Twisted palladium-copper nanochains toward efficient electrocatalytic oxidation of formic acid

Ultra-Large Two-Dimensional Metal Nanowire Networks by Microfluidic Laminar Flow Synthesis for Formic Acid Electrooxidation

Despite the great research interest in two-dimensional metal nanowire networks (2D MNWNs) due to their large specific surface area and abundance of unsaturated coordination atoms, their controllable synthesis still remains a significant challenge. Herein, a microfluidics laminar flow-based approach is developed, enabling the facile preparation of large-scale 2D structures with diverse alloy compositions, such as PtBi, AuBi, PdBi, PtPdBi, and PtAuCu alloys. Remarkably, these 2D MNWNs can reach sizes up to submillimeter scale (~220 μm), which is significantly larger than the evolution from the 1D or 3D counterparts that typically measure only tens of nanometers. The PdBi 2D MNWNs affords the highest specific activity for formic acid (2669.1 mA mg-1) among current unsupported catalysts, which is 103.5 times higher than Pt-black, respectively. Furthermore, in situ Fourier transform infrared (FTIR) experiments provide comprehensive evidence that PdBi 2D MNWNs catalysts can effectively prevent CO* poisoning, resulting in exceptional activity and stability for the oxidation of formic acid.

Fabrication of heterogeneous bimetallic nanochains through photochemical welding for promoting the electrocatalytic hydrogen evolution reaction

Heterogeneous bimetallic nanochains (NCs) have gained significant attention in the field of catalysis due to their abundant active sites, multi-component synergistic catalytic, and exotic electronic structures. Here, we present a novel approach to synthesize one-dimensional heterogeneous bimetallic nanochains using a local surface plasmon resonance (LSPR) based strategy of liquid-phase photochemical welding method containing self-assembly and subsequent welding processes. Initially, we introduce additives that facilitate the self-assembly and alignment of Au nanoparticles (NPs) into orderly lines. Subsequently, the LSPR effect of the Au NPs is stimulated by light, enabling the second metal precursor to overcome the energy barrier and undergo photodeposition in the gap between the arranged Au NPs, thereby connecting the nano-metal particles. This strategy can be extended to the photochemical welding of Au NPs-Ag and Au NRs. Using electrocatalytic hydrogen evolution reaction (HER) as a proof-of-concept application, the obtained one-dimensional structure of Au5Pt1 NCs exhibit promoted HER performances, where the mass activity of the Au5Pt1 nanochains is found to be 4.8 times higher than that of Au5Pt1 NPs and 10.4 times higher than that of commercial 20 wt% Pt/C catalysts. The promoted HER performance is benefited from the electron conduction ability and abundant active sites.

Bimetallic Nanoalloy Catalysts for Green Energy Production: Advances in Synthesis Routes and Characterization Techniques

Bimetallic Nanoalloy catalysts have diverse uses in clean energy, sensing, catalysis, biomedicine, and energy storage, with some supported and unsupported catalysts. Conventional synthetic methods for producing bimetallic alloy nanoparticles often produce unalloyed and bulky particles that do not exhibit desired characteristics. Alloys, when prepared with advanced nanoscale methods, give higher surface area, activity, and selectivity than individual metals due to changes in their electronic properties and reduced size. This review demonstrates the synthesis methods and principles to produce and characterize highly dispersed, well-alloyed bimetallic nanoalloy particles in relatively simple, effective, and generalized approaches and the overall existence of conventional synthetic methods with modifications to prepare bimetallic alloy catalysts. The basic concepts and mechanistic understanding are represented with purposely selected examples. Herein, the enthralling properties with widespread applications of nanoalloy catalysts in heterogeneous catalysis are also presented, especially for Hydrogen Evolution Reaction (HER), Oxidation Reduction Reaction (ORR), Oxygen Evolution Reaction (OER), and alcohol oxidation with a particular focus on Pt and Pd-based bimetallic nanoalloys and their numerous fields of applications. The high entropy alloy is described as a complicated subject with an emphasis on laser-based green synthesis of nanoparticles and, in conclusion, the forecasts and contemporary challenges for the controlled synthesis of nanoalloys are addressed.

