Thermodynamic Origin-Based In Situ Electrochemical Construction of Reversible p-n Heterojunctions for Optimal Stability in Potassium Ion Storage.

Heterojunctions in electrode materials offer diverse improvements during the cycling process of energy storage devices, such as volume change buffering, accelerated ion/electron transfer, and better electrode structure integrity, however, obtaining optimal heterostructures with nanoscale domains remains challenging within constrained materials. A novel in situ electrochemical method is introduced to develop a reversible CuSe/PSe p-n heterojunction (CPS-h) from Cu3 PSe4 as starting material, targeting maximum stability in potassium ion storage. The CPS-h formation is thermodynamically favorable, characterized by its superior reversibility, minimized diffusion barriers, and enhanced conversion post K+ interaction. Within CPS-h, the synergy of the intrinsic electric field and P-Se bonds enhance electrode stability, effectively countering the Se shuttling phenomenon. The specific orientation between CuSe and PSe leads to a 35° lattice mismatch generates large space at the interface, promoting efficient K ion migration. The Mott-Schottky analysis validates the consistent reversibility of CPS-h, underlining its electrochemical reliability. Notably, CPS-h demonstrates a negligible 0.005% capacity reduction over 10,000 half-cell cycles and remains stable through 2,000 and 4,000 cycles in full cells and hybrid capacitors, respectively. This study emphasizes the pivotal role of electrochemical dynamics in formulating highly stable p-n heterojunctions, representing a significant advancement in potassium-ion battery (PIB) electrode engineering.

Boosting Manganese Selenide Anode for Superior Sodium-Ion Storage via Triggering α → ß Phase Transition.

Sodium-ion batteries (SIBs) have been extensively studied owing to the abundance and low-price of Na resources. However, the infeasibility of graphite and silicon electrodes in sodium-ion storage makes it urgent to develop high-performance anode materials. Herein, α-MnSe nanorods derived from δ-MnO2 (δ-α-MnSe) are constructed as anodes for SIBs. It is verified that α-MnSe will be transferred into ß-MnSe after the initial Na-ion insertion/extraction, and δ-α-MnSe undergoes typical conversion mechanism using a Mn-ion for charge compensation in the subsequent charge-discharge process. First-principles calculations support that Na-ion migration in defect-free α-MnSe can drive the lattice distortion to phase transition (alpha → beta) in thermodynamics and dynamics. The formed ß-MnSe with robust lattice structure and small Na-ion diffusion barrier boosts great structure stability and electrochemical kinetics. Hence, the δ-α-MnSe electrode contributes excellent rate capability and superior cyclic stability with long lifespan over 1000 cycles and low decay rate of 0.0267% per cycle. Na-ion full batteries with a high energy density of 281.2 Wh·kg-1 and outstanding cyclability demonstrate the applicability of δ-α-MnSe anode.

Oxygen Vacancy-Tailored Schottky Heterojunction Activates Interface Dipole Amplification and Carrier Inversion for High-Performance Potassium-Ion Batteries.

An oxygen vacancy-tailored Schottky heterostructure composed of polyvinylpyrrolidone-assisted Bi2 Sn2 O7 (PVPBSO) nanocrystals and moderate work function graphene (mWFG, WF = 4.36 eV) is designed, which in turn intensifies the built-in voltage and interface dipole across the space charge region (SCR), leading to the inversion of majority carriers for facilitating K+ transport/diffusion behaviors. Thorough band-alignment experiments and interface simulations reveal the dynamics between deficient BSO and mWFG, and how charge redistribution within the SCR leads to carrier inversion, demonstrating the impact of different defect engineering degrees on the amplification of Schottky junctions. The ordered transport of bipolar carriers can boost electrons and K ions easily passing through the inner and outer surfaces of the heterostructure. With high activity and low resistance in electrochemical reactions, the PVPBSO/mWFG exhibits an attractive capacity of 430 mA h g-1 and a rate capability exceeding 2000 mA g-1 , accompanied by minimal polarization and efficient utilization of conversion-alloying reactions. The substantial cell capacity and high-redox plateau of PVPBSO/mWFG//PB contribute to the practical feasibility of high-energy full batteries, offering long-cycle retention and high-voltage output. This study emphasizes the direct importance of interface and junction engineering in improving the efficiency of diverse electrochemical kinetic and diffusion processes for potassium-ion batteries.

