Au Sites Research Articles

Hydrogen Evolution Reaction on AuNi Surface Alloy Formed on Single Crystal Au Electrodes

AbstractThe hydrogen evolution reaction (HER) on Au with high chemical stability is activated by alloying it with Ni. We evaluated the HER activity of the AuNi surface alloy prepared at different alloying temperatures on single‐crystal Au electrodes in 0.05 M H2SO4. The potential cycle, including the region of Ni oxidative dissolution, further enhanced the HER activity by dealloying Ni, and the activity depended on the surface structure of the Au substrate in the following order: AuNi/Au(100)<AuNi/Au(111)<AuNi/Au(110). The surface structure and atomic composition were investigated using X‐ray photoelectron spectroscopy and surface X‐ray diffraction. Surface structural analysis revealed that the dissolution of Ni from the AuNi surface‐alloy layer resulted in a decrease in the atomic occupancy of the topmost surface layer. Ni dealloying creates low‐coordination Au sites on the AuNi surface alloy, which activates the HER.

Improving oxidation removal of toluene in plasma coupling perovskite catalysts system by constructing Au sites on a La0.5Ce0.5CoO3-δ

Plasma-catalysis technique is a promising approach to control air pollution caused by volatile organic compounds (VOCs). Perovskite-type oxides have excited much interest in constructing plasma-catalytic system for the oxidation removal of VOCs owing to their flexible electronic structure, alterable geometry, unique catalytic properties and high stability. However, the perovskites commonly suffer from low surface area and small amounts of active surface sites because of their high synthesis temperature, which limits the synergism between the perovskites and plasma and thus decreases the performance of plasma-catalytic oxidation of VOCs. Here we show that the oxidation removal of toluene (typical refractory VOCs) in the plasma-catalytic system is improved by constructing Au sites on a perovskite of La0.5Ce0.5CoO3-δ (Au/La0.5Ce0.5CoO3-δ). Compared with plasma-catalytic systems integrated by LaCoO3 or La0.5Ce0.5CoO3-δ, coupling the Au/La0.5Ce0.5CoO3-δ with plasma enables the boost of toluene conversion and CO2 selectivity, but suppresses the generation of secondary pollutants (O3 and NOx). The calculation of apparent activation energy (Ea) demonstrates that the plasma-catalytic system integrated by Au/La0.5Ce0.5CoO3-δ obtains lower Ea of 6.9 kJ/mol than those integrated by LaCoO3 (9.5 kJ/mol) and La0.5Ce0.5CoO3-δ (8.1 kJ/mol) as well as plasma alone (15.0 kJ/mol), confirming a favorable toluene oxidation process in the plasma coupling Au/La0.5Ce0.5CoO3-δ system. Catalyst characterizations, discharge diagnosis and density functional theory calculations suggest that depositing Au on the La0.5Ce0.5CoO3-δ render the favorable gas and surface reactions for toluene oxidation in the plasma-catalytic system and thus a strong synergism between the perovskites and plasma, by modulating the discharge mode and creating large numbers of highly active Auδ+-Oδ--Ce interfacial sites on the surface of La0.5Ce0.5CoO3-δ.

Site Communication in Direct Formation of H2O2 over Single-Atom Pd@Au Nanoparticles

Single atom alloy catalysts offer possibilities to obtain turnover frequencies and selectivities unattainable by their monometallic counterparts. One example is direct formation of H2O2 from O2 and H2 over Pd embedded in Au hosts. Here, a first-principles-based kinetic Monte Carlo approach is developed to investigate the catalytic performance of Pd embedded in Au nanoparticles in an aqueous solution. The simulations reveal an efficient site separation where Pd monomers act as active centers for H2 dissociation, whereas H2O2 is formed over undercoordinated Au sites. After dissociation, atomic H may undergo an exothermic redox reaction, forming a hydronium ion in the solution and a negative charge on the surface. H2O2 is preferably formed from reactions between dissolved H+ and oxygen species on the Au surface. The simulations show that tuning the nanoparticle composition and reaction conditions can enhance the selectivity toward H2O2. The outlined approach is general and applicable for a range of different hydrogenation reactions over single atom alloy nanoparticles.