Pronounced effect of yttrium oxide on the activity of Pd/rGO electrocatalyst for formic acid oxidation reaction

A highly efficient and stable electrocatalyst comprised of yttrium oxide (Y₂O₃) and palladium nanoparticles has been synthesized via a sodium borohydride reduction approach. The molar ratio of Pd and Y was varied to fabricate various electrocatalysts and the oxidation reaction of formic acid was checked. X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and X-ray powder diffraction (XRD) are used to characterize the synthesized catalysts. Among the synthesized catalysts (Pd_yY_x/rGO), the optimized catalyst i.e., Pd₆Y₄/rGO exhibits the highest current density (106 mA cm^-2) and lowest onset potential compared to Pd/rGO (28.1 mA cm^-2) and benchmark Pd/C (21.7 mA cm^-2). The addition of Y₂O₃ to the rGO surface results in electrochemically active sites due to the improved geometric structure and bifunctional components. The electrochemically active surface area 119.4 m² g^-1 is calculated for Pd₆Y₄/rGO, which is ∼1.108, ∼1.24, ∼1.47 and 1.55 times larger than Pd₄Y₆/rGO, Pd₂Y₈/rGO, Pd/C and Pd/rGO, respectively. The redesigned Pd structures on Y₂O₃-promoted rGO give exceptional stability and enhanced resistance to CO poisoning. The outstanding electrocatalytic performance of the Pd₆Y₄/rGO electrocatalyst is ascribed to uniform dispersion of small size palladium nanoparticles which is possibly due to the presence of yttrium oxide.

A "Special" Solvent to Prepare Alloyed Pd2Ni1 Nanoclusters on a MWCNT Catalyst for Enhanced Electrocatalytic Oxidation of Formic Acid

Herein, an electrocatalyst with Pd₂Ni₁ nanoclusters, supporting multiwalled carbon nanotubes (MWCNTs) (referred to Pd₂Ni₁/CNTs), was fabricated with deep eutectic solvents (DES), which simultaneously served as reducing agent, dispersant, and solvent. The mass activity of the catalyst for formic acid oxidation reaction (FAOR) was increased nearly four times compared to a Pd/C catalyst. The excellent catalytic activity of Pd₂Ni₁/CNTs was ascribed to the special nanocluster structure and appropriate Ni doping, which changed the electron configuration of Pd to reduce the d-band and to produce a Pd-Ni bond as a new active sites. These newly added Ni sites obtained more OH^- to release more effective active sites by interacting with the intermediate produced in the first step of FAOR. Hence, this study provides a new method for preparing a Pd-Ni catalyst with high catalytic performance.

Pd3Co1 Alloy Nanocluster on the MWCNT Catalyst for Efficient Formic Acid Electro-Oxidation

In this study, the Pd₃Co₁ alloy nanocluster from a multiwalled carbon nanotube (MWCTN) catalyst was fabricated in deep eutectic solvents (DESs) (referred to Pd₃Co₁/CNTs). The catalyst shows a better mass activity towards the formic acid oxidation reaction (FAOR) (2410.1 mA mg_Pd^-1), a better anti-CO toxicity (0.36 V) than Pd/CNTs and commercial Pd/C. The improved performance of Pd₃Co₁/CNTs is attributed to appropriate Co doping, which changed the electronic state around the Pd atom, lowered the d-band of Pd, formed a new Pd-Co bond act at the active sites, affected the adsorption of the toxic intermediates and weakened the dissolution of Pd; moreover, with the assistance of DES, the obtained ultrafine Pd₃Co₁ nanoalloy exposes more active sites to enhance the dehydrogenation process of the FAOR. The study shows a new way to construct a high-performance Pd-alloy catalyst for the direct formic acid fuel cell.

Controllable Synthesis of Web-Footed PdCu Nanosheets and Their Electrocatalytic Applications

Morphological control of noble-metal-based nanocrystals has attracted enormous attention because their catalytic behaviors can be optimized well by adjusting the size and shape. Herein, the controllable synthesis of web-footed PdCu nanosheets via a facile surfactant-free method is reported. It is discovered that the Cu(II) precursor in this synthetic system displays a critical role in growing branches along the lateral of nanosheets. This work demonstrates a Pd-based alloy nanoarchitecture for efficient and stable electrocatalysis of both ethanal and formic acid oxidation reactions.