3D space-confined Co0.85Se architecture with effective interfacial stress relaxation as anode material reveals robust and highly loading potassium-ion batteries.

Conversion-type transition metal chalcogenide anodes could bring relatively high specific capacity in potassium ion storage due to multiple electron transport reactions, but often accompanying huge volume changes and resulting in low cycle life and rapid capacity fading.While electrode materials are closely packed, the contact at the interface during potassiation/depotassiation is similar to point-to-point contact, generating strong stress to make self-aggregation occur. In this work, we constructed a 3D carbon framework to confine Co0.85Se nanocrystals in three-dimensional space, both fulfilling the requirements of the material's size in the nano-scale and providing the largest contact area for releasing stress. With this optimization, nitrogen-doped carbon confined Co0.85Se nanocrystals (Co0.85Se@NC) reach an ultra-stable cycle life over 4000 times with a specific capacity of 190.9 mA h g-1 at 500 mA g-1 and provide 155.6 mA h g-1 at 10 A g-1 in the rate capability test. It also renders the areal capacity up to 1.03 mA h cm-2 at 500 mA g-1 in the high-mass loading test. Furthermore, based on the finite element analysis, the 3D confinement strategy has the lowest interfacial stress, ensuring Co0.85Se nanocrystals with high structural integrity. This strategy can relieve the stress issue in the conversion-type anode and demonstrate superior electrochemical performance even at high-loading mass electrodes.

Electrochemical Self-Healing Nanocrystal Electrodes for Ultrastable Potassium-Ion Storage.

The unique properties of self-healing materials hold great potential in battery systems, which can exhibit excellent deformability and return to its original shape after cycling. Herein, a Cu3 BiS3 anode material with self-healing mechanisms is proposed for use in ultrastable potassium-ion battery (PIB) and potassium-ion hybrid capacitor (PIHC). Different from the binder design, Cu3 BiS3 anode can exhibit the dual advantages of phase and morphological reversibility, further remaining original property after potassiation/depotassiation and exhibiting ultrastable cycling performance. The reversible electrochemical reconstruction during the continuous charge/discharge processes is beneficial to maintain the structure and function of the material. Furthermore, the conversion reactions during the charge and discharge process produce two advantages: i) suppressing the shuttle effect due to the formation of the heterostructure interface between Cu (111) and Bi (012); ii) Cu can avoid the agglomeration of Bi nanoparticles (NPs), further improving the electrochemical performance and long-cycle stability of the Cu3 BiS3 electrode. As a result, the Cu3 BiS3 electrode not only exhibits a long cycle life in half cells, but also 2000 cycles and 12000 cycles in PIB and PIHC full cells, respectively.

Two dimensional MnPSe3 layer stacking composites with superior storage performance for alkali metal-ion batteries.

Two-dimensional MnPSe3 Van der Waals stacked in an ABC sequence has abundant and low-cost Mn resources, but has yet to exhibit expected performance as an electrode material in battery devices. Here, we report a 2D/2D composite consisting of few layer MnPSe3 nanosheets and graphite through a high energy ball milling method for uses on the anodes alkali metal-ion batteries, including lithium ion battery (LIB) and potassium ion battery (PIB). These unique 2D/2D layer nanostructures, with MnPSe3 layers hierarchically stacked in graphite, can successfully overcome the severe aggregation due to restacking during charge/discharge cycles. Moreover, density functional theory (DFT) calculations show that the band gap of the MnPSe3/graphite hybrid is as low as 0.07 eV, confirming that the combination of MnPSe3 and graphite efficiently reduces the ion migration energy barrier. As a result, MnPSe3/graphite stacking composites achieve a discharge capacity of 488.1 mA h g-1 after 500 cycles at 2000 mA g-1 in LIB, and 236.7 mA h g-1 after 700 cycles at 250 mA g-1 in PIB. Moreover, the analysis of electrochemical, kinetics, reactions mechanism, DFT, and full cell applications were investigated deeply. This work strongly supports the possibility of MnPSe3/graphite hybrid as a promising candidate for alkali ion batteries, and makes important improvements for the application of two-dimensional MPCh3 layer materials in storage systems.