Au3Pd1 intermetallic compound as single atom catalyst for formic acid decomposition with highly hydrogen selectivity

Developing efficient catalysts for formic acid decomposition has been studied extensively. Herein, the Au3Pd1 intermetallic compound is designed as a single atom catalyst for the dehydrogenation of formic acid. By using density functional theory calculations, the thermodynamic stability, electronic structure, and reaction mechanism for the Au3Pd1 catalyst are systematically investigated, and the surface charge polarization and atom-ordered arrangement were confirmed to play an important role in the efficient formic acid dehydrogenation. The special positively charged Pd single atom on the Au3Pd1 surface becomes the adsorption site of HCOO− and the reaction site for formic acid decomposition. The nearby Au sites suppress the C–O bond cleavage due to their weak interaction with CO∗ and OH∗. As a result, the HCOO− dehydrogenation pathway is predominant on the Pd single atomic sites and the CO formation is well inhibited. This intermetallic-based catalyst can be extended to other systems and provided general guidance for efficient catalyst design.

On the Friction Behavior of SiO2 Tip Sliding on the Au(111) Surface: How Does an Amorphous SiO2 Tip Produce Regular Stick-Slip Friction and Friction Duality?

Friction behaviors of an amorphous SiO2 tip sliding on the Au(111) surface in atomic force microscopy (AFM) are investigated through molecular dynamics (MD) simulations. We observed a regime of extremely low, close-to-zero friction at low normal loads with clear stick-slip friction signals. The friction is almost independent of the applied normal load below a threshold value. However, above this loading threshold, friction can remain low or increase sharply. Such an unexpected friction duality is attributed to the high probability of defect formation at the sliding interface that can induce plowing friction in a high-friction state. The energy difference between the low-friction state and the high-friction state is surprisingly low, which is comparable to kT (∼25 meV) at room temperature. These findings are consistent with previous AFM friction measurements using silicon AFM tips. Further MD simulations show that one can always use an amorphous SiO2 tip to image the crystalline surface with regular stick-slip friction signals. This is largely due to the fact that there is always a small fraction of contacting Si and O atoms at the sliding interface that are sitting on the relatively stable, close-to-hollow sites of the crystalline Au(111) surface during the stick stage; thus, they are capable of sampling local energy minima. We anticipate that regular stick-slip friction can be achieved even in the intermediate loading range, so long as the low-friction state is maintained when friction duality occurs.

TS-1 with Abundant Micropore Channel-Supported Au Catalysts toward Improved Performance in Gas-Phase Epoxidation of Propylene

The gas-phase propylene epoxidation reaction catalyzed by Au/TS-1 has attracted great attention due to its clean and efficient merits. However, high conversion of propylene (>10%) and high selectivity of propylene oxide (PO) (>90%) often cannot be obtained at the same time. Although a variety of TS-1 supports with different microstructures have been developed to improve the catalytic performance, few have met the above criteria. In this work, we have reported a silane-assisted strategy to prepare TS-1-CTES zeolites containing abundant micropore channels, which showed both high propylene conversion (13.3%) and high PO selectivity (92.7%). The silane, (3-chloropropyl) triethoxysilane (CTES), not only participates in constructing the MFI framework but also serves as a spatial filling agent to build secondary micropore channels. Ar physisorption characterization exhibited the increased micropore volume and surface area of the as-synthesized TS-1-CTES, which benefit molecule diffusion. XPS results showed an enriched Ti concentration on the surface of TS-1-CTES and a decreased electron density of Ti atoms. A few more Au nanoparticles were proved to be distributed inside the TS-1-CTES crystal compared with those inside TS-1. The optimized distribution of Au and Ti active sites in Au/TS-1-CTES enhanced their synergistic catalytic effects. The PO formation rate remained relatively stable for 24 h, superior to traditional Au/TS-1. The construction of a micropore-rich TS-1 structure opens a way for the reasonable design and manufacture of the Au/TS-1 catalyst, for the gas-phase epoxidation of propylene.

