Geometrically Controlled Nanoporous PdAu Bimetallic Catalysts with Tunable Pd/Au Ratio for Direct Ethanol Fuel Cells

Electrocatalytic Oxidation of Methanol and Ethanol with 3d-Metal Based Anodic Electrocatalysts in Alkaline Media Using Carbon Based Electrode Assembly

Homogeneous electrocatalytic systems based on readily available, earth-abundant, inexpensive base metals Ni, Co, and Cr have been formulated for the electro-oxidation of alcohols (methanol and ethanol) that constitute a key half-cell component of direct alcohol fuel cells (DAFCs). Notably, excellent results were obtained for both methanol as well as ethanol electro-oxidation while operating with a half-cell assembly based on all-non-noble working and counter electrode systems consisting of glassy carbon and graphite rod, respectively. Using NaOH as the supporting electrolyte, Ni/Co/Cr metal salts and their bis(iminopyridine) complexes have been used as anodic electrocatalysts for the alcohol half-cell reactions, and among them, catalytic systems based on Co outperformed the corresponding systems based on Ni and Cr. The system comprising CoCl2.·6H2O [10 mM] + NaOH [6 M] at room temperature emerged as the best electrocatalyst for both methanol [5 M] electro-oxidation (ca. 522.5 ± 13.5 mA cm-2 at 1.4 V) and ethanol [5 M] electro-oxidation (ca. 209 ± 25 mA cm-2 at 1.34 V). It was observed that regardless of the starting alcohol, the end product is carbon dioxide, all of which gets trapped as sodium carbonate (up to 97% yield), thereby mitigating any possible hazards of greenhouse gas emission. Inferences obtained from FETEM, FESEM, and EDS analysis of both the electrolyte solution and residues deposited on the electrode surface provide evidence for the mostly homogeneous nature of the reaction mixture with the molecular catalyst being the major contributor toward the electrocatalytic activity apart from the minor role played by trace heterogeneous particles. The current cell assembly operating with non-noble working and counter electrodes utilizing a catalytic system based on an earth-abundant, base metal salt/complex that not only results in good half-cell current densities for high-energy power-source DAFCs but also generates high-value sodium carbonate offers an exciting avenue.

Stability of Single Gold Atoms on Defective and Doped Diamond Surfaces

Polycrystalline boron-doped diamond (BDD) is widely used as a working electrode material in electrochemistry, and its properties, such as its stability, make it an appealing support material for nanostructures in electrocatalytic applications. Recent experiments have shown that electrodeposition can lead to the creation of stable small nanoclusters and even single gold adatoms on the BDD surfaces. We investigate the adsorption energy and kinetic stability of single gold atoms adsorbed onto an atomistic model of BDD surfaces by using density functional theory. The surface model is constructed using hybrid quantum mechanics/molecular mechanics embedding techniques and is based on an oxygen-terminated diamond (110) surface. We use the hybrid quantum mechanics/molecular mechanics method to assess the ability of different density functional approximations to predict the adsorption structure, energy, and barrier for diffusion on pristine and defective surfaces. We find that surface defects (vacancies and surface dopants) strongly anchor adatoms on vacancy sites. We further investigated the thermal stability of gold adatoms, which reveals high barriers associated with lateral diffusion away from the vacancy site. The result provides an explanation for the high stability of experimentally imaged single gold adatoms on BDD and a starting point to investigate the early stages of nucleation during metal surface deposition.

Nanoporous Gold: From Structure Evolution to Functional Properties in Catalysis and Electrochemistry

Nanoporous gold (NPG) is characterized by a bicontinuous network of nanometer-sized metallic struts and interconnected pores formed spontaneously by oxidative dissolution of the less noble element from gold alloys. The resulting material exhibits decent catalytic activity for low-temperature, aerobic total as well as partial oxidation reactions, the oxidative coupling of methanol to methyl formate being the prototypical example. This review not only provides a critical discussion of ways to tune the morphology and composition of this material and its implication for catalysis and electrocatalysis, but will also exemplarily review the current mechanistic understanding of the partial oxidation of methanol using information from quantum chemical studies, model studies on single-crystal surfaces, gas phase catalysis, aerobic liquid phase oxidation, and electrocatalysis. In this respect, a particular focus will be on mechanistic aspects not well understood, yet. Apart from the mechanistic aspects of catalysis, best practice examples with respect to material preparation and characterization will be discussed. These can improve the reproducibility of the materials property such as the catalytic activity and selectivity as well as the scope of reactions being identified as the main challenges for a broader application of NPG in target-oriented organic synthesis.