Silver boosts ultra-long cycle life for metal sulfide lithium-ion battery anodes: Taking AgSbS2 nanowires as an example.

Metal sulfide, being a high-capacity anode material, is a promising anode material for rechargeable lithium-ion batteries (LIBs). However, most research efforts have focused on improving their low cycling performance due to multiple combined factors, including low conductivity, huge volume changes, multi-step conversion/alloying reactions, and redox shuttling effect, during the cycling process. Here, we report that by using AgSbS2 nanowires as LIB anode materials, a record-breaking long cycle life metal sulfide anode has been achieved through the silver synergistic electrochemical performance effect. We found that while the AgSbS2 nanowire anode is cycled, Ag precipitated out to form a nanocrystal tightly connected with Sb and S and plays a key role in highly-reversible electrochemical performance. Ag can effectively enhance the electrode conductivity, increase ion diffusion rate, serve a diluent huge volume changes during conversion-alloying reactions, improve the absorbability and catalytic ability towards LiPSs to reduce shutting effect of sulfur, and enhanced Li+ adsorption. As a result, AgSbS2 nanowire anodes maintain 90% capacity retention over 5000 and 7000 cycles at the current densities of 500 mA g-1 and 2000 mA g-1, respectively, whereas the capacities of Sb2S3 nanowire and Sb2S3/C nanowire anodes drop rapidly within 10 cycles. The ultra-stable cycle life is superior to the state-of-the-art metal sulfide anodes. Finally, using AgSbS2 nanowires as the anode combined with the cathode LiNi5Co3Mn2, a full battery after 480 cycles was assembled to verify that its stability (high retention rate of 99.5%) can be used in the current commercial battery architecture. This work solves multiple problems related to shuttling effects and complex reactions of metal sulfide anodes, and provides important progress for the future development of metal sulfide anodes for LIBs.

Recent Progress on Sb- and Bi-based Chalcogenide Anodes for Potassium-Ion Batteries.

Potassium ion batteries (PIBs) are potential alternative energy storage systems to lithium ion batteries (LIBs), due to elemental abundance of potassium, low cost and similar working principle to LIBs. Recently, metal chalcogenides (MCs) have gained enormous interests, especially antimony (Sb)-, bismuth (Bi)-based chalcogenides because they were able to undergo alloying/conversion dual mechanism, which can provide higher specific capacity and energy density (K3 Sb∼660 mA h g-1 , K3 Bi∼385 mA h g-1 ). However, several challenges hinder the development of Sb-, Bi-based chalcogenide anode materials for PIBs, such as huge volume expansion during potassiation, unstable solid-electrolyte interface (SEI), slow reaction kinetics, and polychalcogenide-induced shuttle effect. In this review, the current state-of-the-art Sb-, Bi-based chalcogenides are comprehensively summarized, including the reaction mechanism, electrochemical performance, ingenious nanostructures, electrolyte systems, and prospects for future development. This review contributes to understanding the K+ storage mechanism and the interaction between active materials and electrolytes, providing guidance and foundation for the design of next-generation high-performance PIBs.

Crystal Facet and Architecture Engineering of Metal Oxide Nanonetwork Anodes for High-Performance Potassium Ion Batteries and Hybrid Capacitors.