Regulating the surface Au sites of Au/TiO2 catalyst for achieving co-oxidation of HCHO and CO at room temperature

While supported Au catalyst is active for formaldehyde (HCHO) or CO oxidation alone at room temperature, it has not been reported hitherto to efficiently catalyze co-oxidation of HCHO and CO. In this work, we prepared the fresh Au/TiO2 (Au/Ti-F) and the Au/Ti-O by pretreating Au/Ti-F at 300 °C under O2 atmosphere. The Au/Ti-F is only active for HCHO oxidation during HCHO and CO co-oxidation, while the Au/Ti-O shows high efficiency for both HCHO and CO oxidation, achieving 100 % conversions at room temperature. Detailed characterization and DFT calculation indicate that only the Au-Ti interface sites were exposed on Au/Ti-F because other Au sites on Au NPs were covered by Au(OH)n (0 <n < 3). Over Au/Ti-O, besides the active sites at the Au-Ti interface, the metallic Au sites away from the interface were formed during the high-temperature treatment. HCHO oxidation occurs at the Au-Ti interface sites while CO oxidation occurs at the metallic top Au sites; hence high activity for HCHO and CO co-oxidation was achieved over Au/Ti-O. The obtained insight into the dual Au sites will benefit future design of supported Au catalysts.

Dynamic Monitoring of the Structural Evolution of Au@Pd under Electrochemistry

Core–shell nanocatalysts have shown superior catalytic activity than monometallic catalysts. However, these metastable materials are susceptible to structural changes during catalysis. Comprehending the evolution of surface sites and their stability under different reaction conditions is crucial for designing durable and highly active core–shell nanocatalysts. Herein, structural transformation of the atomic layer thickness of Pd shells on Au nanocubes in different electrolytes at various electrochemical windows was investigated by a combination of cyclic voltammetry (CV), surface-enhanced Raman spectroscopy (SERS) of adsorbed probe molecules, and elemental analysis. Pd sites are stable under basic and neutral conditions but experience severe structure evolution under acidic conditions. Pd atoms that are directly coordinated by Au atoms, upon oxidation at evaluated potential, transform into Pd ions via the reaction with H+ which would also be adsorbed on the Au sites. These Pd ions are easily coreduced with the formed Au ions into surface alloys in the backward CV scan. In contrast, Pd atoms in the thick Pd overlayer (>1 monolayer) are likely to dissolute into the electrolyte solution and leach. SERS revealed that the change of Pd sites primarily occurred at contiguous Pd sites and isolated Pd sites were relatively stable. This evolution mechanism provides new insight into the rational design of efficient and stable catalysts and is expected to promote further application of core–shell nanocatalysts.

Synergistic assembly of gold and copper-iron oxide nanocatalysts to promote the simultaneous depletion of glucose and glutathione

Glucose and glutathione (GSH) are key biomolecules for the regulation and growth of tumor cells. The use of inorganic nanocatalysts in biomedicine to target and deplete such specific molecules represents a novel and promising strategy against cancer. In this work, we present a ternary assembled nanohybrid based on Au and CuFe2O4 with the capability to simultaneously deplete glucose and GSH and generate reactive oxidative species (ROS) in a cascade process. We describe an example of a synergistic heterogeneous nanoarchitecture able to maintain the glucose oxidase-like activity of Au while preventing its deactivation in the presence of GSH. Au sites remain active due to the rapid response of the Cu–Fe co-catalyst to deplete GSH levels. This example of hybrid heterostructure represents an appealing alternative with dual-activity within the tumor microenvironment (TME) for potential anticancer therapy.

Multifunctional Au/Hydroxide Interface toward Enhanced C-C Coupling for Solar-Driven CO2 Reduction into C2H6.

The high-grade C2+ products from CO2 photoreduction are limited by the kinetic bottleneck. Herein, a multifunctional Au/hydroxide interface was put forward to improve the C-C coupling. As a prototype, the synthesized Au/ZnSn(OH)6 tuned the CO generation and afforded about 50% electrons toward C2H6 selectivity. The prominent enhancement resulted from the following effects: (1) strong metal-support electronic interactions built an electric field at the interface of ZnSn(OH)6 nearby the Au nanoparticles, leading to fast transfer of electrons for the C-H and C-C bonding reactions. (2) The surface solid-state Sn-OH and Zn-OH lattice hydroxyls served as donors to feed rich H+ and oxygen vacancies (OVs) via hole-induced oxidation for the boosted C2H6 formation. (3) The synergetic OVs and Au sites allowed efficient e-/H+ to boost *CO hydrogenation toward *CH3 and *CH3*CH3 formation into the C2H6 product.