Synthesis of Carbon-Supported PdIrNi Catalysts and Their Performance towards Ethanol Electrooxidation

Direct ethanol fuel cells (DEFCs) have shown a high potential to supply energy and contribute to saving the climate due to their bioethanol sustainability and carbon neutrality. Nonetheless, there is a consistent need to develop new catalyst electrodes that are active for the ethanol oxidation reaction (EOR). In this work, two C-supported PdIrNi catalysts, that have been reported only once, are prepared via a facile NaBH₄ co-reduction route. Their physiochemical characterization (X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS)) results show alloyed PdIrNi nanoparticles that are well dispersed (<3 nm) and exist in metallic state that is air-stable apart from Ni and, slightly, Pd. Their electrocatalytic activity towards EOR was evaluated by means of cyclic voltammetry (CV) and chronoamperometry (CA). Even though the physiochemical characterization of PdIrNi/C and Pd₄Ir₂Ni₁/C is promising, their EOR performance has proven them less active than their Pd/C counterpart. Although the oxidation current peak of Pd/C is 1.8 A/mgPd, it is only 0.48 A/mgPd for Pd₄Ir₂Ni₁/C and 0.52 A/mg_Pd for PdIrNi/C. These results were obtained three times and are reproducible, but since they do not add up with the sound PdIrNi microstructure, more advanced and in situ EOR studies are necessary to better understand the poor EOR performance.

Synthesis and Characterization of PdAgNi/C Trimetallic Nanoparticles for Ethanol Electrooxidation

The direct use of ethanol in fuel cells presents unprecedented economic, technical, and environmental opportunities in energy conversion. However, complex challenges need to be resolved. For instance, ethanol oxidation reaction (EOR) requires breaking the rigid C–C bond and results in the generation of poisoning carbonaceous species. Therefore, new designs of the catalyst electrode are necessary. In this work, two trimetallic Pd_xAg_yNi_z/C samples are prepared using a facile borohydride reduction route. The catalysts are characterized by X-ray diffraction (XRD), Energy-Dispersive X-ray spectroscopy (EDX), X-ray photoelectron Spectroscopy (XPS), and Transmission Electron Microscopy (TEM) and evaluated for EOR through cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). The XRD patterns have shown a weak alloying potential between Pd, and Ag prepared through co-reduction technique. The catalysts prepared have generally shown enhanced performance compared to previously reported ones, suggesting that the applied synthesis may be suitable for catalyst mass production. Moreover, the addition of Ag and Ni has improved the Pd physiochemical properties and electrocatalytic performance towards EOR in addition to reducing cell fabrication costs. In addition to containing less Pd, The PdAgNi/C is the higher performing of the two trimetallic samples presenting a 2.7 A/mg_Pd oxidation current peak. The Pd₄Ag₂Ni₁/C is higher performing in terms of its steady-state current density and electrochemical active surface area.

Electrocatalysis of gold-based nanoparticles and nanoclusters

Gold (Au)-based nanomaterials, including nanoparticles (NPs) and nanoclusters (NCs), have shown great potential in many electrocatalytic reactions due to their excellent catalytic ability and selectivity. In recent years, Au-based nanostructured materials have been considered as one of the most promising non-platinum (Pt) electrocatalysts. The controlled synthesis of Au-based NPs and NCs and the delicate microstructure adjustment play a vital role in regulating their catalytic activity toward various reactions. This review focuses on the latest progress in the synthesis of efficient Au-based NP and NC electrocatalysts, highlighting the relationship between Au nanostructures and their catalytic activity. This review first discusses the parameters of Au-based nanomaterials that determine their electrocatalytic performance, including composition, particle size and architecture. Subsequently, the latest electrocatalytic applications of Au-based NPs and NCs in various reactions are provided. Finally, some challenges and opportunities are highlighted, which will guide the rational design of Au-based NPs and NCs as promising electrocatalysts.

