fully resolved. Herein, we present a physical vapor deposition methodology for developing PdxAu1-x alloys with fine control over the chemical composition. We establish direct correlations between the composition and these materials' structural and electronic properties with its catalytic activity in an ethanol (EtOH) oxidation reaction. By combining X-ray diffraction (XRD) and X-ray photelectron spectroscopy (XPS) measurements, we validate that the Pd content within both bulk and surface compositions can be finely controlled in an ultrathin-film regime. Catalytic oxidation of EtOH on the PdxAu1-x electrodes presents the largest forward-sweeping current density for x = 0.73 at ∼135 mA cm-2, with the lowest onset potential and largest peak activity of 639 A gPd-1 observed for x = 0.58. Density functional theory (DFT) calculations and XPS measurements demonstrate that the valence band of the alloys is completely dominated by Pd particularly near the Fermi level, regardless of its chemical composition. Moreover, DFT provides key insights into the PdxAu1-x ligand effect, with relevant chemisorption activity descriptors probed for a large number of surface arrangements. These results demonstrate that alloys can outperform pure metals in catalytic processes, with fine control of the chemical composition being a powerful tuning knob for the electronic properties and, therefore, the catalytic activity of ultrathin PdxAu1-x catalysts. Our high-throughput experimental methodology, in connection with DFT calculations, provides a unique foundation for further materials' discovery, including machine-learning predictions for novel alloys, the development of Pd-alloyed membranes for the purification of reformate gases, binder-free ultrathin electrocatalysts for fuel cells, and room temperature lithography-based development of nanostructures for optically driven processes.

AuPd-Fe3 O4 Nanoparticle-Catalyzed Synthesis of Furan-2,5-dimethylcarboxylate from 5-Hydroxymethylfurfural under Mild Conditions.

Efficient one-pot oxidative esterification of 5-hydroxymethylfurfural (HMF) to furan-2,5-dimethylcarboxylate (FDMC) was achieved under extremely mild reaction conditions by using AuPd alloy nanoparticles (NPs) supported on Fe3 O4 . A high yield of FDMC (92 %) was obtained at room temperature under atmospheric O2 . The reaction proceeded through the synergistic effects of the AuPd heterobimetallic catalyst system. The most effective molar ratio of noble metal contents for HMF oxidation was 1.00:1.18. If Au-Fe3 O4 NPs were used as the catalyst, selective synthesis of 5-hydroxymethylfuroic acid methyl ester (HMFE) was achieved. Additionally, the AuPd-Fe3 O4 catalyst could be successfully reused.

Direct Comparison of PdAu Alloy Thin Films and Nanoparticles upon Hydrogen Exposure.

Nanostructured metal hydrides are able to efficiently detect hydrogen in optical sensors. In the literature, two nanostructured systems based on metal hydrides have been proposed for this purpose each with its own detection principle: continuous sub-100 nm thin films read out via optical reflectance/transmittance changes and nanoparticle arrays for which the detection relies on localized surface plasmon resonance. Despite their apparent similarities, their optical and structural response to hydrogen has never been directly compared. In response, for the case of Pd1–yAuy (y = 0.15–0.30) alloys, we directly compare these two systems and establish that they are distinctively different. We show that the dissimilar optical response is not caused by the different optical readout principles but results from a fundamentally different structural response to hydrogen due to the different nanostructurings. The measurements empirically suggest that these differences cannot be fully accounted by surface effects but that the nature of the film–substrate interaction plays an important role and affects both the hydrogen solubility and the metal-to-metal hydride transition. In a broader perspective, our results establish that the specifics of nanoconfinement dictate the structural properties of metal hydrides, which in turn control the properties of nanostructured devices including the sensing characteristics of optical hydrogen sensors and hydride-based active plasmonic systems.

