Deposition of Atomically Thin Pt Shells on Amorphous Palladium Phosphide Cores for Enhancing the Electrocatalytic Durability

Dynamic modulation of electron redistribution at the heterogeneous interface nickel hydroxides/platinum boosts acidic oxygen reduction reaction

The interfacial electron interactions in heterogeneous catalysts are critical in determining the adsorption strengths and configurations of reaction intermediates, which are essential for the efficiency of multistep tandem catalytic processes. Amorphous-crystalline (a-c) heterostructures have garnered significant interest due to their unusual atomic arrangements, adaptable electron configurations, and exceptional stability. Here, we introduce a mesoporous a-c heterojunction catalyst featuring enriched amorphous-crystalline Ni(OH)2/Pt boundaries (ac-Ni(OH)2@m-Pt), designed for efficient acidic oxygen reduction reaction (ORR). This catalyst enables electron redistribution at the heterogeneous interface, thereby enhancing both catalytic activity and durability. As anticipated, the ac-Ni(OH)2@m-Pt delivers a high mass activity (MA) of 0.95 A mgPt-1 and maintains good durability (89.8% MA retention) over 15000 cycles. Advanced characterization and theoretical calculations reveal that the catalyst's high performance stems from the dynamic heterogeneous-interface electron redistribution at the a-c interface. This dynamic-cycling electron transfer, driven by the applied potential, promotes O2 activation and accelerates the protonation of *O intermediate during ORR. This work offers a promising avenue for improving the design of electrocatalysts using a-c interface engineering.

Highly-Branched PtCu Nanocrystals with Low-Coordination for Enhanced Oxygen Reduction Catalysis

Low-coordination platinum-based nanocrystals emanate great potential for catalyzing the oxygen reduction reactions (ORR) in fuel cells, but are not widely applied owing to poor structural stability. Here, several PtCu nanocrystals (PtCu NCs) with low coordination numbers were prepared via a facile one-step method, while the desirable catalyst structures were easily obtained by adjusting the reaction parameters. Wherein, the Pt1Cu1 NCs catalyst with abundant twin boundaries and high-index facets displays 15.25 times mass activity (1.647 A mgPt -1 at 0.9 VRHE) of Pt/C owing to the abundant effective active sites, low-coordination numbers and appropriate compressive strain. More importantly, the core-shell and highly developed dendritic structures in Pt1Cu1 NCs catalyst give it an extremely high stability with only 17.2% attenuation of mass activity while 61.1% for Pt/C after the durability tests (30 000 cycles). In H2-O2 fuel cells, Pt1Cu1 NCs cathode also exhibits a higher peak power density and a longer-term lifetime than Pt/C cathode. Moreover, theoretical calculations imply that the weaker adsorption of intermediate products and the lower formation energy barrier of OOH* in Pt1Cu1 NCs collaboratively boost the ORR process. This work offers a morphology tuning approach to prepare and stabilize the low-coordination platinum-based nanocrystals for efficient and stable ORR.

Amorphous RuPd bimetallene for hydrogen evolution reaction in acidic and alkaline conditions: a first-principles study

Metallene materials can provide a large number of active catalytic sites for the efficient use of noble metals as catalysts for hydrogen evolution reaction (HER), whereas the intrinsic activity on the surface is insufficient in crystal phase. The amorphous phase with an inherent long-range disorder can offer a rich coordinate environment and charge polarization on the surface is proposed for promoting the intrinsic catalytic activity on the surface of noble metals. Herein, we designed an amorphous RuPd (am-RuPd) structure by the first principles molecular dynamics method. The performance of the acidic HER on am-RuPd can have a huge enhancement due to the free energy change of hydrogen adsorption close to zero. In alkaline conditions, the H2O dissociation energy barrier on am-RuPd is just 0.49 eV, and it is predicted that the alkaline HER performance of am-RuPd will largely exceed that of Pt nanocrystalline sheets. This work provides a strategy for enhancing the intrinsic catalytic activity on the surface and a way to design an efficient HER catalyst based on metallene materials used in both acidic and alkaline conditions.