Localized surface plasmon resonance induced assembly of bimetal nanochains

Bimetal nanochains (NCs) are attracting increasing attention in the fields of catalysis and electrocatalysis due to the synergistic effects in electronic and optical properties, but the fabrication of bimetal NCs remains challenging. Here, we report a general strategy named "nucleation in the irradiation then growth in the dark" for the preparation of Au/M (second metal) NCs. In the irradiation stage, the localized surface plasmon resonance (LSPR) effect of Au NPs is excited to overcome the nucleation energy barrier for the deposition of second metals (Pt, Ag and Pd). In the followed dark process, the preferential growth of second metals on the existed nucleus leads to the formation of nanochain rather than the core/shell nanostructure. In the model reaction of electrocatalytic hydrogen evolution, the optimized Au/Pt NCs showed much better performance compared with the commercial Pt/C.

Bidirectional controlling synthesis of branched PdCu nanoalloys for efficient and robust formic acid oxidation electrocatalysis

Through a two-way control of hexadecyl trimethyl ammonium bromide (CTAB) and hydrochloric acid (HCl), the PdCu nanoalloys with branched structures are synthesized in one step by hydrothermal reduction and used as electrocatalysts for formic acid oxidation reaction (FAOR). In this two-way control strategy, the CTAB is used as a structure-oriented surfactant, while a certain amount of HCl is used to control the reaction kinetics for achieving gradual growth of multi-dendritic structures. The characterizations including scanning transmission electron microscope (STEM), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) suggest that PdCu nanoalloys with unique multi-dendritic branches have favorable electronic structure and lattice strain for electrocatalyzing the oxidation of formic acid. In specific, among the electrocatalysts with different Pd/Cu ratios, the Pd₁Cu₁ branched nanoalloys have the largest electrochemically active surface area (ECSA) and the best performance for the FAOR. The catalytic activity of the Pd₁Cu₁ branched nanoalloys is 2.4 times that of commercial Pd black. After the chronoamperometry test, the Pd₁Cu₁ branched nanoalloys still maintain their original morphologies and higher current density than that of the commercial Pd black. In addition, in the CO-stripping tests, the initial oxidation potential and the oxidation peak potential of the PdCu branched nanoalloys for CO adsorption are lower than those of commercial Pd balck, evincing their better anti-poisoning performance.

General Synthesis of Amorphous PdM (M = Cu, Fe, Co, Ni) Alloy Nanowires for Boosting HCOOH Dehydrogenation

Noble metal-based nanomaterials with amorphous structures are promising candidates for developing efficient electrocatalysts. However, their synthesis remains a significant challenge, especially under mild conditions. In this paper, we report a general strategy for preparing amorphous PdM nanowires (a-PdM NWs, M = Fe, Co, Ni, and Cu) at low temperatures by exploiting glassy non-noble metal (M) nuclei generated by special ligand adsorption as the amorphization dictator. When evaluated as electrocatalysts toward formic acid oxidation, a-PdCu NWs can deliver the mass and specific activities as high as 2.93 A/mg_Pd and 5.33 mA/cm², respectively; these are the highest values for PdCu-based catalysts reported thus far, far surpassing the crystalline-dominant counterparts and commercial Pd/C. Theoretical calculations suggest that the outstanding catalytic performance of a-PdCu NWs arises from the amorphization-induced high surface reactivity, which can efficiently activate the chemically stable C-H bond and thereby significantly facilitate the dissociation of HCOOH.

Boosting the electrocatalytic activity of Pd/C by Cu alloying: Insight on Pd/Cu composition and reaction pathway

Tuning composition of Pd-based bimetallic electrocatalysts of high stability and durability is of great importance in energy-related reactions. This study reports the remarkable electrocatalytic performance of carbon-supported bimetallic Pd-Cu alloy nanoparticles (NPs) towards formic acid oxidation (FAO) and oxygen reduction reaction (ORR). Among various bimetallic compositions, Pd₃Cu/C alloy NPs exhibits the best FAO and ORR activity. During FAO reaction, Pd₃Cu/C alloy NPs exhibits a peak with a current density of 28.33 mA cm^-2 and a potential of 0.2 V (vs. Ag/AgCl) which is higher than that of the other PdCu compositions and standard 20 wt% Pd/C catalyst. Meanwhile, the onset potential (-0.09 V), half-wave potential (-0.18 V), limiting current density at 1600 rpm (-4.9 mA cm^-2) and Tafel slope (64 mV dec^-1) values of Pd₃Cu/C alloy NPs validate its superiority over the conventional 20 wt% Pt/C catalyst for ORR. Experimental and DFT studies have confirmed that the enhanced activity can be attributed to the electronic effect that arises after Cu alloying which causes a downshift of Pd d-band center and structural effect that produces highly dispersed NPs over the carbon matrix with high electrochemically active surface area.