Plasmonic AuPd-based Mott-Schottky photocatalyst for synergistically enhanced hydrogen evolution from formic acid and aldehyde

Plasmonic AuPd alloy nanoparticles supported on super small carbon nitride nanospheres (AuxPdy/CNS) for the design of Mott-Schottky catalysts were successfully synthesized and further applied for the photocatalytic hydrogen evolution from formic acid. A high turnover frequency (TOF) value of 1017.8 h−1 was obtained for the AuPd/CNS catalyst under visible-light irradiation (λ > 420 nm) at 298 K. XPS analysis, photoelectrochemical characterization and density functional theory (DFT) calculation indicate that the remarkable photocatalytic activities are mainly attributed to the optimized electronic structure of Pd in the AuPd/CNS composite resulting from the alloying, plasmonic and Mott-Schottky effects. These effects can efficiently accelerate the electron transfer from photoresponsive super small carbon nitride nanospheres and plasmonic Au to the active Pd sites. We also infer that the alloying effect is the main factor on the high activity, which is mainly due to weakened adsorption of hydrogen atoms on Pd sites according to the DFT calculation. Moreover, the Mott-Schottky AuPd/CNS catalyst presents a good universality for the photocatalytic hydrogen evolution from a series of aldehyde aqueous solutions.

High-throughput micropatterning of plasmonic surfaces by multiplexed femtosecond laser pulses for advanced IR-sensing applications

Tightly focused, highly spatially multiplexed femtosecond laser pulses, coming at sub-MHz repetition rates, were used to mask-less pattern thin plasmonic films film at ultrafast rates, approaching 25 million of microelements per second. For this purpose, the initial pulses were multiplexed by fused silica diffractive optical elements into linear arrays of 31, 51 and 101 circular light spot and then scanned over the films by a galvanometric scanner through a long-focus objective or high-NA aspherical lens. These optical scheme and 5-μJ pulse energy supported the only 31- and 51-beam micro-patterning, with the corresponding aperture, field-of-view and sub-100 nJ energetic limitations for the laser processing of the film. The resulting large (~105–106 holes per array) arrays of micro-holes of variable diameters and periods in thin films of different thickness and diverse plasmonic materials - Ag, Cu, Al and Au-Pd alloy (80%/20%) - were for the first time systematically characterized in the broad IR-range (1.5–25 μm) in terms of plasmonic effects in extraordinary optical transmission, indicating for the increasing wavenumber a smooth transition from the common Bethe-Bouwkamp transmission to its plasmon-enhanced analogue, ending up with common geometrical (wave-guide-like) transmission. Finally, promising label- and luminescence-free laboratory-scale, robust and high-sensitivity sampling of chemicals and biosamples via plasmonic and chemical contributions, uneven and structurally-sensitive regarding different functional groups of the model analyte molecules and band structure of the plasmonic metal, was demonstrated for the large IR-sensing arrays of micro-holes in plasmonic films, with the obvious perspectives for down-scaling of sensing elements for vis-IR surface-enhanced spectroscopies.

Highly active carbon nanotube supported PdAu alloy catalysts for ethanol electrooxidation in alkaline environment

At present, ethanol electrooxidation study is performed on CNT supported Pd and PdAu catalysts to investigate the effect of Au addition to Pd towards the ethanol electrooxidation activity. NaBH4 reduction method is employed for the synthesis of Pd/CNT, Pd90Au10/CNT, Pd90Au10/CNT, Pd70Au30/CNT, Pd50Au50/CNT, and Pd40Au60/CNT catalysts. These catalysts are characterized via advanced surface analytical techniques namely N2 adsortion-desoprtion measurements,X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM). The characterization results revealed that Pd90Au10/CNT has 205.42 m2/g and 1.18 cm3/g BET surface area (m2/g) and pore volume (cm3/g), respectively. On the other hand, XRD and XPS results revealed that the electronic state of Pd90Au10/CNT catalyst changed by Au addition to Pd. TEM and HRTEM and elemental mapping results reveal that Pd and Au is homogeneously dispersed and alloying of Pd and Au is clearly observed, in agreement with the XRD and XPS results. Ethanol electrooxidation measurements in alkaline environment are performed by Cyclic Voltammetry (CV), Chronoamperometry (CA), Electrochemical impedance spectroscop (EIS) techniques. Pd90Au10/CNT displayed the highest specific and mass activity. The synergistic effect between Pd and Au at optimized metal ratio was utilized to obtain an improvement in specific activity. Furthermore, Pd90Au10/CNT showed the lowest charge transfer resistance (Rct) and a long term stability. As a result, it is clear that PdAu catalyst is a promising catalyst for Alkaline Direct Ethanol Fuel Cells.