Heteroatom Doping Promoting CoP for Driving Water Splitting

CoP nanomaterials have been extensively regarded as one of the most promising electrocatalysts for overall water splitting due to their unique bifunctionality. Although the great promise for future applications, some important issues should also be addressed. Heteroatom doping has been widely acknowledged as a potential strategy for improving the electrocatalytic performance of CoP and narrowing the gap between experimental study and industrial applications. Recent years have witnessed the rapid development of heteroatom-doped CoP electrocatalysts for water splitting. Aiming to provide guidance for the future development of more effective CoP-based electrocatalysts, we herein organize a comprehensive review of this interesting field, with the special focus on the effects of heteroatom doping on the catalytic performance of CoP. Additionally, many heteroatom-doped CoP electrocatalysts for water splitting are also discussed, and the structure-activity relationship is also manifested. Finally, a systematic conclusion and outlook is well organized to provide direction for the future development of this interesting field.

Nature-Derived Hollow Micron-Tubular Signal Tracers Conquering the Size Limitations for Multimodal Immunochromatographic Detection of Antibiotics

Developing signal tracers (STAs) with large size, multifunctionality, and high retention bioaffinity is believed to be a potential solution for achieving high-performance immunochromatographic assays (ICAs). However, the size limitations of STAs on strips are always a challenge because of the serious steric hindrance. Here, based on metal-quinone coordination and further metal etching, hollow micron-tubular STAs formed by natural alizarin and Fe3+ ions (named ALIFe) are produced to break through size limitations, provide more active sites, and achieve three-mode ICAs (ALIFe STAs-ICAs). Thanks to the special tubular morphology, ALIFe can successfully pass through the strip and provide an ideal signal intensity within 7 min at low mAb and probe dosages to achieve stable ICA analysis. Importantly, ALIFe shows excellent antibody enrichment and bioaffinity retention capability. With a proof-of-concept for streptomycin, the ALIFe STAs-ICAs showed the limit of detection (LOD) at 0.39 ng mL-1 for colorimetric mode, 0.32 ng mL-1 for catalytic mode, and 0.016 ng mL-1 for photothermal mode with total recoveries ranging from 80.46 to 121.59% in mike and honey samples. We anticipate that our study will help expand the ideas for the design of high-performance STAs with large size and broaden the practical application of ICA.

Recent Progress on Phase Engineering of Nanomaterials

As a key structural parameter, phase depicts the arrangement of atoms in materials. Normally, a nanomaterial exists in its thermodynamically stable crystal phase. With the development of nanotechnology, nanomaterials with unconventional crystal phases, which rarely exist in their bulk counterparts, or amorphous phase have been prepared using carefully controlled reaction conditions. Together these methods are beginning to enable phase engineering of nanomaterials (PEN), i.e., the synthesis of nanomaterials with unconventional phases and the transformation between different phases, to obtain desired properties and functions. This Review summarizes the research progress in the field of PEN. First, we present representative strategies for the direct synthesis of unconventional phases and modulation of phase transformation in diverse kinds of nanomaterials. We cover the synthesis of nanomaterials ranging from metal nanostructures such as Au, Ag, Cu, Pd, and Ru, and their alloys; metal oxides, borides, and carbides; to transition metal dichalcogenides (TMDs) and 2D layered materials. We review synthesis and growth methods ranging from wet-chemical reduction and seed-mediated epitaxial growth to chemical vapor deposition (CVD), high pressure phase transformation, and electron and ion-beam irradiation. After that, we summarize the significant influence of phase on the various properties of unconventional-phase nanomaterials. We also discuss the potential applications of the developed unconventional-phase nanomaterials in different areas including catalysis, electrochemical energy storage (batteries and supercapacitors), solar cells, optoelectronics, and sensing. Finally, we discuss existing challenges and future research directions in PEN.

Sub-Monolayer SbOx on PtPb/Pt Nanoplate Boosts Direct Formic Acid Oxidation Catalysis

To promote the commercialization of direct formic acid fuel cell (DFAFC), it is vital to explore new types of direct formic acid oxidation (FAOR) catalysts with high activity and direct pathway. Here, we report the synthesis of intermetallic platinum-lead/platinum nanoplates inlaid with sub-monolayer antimony oxide surface (PtPb/Pt@sub-SbOx NPs) for efficient catalytic applications in FAOR. Impressively, they can achieve the remarkable FAOR specific and mass activities of 28.7 mA cm-2 and 7.2 A mgPt-1, which are 151 and 60 times higher than those of the state-of-the-art commercial Pt/C, respectively. Furthermore, the X-ray photoelectron spectroscopy and X-ray absorption spectroscopy results collectively reveal the optimization of the local coordination environment by the surface sub-monolayer SbOx, along with the electron transfer from Pb and Sb to Pt, driving the predominant dehydrogenation process. The sub-monolayer SbOx on the surface can effectively attenuate the CO generation, largely improving the FAOR performance of PtPb/Pt@sub-SbOx NPs. This work develops a class of high-performance Pt-based anodic catalyst for DFAFC via constructing the unique intermetallic core/sub-monolayer shell structure.