Carbon-Supported Trimetallic Catalysts (PdAuNi/C) for Borohydride Oxidation Reaction

The synthesis of palladium-based trimetallic catalysts via a facile and scalable synthesis procedure was shown to yield highly promising materials for borohydride-based fuel cells, which are attractive for use in compact environments. This, thereby, provides a route to more environmentally friendly energy storage and generation systems. Carbon-supported trimetallic catalysts were herein prepared by three different routes: using a NaBH₄-ethylene glycol complex (PdAuNi/C_SBEG), a NaBH₄-2-propanol complex (PdAuNi/C_SBIPA), and a three-step route (PdAuNi/C_3-step). Notably, PdAuNi/C_SBIPA yielded highly dispersed trimetallic alloy particles, as determined by XRD, EDX, ICP-OES, XPS, and TEM. The activity of the catalysts for borohydride oxidation reaction was assessed by cyclic voltammetry and RDE-based procedures, with results referenced to a Pd/C catalyst. A number of exchanged electrons close to eight was obtained for PdAuNi/C_3-step and PdAuNi/C_SBIPA (7.4 and 7.1, respectively), while the others, PdAuNi/C_SBEG and Pd/C_SBIPA, presented lower values, 2.8 and 1.2, respectively. A direct borohydride-peroxide fuel cell employing PdAuNi/C_SBIPA catalyst in the anode attained a power density of 47.5 mW cm⁻² at room temperature, while the elevation of temperature to 75 °C led to an approximately four-fold increase in power density to 175 mW cm⁻². Trimetallic catalysts prepared via this synthesis route have significant potential for future development.

A comprehensive and critical review of the recent progress in electrocatalysts for the ethanol oxidation reaction

The human craving for energy is continually mounting and becoming progressively difficult to gratify. At present, the world's massive energy demands are chiefly encountered by nonrenewable and benign fossil fuels. However, the development of dynamic energy cradles for a gradually thriving world to lessen fossil fuel reserve depletion and environmental concerns is currently a persistent issue for society. The discovery of copious nonconventional resources to fill the gap between energy requirements and supply is the extreme obligation of the modern era. A new emergent, clean, and robust alternative to fossil fuels is the fuel cell. Among the different types of fuel cells, the direct ethanol fuel cell (DEFCs) is an outstanding option for light-duty vehicles and portable devices. A critical tactic for obtaining sustainable energy sources is the production of highly proficient, economical and green catalysts for energy storage and conversion devices. To date, a broad range of research is available for using Pt and modified Pt-based electrocatalysts to augment the C₂H₅OH oxidation process. Pt-based nanocubes, nanorods, nanoflowers, and the hybrids of Pt with metal oxides such as Fe₂O₃, TiO₂, SnO₂, MnO, Cu₂O, and ZnO, and with conducting polymers are extensively utilized in both acidic and basic media. Moreover, Pd-based materials, transition metal-based materials, as well as transition metal-based materials are also points of interest for researchers nowadays. This review article delivers a broad vision of the current progress of the EOR process concerning noble metals and transition metals-based materials.