A Gold–Palladium Nanoparticle Alloy Catalyst for CO Production from CO2 Electroreduction

Electrochemical CO2 reduction reaction (CO2RR) is a promising technology for combining CO2 reutilization and renewable electricity storage. For economic feasibility, better catalysts are required to overcome current limitations such as high overpotentials, poor faradaic efficiencies (FEs), and low current densities. Herein, size‐ and composition‐controlled gold (Au)–palladium (Pd) bimetallic alloy nanoparticles prepared by a metal vapor synthesis technique together with the monometallic Au and Pd equivalent materials are investigated. X‐ray diffraction and high‐angle annular dark‐field scanning transmission electron microscopy energy‐dispersive X‐ray spectroscopy analyses confirm the Au–Pd alloy formation with an average atomic ratio of 76 Pd wt% and 24 Au wt%. These bimetallic and the monometallic catalysts are characterized and tested for the electroreduction of CO2 in electrochemical cells and also in a complete CO2 electrolysis cell. Analysis of the reduction products shows a 100% CO2RR selectivity for CO. The FE for CO with respect to H2 as high as 90% is obtained with Au–Pd/C by tuning the electrode structure. The Au/C and Pd/C catalysts also show a better selectivity for CO with no evidence of other CO2RR products. The Au–Pd alloy formation improves the FE of Pd for CO by suppressing the parasitic H2 evolution reaction.

Microfluidically synthesized Au, Pd and AuPd nanoparticles supported on SnO2 for gas sensing applications

Monometallic Au and Pd nanoparticles (NPs) and homogeneous AuPd nanoalloy particles were synthesized in a continuous flow of reactants (HAuCl4, K2PdCl4, NaBH4 and polyvinylpyrrolidone (PVP)) using a microfluidic reactor with efficient micromixers. The obtained ultrasmall NPs were subsequently deposited onto SnO2 supports with different surface area (32.7 and 3.6 m2 g−1). Samples with 1.0 and 0.1 wt.% metal loading were prepared. After calcination at 380 °C for 1 h the supported NPs aggregated to some extent. SnO2 supported AuPd nanoalloys with low (0.1 wt.%) metal loadings showed the smallest NP diameters (˜ 5–7 nm) and the narrowest size distribution among the samples. The gas sensing performance of the materials was investigated at 300 °C in four different gas atmospheres containing either CO, CH4, ethanol or toluene using dry and humid conditions. They exhibited a distinct variation in the response patterns and selectivity toward the test gases depending on composition and metal loading: Au increased the sensor signals compared to pristine SnO2 in all cases and decreased the interference of water vapor; the supported Pd NPs showed a weak response to toluene, strong sensitivity in CO sensing and slightly better response in ethanol sensing in humid air compared to dry air. However, they showed a high selectivity toward CH4 when used in dry air; AuPd alloy particles provided lower sensor signals compared to pristine SnO2 and no remarkable CH4 selectivity, in contrast to the Pd system. Operando diffuse reflectance infrared Fourier-transformed spectroscopy (DRIFTS) and DC-resistance measurements indicate a strong band bending in the case of Pd and AuPd NPs, whereas in the case of Au no band bending occured, indicating a strong electronic interaction between the support and Pd-containing NPs (Fermi-level control mechanism), and a weak electronic interaction between SnO2 and Au NPs (spill-over mechanism).

Thermal properties and segregation phenomena in transition metals and alloys: modeling based on modified cohesive-energies

In spite of free-atom electronic-relaxation contributions to transition-metal cohesive-energies, numerous studies have misused the latter instead of using the solid-state interatomic bond-energy in modeling bulk and surface properties. This work reveals that eliminating the free-atom contributions from experimental cohesive-energies leads to highly accurate linear correlations of the resultant bond-energies with melting temperatures and enthalpies, as well as with inverse thermal-expansion coefficients, specifically for the fcc transition-metals. Likewise, predictions of surface segregation phenomena in Cu–Pd and Au–Pd alloys on the basis of the modified energetics are in much better agreement with reported low-energy ion scattering spectroscopy (LEISS) experimental results, as compared to the use of cohesive-energy values. A last demonstration of the problem and its solution involves the significant impact of the modification on segregation (separation) phase transitions in Cu–Ni model nanoparticles.