Kinetic Insights into the Tandem and Simultaneous Mechanisms of Propylene Epoxidation by H2 and O2 on Au–Ti Catalysts

Au–Ti proximity is thought to be responsible for propylene epoxidation by H2 and O2 to PO formation (HOPO). However, we find that the Ti sites intimate with Au accounts for small proportion relative to Ti sites remote from Au, based on the semi-quantification of the number of Au nanoparticles and Ti sites on the uncalcined TS-1-supported Au nanoparticle (Au/TS-1-B) catalysts. Whether those remote Ti sites are functioning in PO generation remains unclear. Herein, the abundant remote Ti sites are proposed to catalyze PO formation by the tandem mechanism with the help from the migration of active oxidant species. We isolated the Au sites and Ti sites by physically mixing uncalcined silicalite-1-supported Au (Au/S-1-B) and TS-1-B as a tandem catalyst with much less Au–Ti proximity sites. Comparable performance for HOPO of the mixed catalyst was observed relative to the Au/TS-1-B catalyst, suggesting that the tandem mechanism is also responsible for PO formation. The H2/D2 exchange experiment, in situ diffuse reflectance infrared Fourier transform spectroscopy, and kinetic modeling were combined to further elucidate the mechanism. Only the kinetic model including both the tandem mechanism on remote Ti sites and the simultaneous mechanism on the Au–Ti proximity can well describe the experimental results, and the tandem mechanisms have a larger contribution to PO formation than the simultaneous mechanism on the Au/TS-1-B catalyst with Au nanoparticles on the external surface. However, for the Au/TS-1 catalyst with intraporous tiny Au clusters, the PO formation proceeds by the simultaneous mechanism. This work unveils the function of remote Ti sites in PO formation. Moreover, the kinetic behaviors are connected with the catalyst structure (micropore volume and Au location), which can provide guidance for enhancing the catalytic performance by designing efficient tandem catalysts for the HOPO process.

Transplanting Gold Active Sites into Non-Precious-Metal Nanoclusters for Efficient CO2-to-CO Electroreduction.

Electrocatalytic CO2 reduction reaction (CO2RR) is greatly facilitated by Au surfaces. However, large fractions of underlying Au atoms are generally unused during the catalytic reaction, which limits mass activity. Herein, we report a strategy for preparing efficient electrocatalysts with high mass activities by the atomic-level transplantation of Au active sites into a Ni4 nanocluster (NC). While the Ni4 NC exclusively produces H2, the Au-transplanted NC selectively produces CO over H2. The origin of the contrasting selectivity observed for this NC is investigated by combining operando and theoretical studies, which reveal that while the Ni sites are almost completely blocked by the CO intermediate in both NCs, the Au sites act as active sites for CO2-to-CO electroreduction. The Au-transplanted NC exhibits a remarkable turnover frequency and mass activity for CO production (206 molCO/molNC/s and 25,228 A/gAu, respectively, at an overpotential of 0.32 V) and high durability toward the CO2RR over 25 h.

Sodium-Directed Photon-Induced Assembly Strategy for Preparing Multisite Catalysts with High Atomic Utilization Efficiency.

Integrating different reaction sites offers new prospects to address the difficulties in single-atom catalysis, but the precise regulation of active sites at the atomic level remains challenging. Here, we demonstrate a sodium-directed photon-induced assembly (SPA) strategy for boosting the atomic utilization efficiency of single-atom catalysts (SACs) by constructing multifarious Au sites on TiO2 substrate. Na+ was employed as the crucial cement to direct Au single atoms onto TiO2, while the light-induced electron transfer from excited TiO2 to Au(Na+) ensembles contributed to the self-assembly formation of Au nanoclusters. The synergism between plasmonic near-field and Schottky junction enabled the cascade electron transfer for charge separation, which was further enhanced by oxygen vacancies in TiO2. Our dual-site photocatalysts exhibited a nearly 2 orders of magnitude improvement in the hydrogen evolution activity under simulated solar light, with a striking turnover frequency (TOF) value of 1533 h-1 that exceeded other Au/TiO2-based photocatalysts reported. Our SPA strategy can be easily extended to prepare a wide range of metal-coupled nanostructures with enhanced performance for diverse catalytic reactions. Thus, this study provides a well-defined platform to extend the boundaries of SACs for multisite catalysis through harnessing metal-support interactions.