Insight into the electrocatalytic performance of in-situ fabricated electroactive biofilm-Pd: The role of biofilm thickness, initial Pd(II) concentration and the exposure time to Pd precursor

Biogenic palladium (bio-Pd) nanoparticles have been considered as promising biocatalyst for energy generation and contaminants remediation in water and sediment. Recently, an electroactive biofilm-Pd (EAB-Pd) network, which can be used directly as electrocatalyst and show enhanced electrocatalytic performance, has exhibited tremendous application potential. However, the information regarding to the controllable biosynthetic process and corresponding catalytic properties is scarce. This study demonstrated that the catalytic performance of EAB-Pd could be influenced by Pd loading on bacteria cells (Pd/cells), which was crucial to determine the final distribution characteristic of Pd nanocrystal on EAB skeleton. For instance, the high Pd/cells (over 0.18 pg cell^-1) exhibited almost 6-fold and 1.5-fold enhancement over EAB-Pds with Pd/cells below 0.03 in catalytic current toward hydrogen evolution reaction and nitrobenzene reduction, respectively. In addition, the Pd/cells was found to be affected by the synthesis factors, such as the ratio of biomass to initial Pd(II) concentration (cells/Pd_II) and the exposure time of EAB to Pd(II) precursor solution. The Pd/cells increased significantly as the cell/Pd_II ratio decreased from ~5.5 × 10⁷ to ~1.3 × 10⁷ cells L mg^-1 or the prolongation of exposure time from 3 h to 24 h. The findings developed in this work extensively expand our knowledge for the in-situ designing biogenic electrocatalyst and provide important information for the development of its catalytic property.

Promoting Effects of Au Submonolayer Shells on Structure-Designed Cu-Pd/Ir Nanospheres: Greatly Enhanced Activity and Durability for Alkaline Ethanol Electro-Oxidation

Rationally engineering the surface physicochemical properties of nanomaterials can improve their activity and durability for various electrocatalytic and energy conversion applications. Cu-Pd/Ir (CPI) nanospheres (NSs) anchored on N-doped porous graphene (NPG) [(CPI NSs/NPG)] have been recently demonstrated as a promising electrocatalyst for the alkaline ethanol oxidation reaction (EOR); to further enhance their electrocatalytic performance, the NPG-supported CPI NSs are coated with Au submonolayer (SML) shells (SMSs), through which their surface physicochemical properties can be tuned. CPI NSs/NPG is prepared by our previously developed method and possesses the special structures of composition-graded Cu₁Pd₁ and surface-doped Ir_0.03. The Au SMSs with designed surface coverages are formed via an electrochemical technology involving incomplete Cu underpotential deposition (UPD) and Au³⁺ galvanic replacement. A distinctive volcano-type relation between the EOR electrocatalytic activity and the Au-SMS surface coverage for CPI@Au_SML NSs/NPG is revealed, and the optimal CPI@Au_1/6ML NSs/NPG greatly surpasses commercial Pd/C and CPI NSs/NPG in electrocatalytic activity and noble metal utilization. More importantly, its electrocatalytic durability in 1 h chronoamperometric and 500-cycle potential cycling degradation tests is also significantly improved. According to detailed physicochemical characterizations, electrochemical analyses, and density functional theory calculations, the promoting effects of the Au SMS for enhancing the EOR electrocatalytic activity and durability of CPI NSs/NPG can be mainly attributed to the greatly weakened carbonaceous intermediate bonding and properly increased surface oxidation potential. This work also proposes a versatile and effective strategy to tune the surface physicochemical properties of metal-based nanomaterials via incomplete UPD and metal-cation galvanic replacement for advancing their electrocatalytic and energy conversion performance.

Manipulation of Neighboring Palladium and Mercury Atoms for Efficient *OH Transformation in Anodic Alcohol Oxidation and Cathodic Oxygen Reduction Reactions