Hierarchical defective palladium-silver alloy nanosheets for ethanol electrooxidation

Tuning the chemical composition and surface structure of electrodes is demonstrated as a feasible and effective strategy to tailor advanced catalysts for energy electrocatalysis. In this work, hierarchical palladium-silver alloy nanosheets (PdAg NS) with the thickness ~7 atoms and rich atomic defects are successfully prepared, using the carbon monoxide (CO) confinement approach. The optimized Pd₇Ag₃ NS/C exhibits 8.8 times higher catalytic peak current density and much better stability toward ethanol electrooxidation than Pd NS/C catalyst. The catalytic enhancement mechanism could be attributed to the synergetic effects among optimized electronic structure of Pd, novel architecture, and rich atomic defects.

Anomalous detwinning in constrained Cu nanoparticles

In this work, the detwinning process in a 9 nm graphene-constrained Cu nanoparticle was investigated at 1009 °C via in situ high-resolution transmission electron microscopy. Instead of the expected reverse glide of the twinning dislocations, two new twins were formed; the four twin zones rotated synergistically before vanishing. Furthermore, the twin boundary migration energy and the system energy were increased continuously with detwinning. The increased resistance to twin boundary migration in constrained nanoparticles enriches our understanding of the twinning mechanism and may facilitate the design of high-strength and high-ductility nanomaterials.

High Active PdSn Binary Alloyed Catalysts Supported on B and N Codoped Graphene for Formic Acid Electro-Oxidation

A series of PdSn binary catalysts with varied molar ratios of Pd to Sn are synthesized on B and N dual-doped graphene supporting materials. The catalysts are characterized by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). Formic acid electro-oxidation reaction is performed on these catalysts, and the results reveal that the optimal proportion of Pd:Sn is 3:1. X-ray photoelectron spectroscopy (XPS) measurements show that when compared with 3Pd1Sn/graphene, B and N co-doping into the graphene sheet can tune the electronic structure of graphene, favoring the formation of small-sized metallic nanoparticles with good dispersion. On the other hand, when compared with the monometallic counterparts, the incorporation of Sn can generate oxygenated species that help to remove the intermediates, exposing more active Pd sites. Moreover, the electrochemical tests illustrate that 3Pd1Sn/BN-G catalyst with a moderate amount of Sn exhibits the best catalytic activity and stability on formic acid electro-oxidation, owing to the synergistic effect of the Sn doping and the B, N co-doping graphene substrate.

CO-Reductive and O2-Oxidative Annealing Assisted Surface Restructure and Corresponding Formic Acid Oxidation Performance of PdPt and PdRuPt Nanocatalysts