Cyclic Voltammetry Characterization of Au, Pd, and AuPd Nanoparticles Supported on Different Carbon Nanofibers

Three types of carbon nanofibers (pyrolytically stripped carbon nanofibers (PS), low-temperature heat treated carbon nanofibers (LHT), and high-temperature heat treated carbon nanofibers (HHT)) with different graphitization degrees and surface chemistry have been used as support for Au, Pd, or bimetallic AuPd alloy nanoparticles (NPs). The carbon supports have been characterized using Raman, X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). Moreover, the morphology of the metal nanoparticles was investigated using transmission electron microscopy (TEM) and CV. The different properties of the carbon-based supports (particularly the graphitization degree) yield different electrochemical behaviors, in terms of potential window widths and electrocatalytic effects. Comparing the electrochemical behavior of monometallic Au and Pd and bimetallic AuPd, it is possible to observe the interaction of the two metals when alloyed. Moreover, we demonstrate that carbon surface has a strong effect on the electrochemical stability of AuPd nanoparticles. By tuning the Au-Pd nanoparticles’ morphology and modulating the surface chemistry of the carbon support, it is possible to obtain materials characterized by novel electrochemical properties. This aspect makes them good candidates to be conveniently applied in different fields.

Ultrathin Pd-Au Shells with Controllable Alloying Degree on Pd Nanocubes toward Carbon Dioxide Reduction.

Electrocatalytic reduction of carbon dioxide (CO2ER) to reusable carbon resources is a significant step to balance the carbon cycle. This Communication describes a seed-mediated growth method to synthesize ultrathin Pd-Au alloy nanoshells with controllable alloying degree on Pd nanocubes. Specifically, Pd@Pd3Au7 nanocrystals (NCs) show superior CO2ER performance, with a 94% CO faraday efficiency (FE) at -0.5 V vs reversible hydrogen electrode and approaching 100% CO FE from -0.6 to -0.9 V. The enhancement primarily originates from ensemble and ligand effects, i.e., appropriately proportional Pd-Au sites and electronic back-donation from Au to Pd. In situ attenuated total reflection infrared spectra and density functional theory calculations clarify the reaction mechanism. This work may offer a general strategy for the synthesis of bimetallic NCs to explore the structure-activity relationship in catalytic reactions.

Suppressing H2 Evolution and Promoting Selective CO2 Electroreduction to CO at Low Overpotentials by Alloying Au with Pd

CO 2 electroreduction is a promising technology to produce chemicals and fuels from renewable resources. Polycrystalline and nanostructured metals have been tested extensively while less effort has been spent on understanding the performance of bimetallic alloys. In this work, we study compositionally variant, smooth Au-Pd thin film alloys to discard any morphological or mesoscopic effect on the electrocatalytic performance. We find that the onset potential of CO formation exhibits a strong dependence on the Pd content of the alloys. Strikingly, palladium, a hydrogen evolution catalyst with reasonable exchange current density, suppresses hydrogen evolution when alloyed with gold in the presence of CO 2 . Cyclic voltammetry, in situ surface enhanced infrared absorption spectroscopy, and potential-dependent online product analysis strongly suggest that by alloying Au with Pd a significant increase in the surface coverage of adsorbed CO occurs with increasing Pd content at low overpotentials (e.g., approximately -0.35 V vs RHE). Such an increase in CO coverage suppresses H 2 evolution due to the lack of vacant active sites. Moreover, the overall increase in the binding energy with the CO 2 intermediates gained with the addition of Pd increases the CO production at low overpotentials, where polycrystalline Au suffers from poor CO 2 adsorption and poor selectivity for CO production. These results show that promising CO 2 reduction electrode materials (e.g., Au) can be alloyed not only to tune the catalyst's activity but also to deliberately decrease the availability of surface sites for competitive H 2 evolution.