The synergetic effect of neighboring heterogeneous atoms is capable of enabling unexpected catalytic performance, and the design of a well-ordered atomic structure and elaborating the underlying interactions are crucial for the development of superior electrocatalysts in fuel cells. We demonstrate here that an ordered Pd-Hg intermetallic alloy with dimensions of several nanometers can be subtly manipulated using a mild wet-chemical reduction approach. On the basis of combined results of XPS and HAADF-STEM analysis, the adjacent regions of metallic atoms were found to be evenly occupied by heterogeneous elements from the distribution features of the surface structure. Due to charge transfer from Hg to neighboring Pd, the down-shift of the d-band center in PdHg alloys was theoretically beneficial for desorption of crucial intermediates (*OH), both in anodic ethanol oxidation reaction (EOR) and in cathodic oxygen reduction reaction (ORR). In the presence of Hg atoms with lower *OH desorption energy, the rapid dissociation of *OH from Pd facilitated the final H₂O formation, with superior ORR efficiency comparable to Pt/C catalysts. Remarkably, the rapid combination of *OH on Hg atoms with CH₃CO* on neighboring Pd atoms unambiguously favored generation of acetate ions (rate-determining) in the catalytic EOR process, resulting in a high mass activity (7.68 A per mgPd). This well-ordered atomic structure also shows excellent long-term stability in ethylene glycol oxidation reaction and ORR.

Bimetallic alloy and semiconductor support synergistic interaction effects for superior electrochemical catalysis

The design and fabrication of economically viable anode catalysts for the methanol oxidation reaction (MOR) have been challenging issues in direct methanol fuel cells (DMFCs) over the decades. In this work, a composite electrochemical catalyst of Pd-coupled Ag and ZnO for the possible replacement of expensive Pt catalysts in DMFCs is successfully prepared. The as-made Pd@Ag/ZnO exhibits specific activity, which is 1.8-fold, 2.8-fold, and 4.6-fold higher than that of a Pd/ZnO catalyst, 20% Pd/C catalyst and Pd black, respectively. The improvement of the catalytic mechanism is likely due to the synergistic interaction between Pd@Ag and ZnO. The density functional theory (DFT) calculation results confirm that Ag doped into Pd weakens the adsorption of CO, dramatically improving the capability to resist CO poisoning.

One Step Synthesis of a Gold/Ordered Mesoporous Carbon Composite Using a Hard Template Method for Electrocatalytic Oxidation of Methanol and Colorimetric Determination of Glutathione

Ordered mesoporous carbon-supported gold nanoparticles (Au/OMC) have been fabricated in one step through a hard template method using gold nanoparticle-intercalated mesoporous silica (GMS) to explore two different catalytic properties, for example, electrocatalytic oxidation of methanol and colorimetric determination of glutathione (GSH). The catalytically inert but conducting nature of mesoporous carbon (OMC) and promising catalytic activity of gold nanoparticles (AuNPs) has inspired us to synthesize Au/OMC. The as-prepared Au/OMC catalyst was characterized by powder X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray analysis-elemental mapping, and X-ray photoelectron spectroscopy. The characterization results indicate that AuNPs are uniformly distributed on the surface of OMC. The conducting-OMC framework with a high surface area of Au/OMC provides superior transport of electrons through the porous surface of carbon matrix and resulted in its high efficiency and stability as an electrocatalyst for the oxidation of methanol in comparison to CMK-3, SBA-15, and GMS in alkaline medium. The efficiency of Au/OMC toward methanol oxidation in alkaline medium is much higher in comparison to that in acidic medium. The lower value of I f/I b in the acidic medium in comparison to that in the alkaline medium clearly indicates that the oxidation process with Au/OMC as a catalyst is much more superior in alkaline medium with better tolerance toward the accumulation of intermediate CO species on the active surface area. Furthermore, the Au/OMC catalyst is successfully utilized for the detection and quantification of GSH spectrophotometrically with a limit of detection value of 0.604 nM.

Synthesis and characterization of size controlled bimetallic nanosponges

Metallic and bimetallic nanosponges with well-defined size and form have attracted increasing attention due to their unique structural properties and their potential for many applications. In this chapter, the recently developed methods for the synthesis and preparation of metallic and bimetallic nanosponges are presented. These methods can be mainly cataloged in two groups: dealloying-based methods and reduction reaction-based methods. Different topographical reconstruction methods for the investigation of their structural properties are then reviewed briefly. The optical properties of the metallic nanosponges are clearly different from those of the solid counterparts due to the tailored disordered structure. The recent advances in the exploration of the distinct linear and non-linear optical properties of the nanosponges are summarized.