Formic acid oxidation reaction (FAOR) at anode counterpart incurs at substantial high overpotential, limiting the power output efficiency of direct formic acid fuel cells (DFAFCs). Despite intense research, the lack of high-performance nanocatalysts (NCs) for FAOR remains a challenge in realizing DFAFC technologies. To surmount the overpotential losses, it is desirable to have NCs to trigger the FAOR as close to the reversible conditions (i.e. with over-potential loss as close to zero as possible). Herein, Pd-based binary and ternary NCs consisting of PdPt and PdRuPt have been synthesized via the polyol reduction method on the carbon support. As prepared PdPt and PdRuPt NCs were further subjected to heat treatment (annealed) in CO (namely PdPt-CO and PdRuPt-CO) and O2 (namely PdPt-O2 and PdRuPt-O2) atmosphere at 473 K temperature. By cross-referencing results of electron microscopy and X-ray spectroscopy together with electrochemical analysis, the effects of heat treatment under CO-reductive and O2-oxidative conditions towards FAOR were schematically elucidated. Of special relevance, the mass activity (MA) of PdPt-CO, PdPt-O2, PdRuPt-CO, and PdRuPt-O2 NCs is 1.7/2.0, 1.3/2.2, 1.1/5.5, and 0.9/4.7 Amg-1 in the anodic/cathodic scan, respectively, which is 2~4-folds improved comparative to of as-prepared PdPt (1.0/1.9 Amg-1 in anodic/cathodic scan, respectively) and PdRuPt (0.9/1.4 Amg-1 in anodic/cathodic scan, respectively) NCs. Meanwhile, after chronoamperometric (CA) stability test up to 2000 s, PdPt-CO (72 mAmg-1) and PdRuPt-CO (213 mAmg-1) NCs exhibit higher MA compared to as-prepared PdPt (54 mAmg-1) and PdRuPt (62 mAmg-1) NCs, which is attributed to the increase of surface Pt composition, especially for PdRuPt-CO NC. Besides, the stability of PdPt-O2 (15 mAmg-1) and PdRuPt-O2 (22 mAmg-1) NCs is deteriorated as compared to that of as-prepared NCs due to severe oxidation in O2 atmosphere. Of utmost importance, we developed a ternary PdRuPt catalyst with ultra-low Pt content (~2 wt.%) and significantly improved FAOR performance than pure Pt catalysts. Moreover, we demonstrated that the FAOR performance can be further enhanced by more than 30% via a unique CO annealing treatment.

Tunable Periodically Ordered Mesoporosity in Palladium Membranes Enables Exceptional Enhancement of Intrinsic Electrocatalytic Activity for Formic Acid Oxidation

Developing superior electrocatalysts for formic acid oxidation (FAO) is the most crucial step in commercializing direct formic acid fuel cells. Herein, we electrodeposited palladium membranes with periodically ordered mesoporosity obtained by asymmetrically replicating the bicontinuous cubic phase structure of a lyotropic liquid-crystal template. The Pd membrane with the largest periodicity and highest degree of order delivered up to 90.5 m²  g^-1 of electrochemical active surface area and 3.34 A mg^-1 electrocatalysis capability towards FAO, 3.8 and 7.8 times the values of the commercial Pd/C catalyst, respectively. By controlling the temperature and potential of the electrodeposition procedure, the periodicity area and order degree of the mesoporosity are highly tunable. These Pd membranes gave prototype formic acid fueled cells with 4.3 and 2.4 times the maximum current and power density of the commercial Pd/C catalyst.

Polyol assisted formaldehyde reduction of bi-metallic Pt-Pd supported agro-waste derived carbon spheres as an efficient electrocatalyst for formic acid and ethylene glycol oxidation

This report explains, (i) the preparation of carbon spheres (CS) from agro-waste through hydrothermal carbonization (HTC) followed by high temperature carbonization, (ii) the decoration of bi-metallic Pt-Pd nanoparticles (Pt-Pd NPs) with different compositions (Pt/C, Pt_0.5Pd₁/C, Pt₁Pd₁/C and Pt₁Pd_0.5/C, Pd/C) on the carbon by ethylene glycol solvated polyol assisted formaldehyde reduction method and (iii) subsequently used as the electrocatalyst for formic acid (FA) and ethylene glycol (EG) electro-oxidation. The structural and morphological properties of the electrocatalysts were studied using advanced physicochemical characterization techniques. The obtained results well evidence the homogeneous dispersion of Pt-Pd NPs on the surface of the carbon. Especially, Pt_0.5Pd₁/C exhibited excellent electrocatalytic property towards formic acid electro-oxidation reaction (FAOR) with a higher current density (256 mA cm^-2) and stability due to "third body effect". On the other hand, Pt₁Pd_0.5/C expressed superior electrochemical performance towards ethylene glycol electro-oxidation reaction (EGOR) due to the strong interaction between high Pt content and Pd. Hence, this work reveals the improved electrocatalytic performance of bi-metallic Pt-Pd NPs supported biomass-derived carbon as a promising anodic electrocatalyst towards FAOR and EGOR.

PdxFey alloy nanoparticles decorated on carbon nanofibers with improved electrocatalytic activity for ethanol electrooxidation in alkaline media

We prepared bimetallic Pd_xFe_y alloy nanoparticles/carbon nanofiber composites with different Pd/Fe mole ratios and showed their advantage as a potential anode catalyst in ethanol fuel cells.