Metal oxides are considered as prospective dual-functional anode candidates for potassium ion batteries (PIBs) and hybrid capacitors (PIHCs) because of their abundance and high theoretic gravimetric capacity; however, due to the inherent insulating property of wide band gaps and deficient ion-transport kinetics, metal oxide anodes exhibit poor K+ electrochemical performance. In this work, we report crystal facet and architecture engineering of metal oxides to achieve significantly enhanced K+ storage performance. A bismuth antimonate (BiSbO4) nanonetwork with an architecture of perpendicularly crossed single crystal nanorods of majorly exposed (001) planes are synthesized via CTAB-mediated growth. (001) is found to be the preferential surface diffusion path for superior adsorption and K+ transport, and in addition, the interconnected nanorods gives rise to a robust matrix to enhance electrical conductivity and ion transport, as well as buffering dramatic volume change during insertion/extraction of K+. Thanks to the synergistic effect of facet and structural engineering of BiSbO4 electrodes, a stable dual conversion-alloying mechanism based on reversible six-electron transfer per formula unit of ternary metal oxides is realized, proceeding by reversible coexistence of potassium peroxide conversion reactions (KO2↔K2O) and BixSby alloying reactions (BiSb ↔ KBiSb ↔ K3BiSb). As a result, BiSbO4 nanonetwork anodes show outstanding potassium ion storage in terms of capacity, cycling life, and rate capability. Finally, the implementation of a BiSbO4 nanonetwork anode in the state-of-the-art full cell configuration of both PIBs and PIHCs shows satisfactory performance in a Ragone plot that sheds light on their practical applications for a wide range of K+-based energy storage devices. We believe this study will propose a promising avenue to design advanced hierarchical nanostructures of ternary or binary conversion-type materials for PIBs, PIHCs, or even for extensive energy storage.

Large-scale synthesis of few-layered copper antimony sulfide nanosheets as electrode materials for high-rate potassium-ion storage.

Metal chalcogenides (MCs) have received widespread attentions in potassium ion storage, due to their high theoretical specific capacity and low cost. However, practical applications are still a challenge because of the slow diffusion rate and large ionic radius, leading to dramatic volume expansion and slow rate performance. Herein, we introduce a simple and large scale solvothermal method to synthesize high-quality two-dimensional (2D) layered CuSbS2 nanosheets with a thickness of about 5 nm. The thin 2D layered structure has a weak van der Waals gap and a large exposed surface area to contact the electrolyte and promotes rapid K+ diffusion kinetics. In addition, the in-situ copper exsolution during potassiation process enhances the rate capability of K+ storage. CuSbS2 half cells exhibited excellent rate performance, delivering specific capacities of 573, 505, 476, 230, 177 mAh g-1 at current densities of 0.1, 0.5, 1, 5, 10 A g-1, respectively. The unique K+ electrochemical storage mechanism and resistance change during reaction process was revealed in detail by operando XRD, XPS and TEM. Finally, potassium ion hybrid capacitors (PIHCs) with CuSbS2 nanosheets as anode and AC as cathode demonstrated excellent performances with the maximum energy density of 127 W h kg-1 and the power density of 2415 W kg-1, providing an example of rationally design a high rate battery-type PIHC anode.

A carbon ink for use in thin, conductive, non peelable, amphiphilic, antioxidant, and large-area current collector coating with enhanced lithium ion battery performance.

We reported that a stable carbon ink composed of conductive carbon materials (graphene and super P), binder (sodium carboxymethyl cellulose (CMC)), interface active agent (sodium dodecyl sulfate (SDS)), and metal coupling agent ((3-aminopropyl)triethoxysilane (APTES)) for using in coating conducting layer on cathode/anode current collector for LIBs. Graphene materials are obtained using a low-cost graphite material (KS 6) and processing it via a wet ball-milling to exfoliate single layers into the ink. The ink can be coated on the LIB current collector in a large area by a doctor blade to form a carbon layer of about 1 µm without overflow. Carbon-coated current collectors have amphiphilic properties, not peel off under extreme physical and chemical conditions, and resist oxidation under high temperature (200 °C) processing conditions. In addition, carbon-coated current collector are superior to the batteries using bare metal foil a current collectors in the LIB performance of graphite half-cell, graphite full-cell, LiFePO4 half-cell, and silicon-carbon full-cell. These results show that the carbon-coated metal foil can reduce the interface resistance with the active material and improves the adhesion of the active materials to the current collector, avoiding peeling off during charge/discharge process, thereby improving of LIBs performance. The developed method can produce high-quality, low-cost carbon material inks on a large scale through a simple and inexpensive process, and coat them evenly and finely on current collectors, making it possible to achieve efficient industrial and commercial perspectives for next-generation LIB-based current collectors.

Synthesis of raspberry-like antimony-platinum (SbPt) nanoparticles as highly active electrocatalysts for hydrogen evolution reaction.