Graphical Abstract:

Electrochemical tuning of Pd100−xAux bimetallics towards ethanol oxidation: effect of an induced d-band center shift and oxophilicity

Electronegative Au improves the oxidation kinetics of Pd by inducing a downshift of the d-band center and increasing the coverage of adsorbed hydroxyls.

pH-Dependent growth of atomic Pd layers on trisoctahedral gold nanoparticles to realize enhanced performance in electrocatalysis and chemical catalysis

In this work, the controlled epitaxial growth of ultrathin Pd shells of a few atomic layers (denoted as nL) on the surfaces of gold nanoparticle (Au NP) cores of different morphologies (trisoctahedral, cubic, and spherical shapes) in the presence of cetyltrimethylammonium chloride (CTAC) was achieved by regulating the pH value of the aqueous CTAC solution and finely tuning the amount of the Pd precursor. It was found that the critical shell thickness for epitaxial Pd growth at the optimal pH value was 4 atomic layers, taking {331}-faceted trisoctahedral (TOH) Au@Pd_nL NPs as an example, on the basis of the results of atomic-resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images. Moreover, the resulting TOH Au@Pd_1L NPs (100.9 m² g^-1, 13.2 A mg_Pd^-1 and 13.1 mA cm^-2) exhibited excellent electrocatalytic performance and long-term electrocatalytic activity for ethanol oxidation, around 4.8-fold, 66-fold, and 21.8-fold better than commercial Pd/C catalysts (31 m² g^-1, 0.2 A mg_Pd^-1, and 0.6 mA cm^-2). Furthermore, the resulting TOH Au@Pd_1L NPs not only markedly enhance the chemical catalytic activity for the reduction of 4-nitrophenol (4-NP), but also allow the in situ surface-enhanced Raman spectroscopy (SERS) monitoring of the reaction process of the Pd-catalyzed reduction of 4-NTP. Thus, our work may provide a new way to fabricate core-shell (CS) bimetallic NPs with the merits of both metal outer shells (excellent catalytic performance in electrocatalysis and chemical catalysis) and Au NP cores (reaction process by in situ SERS monitoring).

Amperometric nonenzymatic sensing of glucose at very low working potential by using a nanoporous PdAuNi ternary alloy

The authors present a nonenzymatic sensor for glucose that has an exceedingly low working potential which makes the sensor highly selective over other electroactive species. The sensor is based on the use of a glassy carbon electrode (GCE) that was modified with a nanoporous PdAuNi alloy (np-PdAuNi). The PdAuNi alloy nanostructure displays enhanced electrocatalytic activity for glucose oxidation (compared to PdNi alloys). The modified GCE enables amperometric sensing of glucose at a typical working electrode potential of 0.0 V vs. SCE in solutions of pH 13 containing 0.1 M NaCl. Response is linear in the 5 to 100 μM concentration range, with a 1.7 μM detection limit (at an S/N ratio of 3). For higher concentrations deviations from linearity were found. The method is selective and reproducible. The modified electrode was applied to the determination of glucose in human serum. Graphical Abstract Nanoporous PdAuNi alloy with three-dimensional bicontinuous nanosponge architecture was successfully prepared via chemical dealloying. The electrochemical nonenzymatic glucose sensor shows a low working potential, wide linear range, good sensitivity, low detection limit and excellent selectivity.

Highly Active Multimetallic Palladium Nanoalloys Embedded in Conducting Polymer as Anode Catalyst for Electrooxidation of Ethanol