Ultrathin Co-N-C Layer Modified Pt-Co Intermetallic Nanoparticles Leading to a High-Performance Electrocatalyst toward Oxygen Reduction and Methanol Oxidation

The development of low platinum-based alloy electrocatalysts is crucial to accelerate the commercialization of fuel cells, yet remains a synthetic challenge and an incompatibility between activity and stability. Herein, a facile procedure to fabricate a high-performance composite that comprises Pt-Co intermetallic nanoparticles (IMNs) and Co, N co-doped carbon (Co-N-C) electrocatalyst is proposed. It is prepared by direct annealing of homemade carbon black-supported Pt nanoparticles (Pt/KB) covered with a Co-phenanthroline complex. During this process, most of Co atoms in the complex are alloyed with Pt to form ordered Pt-Co IMNs, while some Co atoms are atomically dispersed and doped in the framework of superthin carbon layer derived from phenanthroline, which is coordinated with N to form Co-Nx moieties. Moreover, the Co-N-C film obtained from complex is observed to cover the surface of Pt-Co IMNs, which prevent the dissolution and agglomeration of nanoparticles. The composite catalyst exhibits high activity and stability toward oxygen reduction reactions (ORR) and methanol oxidation reactions (MOR), delivering outstanding mass activities of 1.96 and 2.92 A mgPt -1 for ORR and MOR respectively, owing to the synergistic effect of Pt-Co IMNs and Co-N-C film. This study may provide a promising strategy to improve the electrocatalytic performance of Pt-based catalysts.

Strain and Surface Engineering of Multicomponent Metallic Nanomaterials with Unconventional Phases

Multicomponent metallic nanomaterials with unconventional phases show great prospects in electrochemical energy storage and conversion, owing to unique crystal structures and abundant structural effects. In this review, we emphasize the progress in the strain and surface engineering of these novel nanomaterials. We start with a brief introduction of the structural configurations of these materials, based on the interaction types between the components. Next, the fundamentals of strain, strain effect in relevant metallic nanomaterials with unconventional phases, and their formation mechanisms are discussed. Then the progress in surface engineering of these multicomponent metallic nanomaterials is demonstrated from the aspects of morphology control, crystallinity control, surface modification, and surface reconstruction. Moreover, the applications of the strain- and surface-engineered unconventional nanomaterials mainly in electrocatalysis are also introduced, where in addition to the catalytic performance, the structure-performance correlations are highlighted. Finally, the challenges and opportunities in this promising field are prospected.

A General Strategy for Synthesis of Binary Transition Metal Phosphides Hollow Sandwich Heterostructures

The hollow sandwich core-shell micro-nanomaterials are widely used in materials, chemistry, and medicine, but their fabrication, particularly for transition metal phosphides (TMPs), remains a great challenge. Herein, a general synthesis strategy is presented for binary TMPs hollow sandwich heterostructures with vertically interconnected nanosheets on the inside and outside surfaces of polyhedron FeCoP_x /C, demonstrated by a variety of transition metals (including Co, Fe, Cd, Mn, Cu, Cr, and Ni). Density functional theory (DFT) calculation reveals the process and universal mechanism of layered double hydroxide (LDH) growth on Prussian blue analog (PBA) surface in detail for the first time, which provides the theoretical foundations for feasibility and rationality of the synthesis strategy. This unique structure exhibits a vertical nanosheet-shell-vertical nanosheet configuration combining the advantages of sandwich, hollow and vertical heterostructures, effectively achieving their synergistic effect. As a proof-of-concept of their applications, the CoNiP_x @FeCoP_x /C@CoNiP_x hollow sandwich polyhedron architectures (representative samples) show excellent catalytic performance for the oxygen evolution reaction (OER) in alkaline electrolytes. This work provides a general method for constructing hollow-sandwich micro-nanostructures, which provides more ideas and directions for design of micro-nano materials with special geometric topology.