The nature of stability and adsorption interactions of binary Au-Li clusters with bridge adsorption structures.

Earlier findings have confirmed that CO molecules have propensities to adsorb on low-coordinated gold atoms (top sites) of Au-based clusters, which can be treated by the Blyholder model wherein the σ donation and π-back donation take place. Here, the structural features and stability of (AuLi)n (n = 1-9) clusters were first analyzed using the GA-DFT method. The new adsorption modes, vibration frequencies and electronic interactions for Au-Li clusters with CO were investigated in detail. More excitingly, we found that CO prefers to adsorb on the bridge sites of the Au-Li clusters rather than on the top sites, which are much lower in energies than the top adsorptions, and the C-O stretching frequencies are also red-shifted. AIMD simulations show that the adsorption structures still have good thermal stability at 500 K. The density of states reveals that the electronic structures of Au-Li clusters have excellent stability for the bridge adsorptions of CO molecules. The ETS-NOCV analysis and NPA charges show that the direction of charge flow is from Au-Li clusters → CO. Our study provides an idea to elucidate the new adsorption mechanism on Au-Li clusters and the connection between the geometries and reaction properties.

Oxidation Catalysis of Au Nano-Particles Immobilized on Titanium(IV)- and Alkylthiol-Functionalized SBA-15 Type Mesoporous Silicate Supports

Novel Au nano-particle catalysts immobilized on both titanium(IV)- and alkylthiol-functionalized SBA-15 type ordered mesoporous silicate supports were developed. The bi-functionalized SBA-15 type support could be synthesized by a one-pot method. To the synthesized supports, Au was immobilized by the reaction of the alkylthiol groups on the supports with AuCl4−, following reduction with NaBH4. The immobilized amount and the formed structures and the electronic property of the Au species depended on the loading of alkylthiol. The moderate size (2–3 nm) nano particulate Au sites formed on Ti(0.5)-SBASH(0.5) were negatively charged. The aerobic alcohol oxidation activity of the catalysts depended on the loading of alkylthiol and the structure of the Au nano-particles. The non-thiol-functionalized catalyst (Au/Ti(0.5)-SBASH(0)) composed of the large (5–30 nm) and the higher thiol-loaded catalyst (Au/Ti(0.5)-SBASH(8)) composed of the small cationic Au species were almost inactive. The most active catalyst was Au/Ti(0.5)-SBASH(0.5) composed of the electron-rich Au nano-particles formed by the electron donation from the highly dispersed thiol groups. Styrene oxidation activity in the presence of 1-phenylethanol with O2 depended on the loadings of titanium(IV) on the Au/Ti(x)-SBASH(0.5). The titanium(IV) sites trapped the H2O2 generated through the alcohol oxidation reaction, and also contributed to the alkene oxidation by activating the trapped H2O2.

Bimetallic Au-Ag catalysts in HCHO catalytic oxidation: No synergetic effect?

We prepared AuAg bimetallic catalysts by sequential deposition method to study the role of Au and Ag in the HCHO catalytic oxidation behavior respectively. We found that the highest activity is found for Au monometallic catalyst, rather than AuAg bimetallic catalyst, which is related to the different HCHO oxidation reaction pathways over Au and Ag active sites from in situ DRIFTS results. In this work, different HCHO conversion pathways were found over the Au and Ag active sites, which consume the surficial OH groups and reactive oxygen species on the catalyst surface respectively, denoted as OH-assisted and Oa-assisted pathways. Au active site is dominated by the OH-assisted pathway because of its excellent activation ability to HCHO reaction intermediates. Ag active site is dominated by the Oa-assisted pathway because of its excellent activation ability to oxygen. In this paper, the catalytic behavior of AuAg bimetallic nanoparticles and the different role of Au and Ag active sites in reaction pathways in HCHO oxidation is clarified and discussed for the first time.