Fabrication of multimetallic nanocatalysts with controllable composition remains a challenge for the development of low-cost electrocatalysts, and incorporating metal-based catalysts into active carbon nanoarchitectures represents an emerging strategy to improve the catalytic performance of electrocatalysts. Herein, a facile method developed for Pd nanoparticle (NP)-based multimetallic alloys incorporated on polypyrrole (Ppy) nanofibers by in situ nucleation and growth of NPs using colloidal radiolytic technique is described. Electrochemical measurement suggests that the as-prepared catalysts demonstrate dramatically enhanced electrocatalytic activity for ethanol oxidation in alkaline medium. The ultrasmall Pd₃₀Pt₂₉Au₄₁/Ppy nanohybrids (∼8 nm) exhibit excellent electrocatalytic activity, which is ∼5.5 times higher than that of its monometallic counterparts (12 A/mg Pd, 5 times higher activity compared to that of Pd/C catalyst). Most importantly, the ternary nanocatalyst shows no obvious change in chemical structure and long-term stability, reflected in the 2% loss in forward current density during 1000 cycles. The superior catalytic activity and durability of the nanohybrids have been achieved due to the formation of Pt-Pd-Au heterojunctions with cooperative action of the three metals in the alloy composition, and the strong interactions between the Ppy nanofiber support with the metal NPs. The facile synthetic approach provides a new generation of polymer-supported metal alloy hybrid nanostructures as potential electrocatalysts with superior catalytic activity for fuel cell applications.

Atomic-Level-Designed Catalytically Active Palladium Atoms on Ultrathin Gold Nanowires

A Ag monolayer facilitates the deposition of isolated Pd atoms rather than continuous ones on ultrathin Au nanowires. During the hydrogenation of nitrophenol and the electrooxidation of ethanol, these two groups of Pd atoms show distinctive but geometry-dependent catalytic activity. This new atomic geometry maneuvering strategy is ready for the atomically precise design of nanocatalysts.

Core–shell and alloy integrating PdAu bimetallic nanoplates on reduced graphene oxide for efficient and stable hydrogen evolution catalysts

PdAu nanoplates with different core–shell structures on rGO were generated by manipulating the competition between galvanic replacement and chemical reduction with the alloy and core–shell integrating nanoplates exhibiting superior HER properties.

Catalytic Intervention of MoO3 toward Ethanol Oxidation on PtPd Nanoparticles Decorated MoO3-Polypyrrole Composite Support

Ethanol oxidation reaction has been studied in acidic environment over PtPd nanoparticles (NPs) grown on the molybdenum oxide-polypyrrole composite (MOPC) support. The attempt was focused on using reduced Pt loading on non-carbon support for direct ethanol fuel cell (DEFC) operated with proton exchange membrane (PEM). As revealed in SEM study, a molybdenum oxide network exists in polypyrrole caging and the presence of metal NPs over the composite matrix is confirmed by TEM analysis. Further physicochemical characterizations such as XRD, EDAX, and XPS are followed in order to understand the surface morphology and composition of the hybrid structure. Electrochemical techniques such as voltammetry, choroamperometry, and impedance spectroscopy along with performance testing of an in-house-fabricated fuel cell are carried out to evaluate the catalytic activity of the materials for DEFC. The reaction products are estimated by ion chromatographic analysis. Considering the results obtained from the above characterization procedures, the best catalytic performance is exhibited by the Pt-Pd (1:1) on MOPC support. A clear intervention of the molybdenum oxide network is strongly advocated in the EOR sequence which increases the propensity of the reaction by making the metallites more energy efficient in terms of harnessing sufficient numbers of electrons than with the carbon support.

Microbial synthesis of highly dispersed PdAu alloy for enhanced electrocatalysis

Biosynthesis based on the reducing capacity of electrochemically active bacteria is frequently used in the reduction of metal ions into nanoparticles as an eco-friendly way to recycle metal resources. However, those bionanoparticles cannot be used directly as electrocatalysts because of the poor conductivity of cell substrates. This problem was solved by a hydrothermal reaction, which also contributes to the heteroatom doping and alloying between Pd and Au. With the protection of graphene, the aggregation of nanoparticles was successfully avoided, and the porous structure was maintained, resulting in better electrocatalytic activity and durability than commercial Pd/C under both alkaline (CH₃CH₂OH, 6.15-fold of mass activity) and acidic (HCOOH, 6.58-fold of mass activity) conditions. The strategy developed in this work opens up a horizon into designing electrocatalysts through fully utilizing the abundant resources in nature.