Strategies for Promoting Catalytic Performance of Ru-based Electrocatalysts towards Oxygen/Hydrogen Evolution Reaction

Ru-based materials hold great promise for substituting Pt as potential electrocatalysts toward water electrolysis. Significant progress is made in the fabrication of advanced Ru-based electrocatalysts, but an in-depth understanding of the engineering methods and induced effects is still in their early stage. Herein, we organize a review that focusing on the engineering strategies toward the substantial improvement in electrocatalytic OER and HER performance of Ru-based catalysts, including geometric structure, interface, phase, electronic structure, size, and multicomponent engineering. Subsequently, the induced enhancement in catalytic performance by these engineering strategies are also elucidated. Furthermore, some representative Ru-based electrocatalysts for the electrocatalytic HER and OER applications are also well presented. Finally, the challenges and prospects are also elaborated for the future synthesis of more effective Ru-based catalysts and boost their future application.

Pd-Based Metallenes for Fuel Cell Reactions

Pd-based metallenes, atomically thin layers composed primarily of under-coordinated Pd atoms, have emerged as the newest members in the family of two-dimensional (2D) nanomaterials. Moreover, the unique physiochemical properties, high intrinsic activity associated with metallenes coupled with the ease of applying chemical modifications result in great potential in catalyst engineering for fuel cell reactions. Especially in recent years, interest in Pd-based metallenes is growing, as evidenced by surge in available literatures. Herein, we have reviewed the recent findings achieved in Pd-based metallenes in fuel cells by highlighting the technologies available for deriving metallenes and manifesting the modification strategies for designing them to better suit the application demand. Moreover, we also discuss the perspective insights of Pd-based metallenes for fuel cells regarding the surfactant-free synthesis method, strain engineering, constructing high-entropy alloy, and so on.

Synthesis of amorphous trimetallic PdCuNiP nanoparticles for enhanced OER

Metal phosphides with multi-element components and amorphous structure represent a novel kind of electrocatalysts for promising activity and durability towards the oxygen evolution reaction (OER). In this work, a two-step strategy, including alloying and phosphating processes, is reported to synthesize trimetallic amorphous PdCuNiP phosphide nanoparticles for efficient OER under alkaline conditions. The synergistic effect between Pd, Cu, Ni, and P elements, as well as the amorphous structure of the obtained PdCuNiP phosphide nanoparticles, would boost the intrinsic catalytic activity of Pd nanoparticles towards a wide range of reactions. These obtained trimetallic amorphous PdCuNiP phosphide nanoparticles exhibit long-term stability, nearly a 20-fold increase in mass activity toward OER compared with the initial Pd nanoparticles, and 223 mV lower in overpotential at 10 mA cm^-2. This work not only provides a reliable synthetic strategy for multi-metallic phosphide nanoparticles, but also expands the potential applications of this promising class of multi-metallic amorphous phosphides.

Pt-Sn alloy shells with tunable composition and structure on Au nanoparticles for boosting ethanol oxidation

Combining the core-shell structure with the optimization of surface composition and structure in the shell is a fantastic strategy to enhance the electrocatalytic performances. Here, we synthesized trimetallic Au@Pt_xSn_y core-shell nanoparticles (NPs) with tunable composition and structure of Pt-Sn alloyed shells. Impressively, the Au@PtSn core-shell NPs with hexagonal PtSn alloyed shells exhibited the highest mass activity and specific activity toward ethanol oxidation reaction (EOR) in alkaline electrolyte, which are 13.0 and 12.7 times higher than those of the commercial Pt/C. In addition, the Au@PtSn core-shell NPs displayed the best stability compared to commercial Pt/C, with only 44.8% loss vs. 86.8% loss in mass activity after 1,000 s due to the stronger anti-poisoning ability for reaction intermediates. The theory calculations reveal that the introduction of Au core and alloying Pt with Sn both endow Pt with an appropriate d-band center, and thus effectively boosting the EOR activity.

Noble Metal-Based Catalysts with Core-Shell Structure for Oxygen Reduction Reaction: Progress and Prospective

With the deterioration of the ecological environment and the depletion of fossil energy, fuel cells, representing a new generation of clean energy, have received widespread attention. This review summarized recent progress in noble metal-based core-shell catalysts for oxygen reduction reactions (ORRs) in proton exchange membrane fuel cells (PEMFCs). The novel testing methods, performance evaluation parameters and research methods of ORR were briefly introduced. The effects of the preparation method, temperature, kinds of doping elements and the number of shell layers on the ORR performances of noble metal-based core-shell catalysts were highlighted. The difficulties of mass production and the high cost of noble metal-based core-shell nanostructured ORR catalysts were also summarized. Thus, in order to promote the commercialization of noble metal-based core-shell catalysts, research directions and prospects on the further development of high performance ORR catalysts with simple synthesis and low cost are presented.