Kinetics of Propylene Epoxidation over Extracrystalline Gold Active Sites on AU/TS-1 Catalysts

To determine whether the catalytic roles of extracrystalline and intracrystalline gold nanoparticles supported on titanosilicate-1 (TS-1) for direct propylene epoxidation are intrinsically different, the kinetics of direct propylene epoxidation were measured in a gas-phase continuous stirred tank reactor (CSTR) over polyvinylpyrrolidone-coated (PVP) gold nanoparticles (Au-PVP/TS-1) deposited on TS-1. The as-made PVP-coated gold nanoparticles were too large to fit into the micropores of TS-1, even after ligands were removed in situ by a series of pretreatments, as confirmed by both TEM and TGA-DSC. The activation energy (51 kJ mol–1) and reaction orders for H2 (1.3), O2 (0.4), propylene (0.4), propylene oxide (−0.6), carbon dioxide (0), and water (0) for propylene epoxidation measured on Au-PVP/TS-1 were consistent with those reported for Au/TS-1 prepared via deposition-precipitation (Au-DP/TS-1) (52 kJ mol–1, H2, 1; O2, 0.4; C3H6, 0.4; C3H6O, −0.6; CO2, 0; H2O, 0). However, while the reaction orders for hydrogen oxidation on Au-PVP/TS-1 (H2, 0.8; O2, 0; C3H6, −0.3; C3H6O, −0.1; CO2, 0; H2O, −0.2) were similar to those measured on Au-DP/TS-1 (H2, 0.9; O2, 0.3; C3H6, −0.3; C3H6O, 0; CO2, 0; H2O, −0.1), a decrease in activation energy from approximately 30 kJ mol–1 for Au-DP/TS-1 to 4–5 kJ mol–1 for Au-PVP/TS-1 suggests there is a change in rate-limiting step or active site for hydrogen oxidation. Additionally, an active site model was developed which determines the number of Ti within an interaction range of the perimeter of extracrystalline Au nanoparticles (i.e., the number of Au–Ti active site pairs). This model was used to estimate catalytic turnover frequencies over solely proximal Au–Ti pairs, assuming that hydrogen peroxide does not desorb and migrate from Au sites to Ti sites and instead propylene oxide forms in a concerted mechanism previously termed the “simultaneous” mechanism. Turnover frequencies estimated for this active site model for a data set containing both Au-DP/TS-1 and Au-PVP/TS-1 were ∼20× higher than the highest previous reported estimates (∼80 s–1 vs 1–5 s–1 at 473 K) for catalytic oxidation on noble metals, suggesting that the simultaneous mechanism occurring over proximal Au–Ti sites alone is incapable of explaining the observed rate of propylene epoxidation and that short-range migration of hydrogen peroxide is kinetically relevant. The agreement of reaction orders, activation energy, and active site model for propylene epoxidation on both Au-DP/TS-1 and Au-PVP/TS-1 suggests a common mechanism for propylene epoxidation on both catalysts containing small intraporous gold clusters and catalysts with exclusively larger extracrystalline gold nanoparticles. Rates of hydrogen oxidation were found to vary proportionally to the amount of surface gold atoms. This is also consistent with the hypothesis that the observed decrease in hydrogen efficiency and PO site-time-yield per gold mass with increasing gold loading are driven primarily by the gold dispersion in Au/TS-1 catalysts.

Mechanistic insight the visible light driven hydrogen generation by plasmonic Au-Cu alloy mounted on TiO2 @B-doped g-C3N4 heterojunction photocatalyst