Synthesis, growth mechanisms, and applications of palladium-based nanowires and other one-dimensional nanostructures

Palladium-based nanostructures have attracted the attention of researchers due to their useful catalytic properties and unique ability to form hydrides, which finds application in hydrogen storage and hydrogen detection. Palladium-based nanowires have some inherent advantages over other Pd nanomaterials, combining high surface-to-volume ratio with good thermal and electron transport properties, and exposing high-index crystal facets that can have enhanced catalytic activity. Over the past two decades, both synthesis methods and applications of 1D palladium nanostructures have advanced greatly. In this review, we start by discussing different types of 1D palladium nanostructures before moving on to the different synthesis approaches that can produce them. Next, we discuss factors including kinetic vs. thermodynamic control of growth, oxidative etching, and surface passivation that affect palladium nanowire synthesis. We also review efforts to gain insight into growth mechanisms using different characterization tools. We discuss the effects of concentration of capping agents, reducing agents, metal halides, pH, and sacrificial oxidation on the growth of Pd-based nanowires in solution, from shape control, to yield, to aspect ratio. Various applications of palladium and palladium alloy nanowires are then discussed, including electrocatalysis, hydrogen storage, and sensing of hydrogen and other chemicals. We conclude with a summary and some perspectives on future research directions for this category of nanomaterials.

Perforated Pd Nanosheets with Crystalline/Amorphous Heterostructures as a Highly Active Robust Catalyst toward Formic Acid Oxidation

Perforated ultrathin Pd nanosheets with crystalline/amorphous heterostructures are rationally synthesized to offer a large electrochemically active surface area of 172.6 m² g^-1 and deliver a 5.6 times higher apparent reaction rate in comparison to commercial Pd/C, thus offering a facile confined growth method to generate superior catalysts.

Bifunctional Oxygen Electrocatalysis of N, S-Codoped Porous Carbon with Interspersed Hollow CoO Nanoparticles for Rechargeable Zn-Air Batteries

Exploring efficient bifunctional oxygen electrocatalysts is beneficial to promote the practical applications for rechargeable Zn-air batteries. Herein, a high-efficiency one-pot method is developed to synthesize porous carbon with N, S doping and embedded hollow cobalt oxide nanoparticles. The coordination of polyethyleneimine molecules with cobalt ions enables the formation of organic-inorganic precursors via the co-precipitation with lignosulfonate because of the electrostatic interaction. Under thermal treatment, the hollow cobalt oxide nanoparticles can be well dispersed among the carbon matrix codoped with N, S. The as-prepared composite catalysts exhibit efficient bifunctional activity for electrochemical reduction and evolution reactions of oxygen, thanks to the N, S codoping nature and the hollow cobalt oxide with abundant oxygen vacancies. The bifunctional catalytic activity renders the assembly of high-performance Zn-air battery in an aqueous electrolyte with a specific capacity of 745 mA h g_Zn^-1 and good cycling stability for over 100 h. More importantly, the all-solid-state Zn-air battery is assembled with a polymer-based electrolyte, also exhibiting good cycling stability and flexibility under various bending status.

Clean synthesis of RGO/Mn3O4 nanocomposite with well-dispersed Pd nanoparticles as a high-performance catalyst for hydroquinone oxidation

In this study, a well-dispersed Pd nanoparticle (NP)-supported RGO/Mn₃O₄ (G/M/Pd) composite was synthesized by a clean synthetic route, where galvanic replacement reaction simply occurred between Mn₃O₄ and a palladium salt, thereby avoiding the use of harsh reducing and capping agents. The G/M/Pd composite served as a robust catalyst for the catalytic oxidation of hydroquinone (HQ) to benzoquinone (BQ) with H₂O₂ in an aqueous solution. Oxidation was completed in only 4 min, with a turnover frequency (TOF) of 3613 h^-1; this TOF is one hundred times those of previously reported Pd- and Ag-based catalysts. The superior performance was related to the electronic inductive effect between Mn₃O₄ and Pd NPs, which was verified by density functional theory calculations. Trapping experiments revealed that the oxidation of HQ was considerably related to the ·OH radicals generated from the decomposition of H₂O₂. In addition, the influencing factors were further investigated, including catalyst and HQ concentrations, solution pH, solvents, and various inorganic and organic interferences. Moreover, the G/M/Pd catalyst exhibits diverse applications for the catalytic oxidation of HQ derivatives with high TOFs.