Gram-Scale Synthesis of Carbon-Supported Sub-5 nm PtNi Nanocrystals for Efficient Oxygen Reduction

The preparation of a high performance and durability with low-platinum (Pt) loading oxygen reduction catalysts remains a challenge for the practical application of fuel cells. Alloying Pt with a transition metal can greatly improve the activity and durability for oxygen reduction reaction (ORR). In this work, we present a one-pot wet-chemical strategy to controllably synthesize carbon supported sub-5 nm PtNi nanocrystals with a ~3% Pt loading. The as-prepared PtNi/C-200 catalyst with a Pt/Ni atomic ratio of 2:3 shows a high oxygen reduction activity of 0.66 A mgpt−1 and outstanding durability over 10,000 potential cycles in 0.1 M KOH in a half-cell condition. The PtNi/C-200 catalyst exhibits the highest ORR activity, with an onset potential (Eonset) of 0.98 V and a half-wave potential (E1/2) of 0.84 V. The mass activity and specific activity are 3.89 times and 9.16 times those of 5% commercial Pt/C. More importantly, this strategy can be applied to the gram-scale synthesis of high-efficiency electrocatalysts. As a result, this effective synthesis strategy has a significant meaning in practical applications of full cells.

Unveiling the Synergistic Effects of Monodisperse Sea Urchin-like PdPb Alloy Nanodendrites as Stable Electrocatalysts for Ethylene Glycol and Glycerol Oxidation Reactions

In recent times, the fabrication of noble metal-based catalysts with controllable morphologies has become a research hotspot. Electrocatalytic devices with excellent catalytic performance and enhanced durability for the ethylene glycol oxidation reaction (EGOR) and the glycerol oxidation reaction (GOR) are significant for commercial direct fuel cells. Herein, a series of PdPb sea urchin-like nanodendrite (ND) structures with controllable molar ratios were synthesized as EGOR and GOR electrocatalysts of high efficiency. The optimized structurally regular Pd₃Pb NDs exhibit the best electrocatalytic activity and outstanding stability compared to other samples and commercial Pt/C. In addition, the integrated Pb on Pd₃Pb NDs can mitigate the bond energy the intermediates generate and further boost the electrooxidation of the intermediates by supplying enough active sites without considering its intrinsic structure, which is beneficial to the enhanced EGOR and GOR activity and stability. With the assistance of electrochemical measurement, the mechanism of the enhanced alloy was further investigated. This paper presents a promising strategy to fabricate catalysts with stable structures, which will elucidate a very promising approach for developing Pd-based catalysts for further applications in fuel cells.

Hydrogen-Intercalation-Induced Lattice Expansion of Pd@Pt Core-Shell Nanoparticles for Highly Efficient Electrocatalytic Alcohol Oxidation

Lattice engineering on specific facets of metal catalysts is critically important not only for the enhancement of their catalytic performance but also for deeply understanding the effect of facet-based lattice engineering on catalytic reactions. Here, we develop a facile two-step method for the lattice expansion on specific facets, i.e., Pt(100) and Pt(111), of Pt catalysts. We first prepare the Pd@Pt core-shell nanoparticles exposed with the Pt(100) and Pt(111) facets, respectively, via the Pd-seeded epitaxial growth, and then convert the Pd core to PdH_0.43 by hydrogen intercalation. The lattice expansion of the Pd core induces the lattice enlargement of the Pt shell, which can significantly promote the alcohol oxidation reaction (AOR) on both Pt(100) and Pt(111) facets. Impressively, Pt mass specific activities of 32.51 A mg_Pt^-1 for methanol oxidation and 14.86 A mg_Pt^-1 for ethanol oxidation, which are 41.15 and 25.19 times those of the commercial Pt/C catalyst, respectively, have been achieved on the Pt(111) facet. Density functional theory (DFT) calculations indicate that the remarkably improved catalytic performance on both the Pt(100) and the Pt(111) facets through lattice expansion arises from the enhanced OH adsorption. This work not only paves the way for lattice engineering on specific facets of nanomaterials to enhance their electrocatalytic activity but also offers a promising strategy toward the rational design and preparation of highly efficient catalysts.

PtPdCu cubic nanoframes as electrocatalysts for methanol oxidation reaction

PtPdCu cubic nanoframes with unique open architecture exhibit excellent electrocatalytic performances toward methanol electrooxidation.