Designing of two dimensional surfaces and interfaces with light-active materials has been established as a versatile approach to increase their photocatalytic activity. In the present work, n-type anatase TiO 2 coupled with p-type B-doped g-C 3 N 4 nanosheet (BCN) were fabricated and Au-Cu nanoalloy with varying atomic ratio were deposited on the p-n heterojunction. The incorporation of Au-Cu on the interface of the dyad enhances light absorption over broad regime, charge separation, and migration. Au-Cu with 1:1 ratio (with an average particle size of 1.2 nm) loaded p-n hetrojunction (TBCAC-1:1) shows excellent photocurrent enhancement (approximately 4.4-folds) in the cathodic direction as compared to their monometallic plasmonic counterpart. Additionally, the catalyst shows photocurrent at zero biased potential as well as lower onset potential as compared to the other alloy. TBCAC-1:1 photocatalyst could able to produce 2150 μmol h −1 g −1 of hydrogen, which is (approximately 3-folds) as compared to their monometallic counterparts. The hydrogen evolution process for Au-Cu (1:1) system was found to be governed by the charge distribution which dictates the binding preference of the Au and Cu sites leading to the water splitting as investigated by DFT calculation. The excellent hydrogen generation by the photocatalyst links to the synergistic effect between Au and Cu associated with the hot electron photochemistry due to surface plasmon resonance phenomenon. Hot electron mediated H 2 generation by a plasmonic TiO 2 /BCN/Au-Cu photocatalyst • n-type TiO 2 with p-type B-doped g-C 3 N 4 nanosheet (BCN) were fabricated and Au-Cu nanoalloy were deposited on it. • Au-Cu on the interface of the dyad enhances light absorption over broad regime, charge separation, and migration. • Au-Cu with 1:1 ratio loaded p-n hetrojunction (TBCAC-1:1) shows excellent photocurrent enhancement in the cathodic direction as compared to other. • TBCAC-1:1 produced 2150 μmol h -1 g -1 of hydrogen (approximately 3-folds) as compared to monometallic counterparts. • The hydrogen evolution process is governed by the charge distribution between Au and Cu sites investigated by DFT calculation.

Highly Efficient Electrocatalytic Upgrade of n-Valeraldehyde to Octane over Au SACs-NiMn2 O4 Spinel Synergetic Composites.

In this work, electrocatalytic upgrade of n-valeraldehyde to octane with higher activity and selectivity is achieved over Au single-atom catalysts (SACs)-NiMn2 O4 spinel synergetic composites. Experiments combined with density functional theory calculation collaboratively demonstrate that Au single-atoms occupy surface Ni2+ vacancies of NiMn2 O4 , which play a dominant role in n-valeraldehyde selective oxidation. A detailed investigation reveals that the initial n-valeraldehyde molecule preferentially adsorbs on the Mn tetrahedral site of NiMn2 O4 spinel synergetic structures, and the subsequent n-valeraldehyde molecule easily adsorbs on the Ni site. Specifically, Au single-atom surficial derivation over spinel lowers the adsorption energy (Eads ) of the initial n-valeraldehyde molecule, which will facilitate its adsorption on the Mn site of Au SACs-NiMn2 O4 . Furthermore, the single-atom Au surficial derivation not only alters the electronic structure of Au SACs-NiMn2 O4 but also lower the Eads of subsequent n-valeraldehyde molecule. Hence, the subsequent n-valeraldehyde molecules prefer adsorption on Au sites rather than Ni sites, and the process of two alkyl radicals originating from Mn-C4 H9 and Au-C4 H9 dimerization into an octane is accordingly accelerated. This work will provide an avenue for the rational design of SACsand supply a vital mechanism for understanding the electrocatalytic upgrade of n-valeraldehyde to octane.

Enhancing catalytic activity of Fe3O4 for electrochemical water oxidation via the coupling of OER-inert Au

Interfacial charge transfer efficiency and electronic states of active sites are two essential issues to restrict catalytic activity of electrocatalysts for oxygen evolution reaction (OER). In this work, we show that although Au is recognized to be inert towards OER, the catalytic activity of Fe3O4 catalyst for OER was highly boosted by coupling Fe3O4 with Au to address these two issues. Here, Au nanoparticles were attached to hierarchical Fe3O4 microsphere through electrochemical deposition, a mild and rapid approach that can be accomplished within 3 min and requires no sophisticated equipment. With the coupling of Au, interfacial charge transfer resistance of Fe3O4 declined remarkably. On the other hand, oxidability of Fe sites and electron accepting capability of Au sites was elevated due to strong interaction between Au and Fe3O4. Owing to these two merits induced by Au, Fe3O4 exhibited enhanced catalytic activity for OER. The potential of Fe3O4 to obtain 10 mA/cm2 decreased by 640 mV, the current density was amplified up to 2.5 fold at the potential of 2 V (vs SCE), and the Tafel slop was reduced by 146 mV/dec.