Two-Dimensional Zeolitic Imidazolate Framework-L-Derived Iron-Cobalt Oxide Nanoparticle-Composed Nanosheet Array for Water Oxidation

Rational design of various functional nanomaterials using MOFs as a template provides an effective strategy to synthesize electrocatalysts for water splitting. In this work, we reported that an iron-cobalt oxide with 2D well-aligned nanoflakes assembling on carbon cloth (Fe-Co₃O₄ NS/CC), fabricated by an anion-exchange reaction followed by an annealing process, could serve as a high-performance oxygen-evolving catalyst. Specifically, the zeolitic imidazolate framework-L-Co nanosheet array (ZIF-L-Co NS/CC) was synthesized through a facile ambient liquid-phase deposition reaction, and then reacted with [Fe(CN)₆]^3- ions as precursors during the anion-exchange reaction at room temperature. Finally, the Fe-Co₃O₄ NS/CC was obtained via annealing treatment. On account of the compositional and structural superiority, this 3D monolithic anode exhibited outstanding electrocatalytic performance with a low overpotential of 290 mV to obtain a geometrical current density of 10 mA cm^-2 and good durability for water oxidation in base.

New Anode Material for Lithium-Ion Batteries: Aluminum Niobate (AlNb11O29)

This paper describes the syntheses and electrochemical properties of a new niobate compound, aluminum niobate (AlNb₁₁O₂₉), for Li⁺ storage. AlNb₁₁O₂₉-microsized particles and nanowires were synthesized based on the solid-state reaction and solvothermal methods, respectively. In situ X-ray diffraction results confirmed the intercalating mechanism of Li⁺ in AlNb₁₁O₂₉ and revealed its high structural stability against cycling. The AlNb₁₁O₂₉ nanowires with a novel bamboo-like morphology afforded a large interfacial area and short charge transport pathways, thus leading to the observed excellent electrochemical properties, including high reversible Li⁺-storage capacity (266 mA h g^-1), safe operating potential (around 1.68 V), and high initial Coulombic efficiency (93.3%) at 0.1 C. At a very high rate (10 C), the AlNb₁₁O₂₉ nanowires still exhibited a capacity as high as 192 mA h g^-1, indicating their good rate capability. In addition, at 10 C, 96.3% capacity was retained over 500 cycles, indicating superior cycling stability. A full cell fabricated with AlNb₁₁O₂₉ nanowires as the anode and LiNi_0.5Mn_1.5O₄ microparticles as the cathode delivered a high energy density of 390 W h kg^-1 at 0.1 C. This work suggests that the AlNb₁₁O₂₉ nanowires hold a great promise for the development of high-performance lithium-ion batteries for large-scale energy-storage applications.

Nanorod Array of SnO2 Quantum Dot Interspersed Multiphase TiO2 Heterojunctions with Highly Photocatalytic Water Splitting and Self-Rechargeable Battery-Like Applications

The ever-growing demand for sustainable and renewable power sources has led to the development of novel materials for photocatalytic water splitting, but enhancing the photocatalytic efficiency remains a core problem. Herein, we report a conceptual effective and experimental confirmed strategy for SnO₂ quantum dot (QD) interspersed multiphase (rutile, anatase) TiO₂ nanorod arrays (SnO₂/RA@TiO₂ NRs) to immensely enhance the carrier separation for highly efficient water splitting by merging simultaneously the QD, multiphase, and heterojunction approaches. Under this synergistic effect, a doping ratio of 25% SnO₂ QD interspersed into multiphase TiO₂ NRs exhibited a superior optical adsorption and excellent photocurrent density (2.45 mA/cm² at 1.0 V), giving rise to a largely enhanced incident light to current efficiency in the UV region (45-50%). More importantly, this material-based device can act as power supply with a voltage of ∼2.8 V after illumination, which can automatically self-recharge by reacting with oxygen vacancy and water molecule to realize reuse. The current study provides a new paradigm about heightening the carrier separation extent of QD interspersed multiphase heterojunctions, fabricating a new solar-energy-converting material/device, and achieving a highly photocatalytic water splitting/self-charging battery-like application.