Binary transition metals can facilitate the hydrogen evolution reaction (HER) through the synergistic integration of different electrochemical properties. To determine binary transition metals that are highly active, Greely et al. conducted a simulation of 256 different binary transition metals. They demonstrated that BiPt, PtRu, AsPt, SbPt, BiRh, RhRe, PtRe, AsRu, IrRu, RhRu, IrRe, and PtRh could be used as efficient electrocatalysts for HER. However, only few of them are synthesized and used as electrocatalysts. In this work, we report the synthesis of the raspberry-like antimony-platinum (SbPt) nanoparticles (NPs) via a colloidal nanocrystal synthesis. These NPs exhibited efficient activity with a low overpotential of 27 mV to reach 10 mA cm-2 in acidic media. We conducted long-term durability test for 90,000 s under an applied voltage of 0.5 V (vs. RHE) and cycling tests of over 10,000 cycles under an applied voltage of 0.1 to -0.5 V (vs. RHE). The high activity exhibited by the raspberry-like SbPt NPs may be due to the following reasons: (1) the raspberry-like SbPt NPs exhibited versatile active exposed (110), (100), (101), and (012) facets as efficient HER catalysts, and (2) as confirmed by both the density functional theory (DFT) simulation and experimental results, the presence of Sb 3d subsurface broadened the Pt surface d-band, which caused synergistic effects on water splitting. In summary, synthesis of the new colloidal raspberry-like SbPt NPs is essential to elucidate the fundamental properties of the nanomaterial and nanostructure design. This study could facilitate the development of Pt-group materials that can be used as HER catalysts.

Bi-Sb Nanocrystals Embedded in Phosphorus as High-Performance Potassium Ion Battery Electrodes.

The development of high-performance potassium ion battery (KIB) electrodes requires a nanoengineering design aimed at optimizing the construction of active material/buffer material nanocomposites. These nanocomposites will alleviate the stress resulting from large volume changes induced by K+ ion insertion/extraction and enhance the electrical and ion conductivity. We report the synthesis of phosphorus-embedded ultrasmall bismuth-antimony nanocrystals (BixSb1-x@P, (0 ≤ x ≤ 1)) for KIB anodes via a facile solution precipitation at room temperature. BixSb1-x@P nanocomposites can enhance potassiation-depotassiation reactions with K+ ions, owing to several attributes. First, by adjusting the feed ratios of the Bi/Sb reactants, the composition of BixSb1-x nanocrystals can be systematically tuned for the best KIB anode performance. Second, extremely small (diameter ≈ 3 nm) BixSb1-x nanocrystals were obtained after cycling and were fixed firmly inside the P matrix. These nanocrystals were effective in buffering the large volume change and preventing the collapse of the electrode. Third, the P matrix served as a good medium for both electron and K+ ion transport to enable rapid charge and discharge processes. Fourth, thin and stable solid electrolyte interface (SEI) layers that formed on the surface of the cycled BixSb1-x@P electrodes resulted in low resistance of the overall battery electrode. Lastly, in situ X-ray diffraction analysis of K+ ion insertion/extraction into/from the BixSb1-x@P electrodes revealed that the potassium storage mechanism involves a simple, direct, and reversible reaction pathway: (Bi, Sb) ↔ K(Bi, Sb) ↔ K3(Bi, Sb). Therefore, electrodes with the optimized composition, i.e., Bi0.5Sb0.5@P, exhibited excellent electrochemical performance (in terms of specific capacity, rate capacities, and cycling stability) as KIB anodes. Bi0.5Sb0.5@P anodes retained specific capacities of 295.4 mA h g-1 at 500 mA g-1 and 339.1 mA h g-1 at 1 A g-1 after 800 and 550 cycles, respectively. Furthermore, a capacity of 258.5 mA h g-1 even at 6.5 A g-1 revealed the outstanding rate capability of the Sb-based KIB anodes. Proof-of-concept KIBs utilizing Bi0.5Sb0.5@P as an anode and PTCDA (perylenetetracarboxylic dianhydride) as a cathode were used to demonstrate the applicability of Bi0.5Sb0.5@P electrodes to full cells. This study shows that BixSb1-x@P nanocomposites are promising carbon-free anode materials for KIB anodes and are readily compatible with the commercial slurry-coating process applied in the battery manufacturing industry.

Correction: Colloidal synthesis of porous red phosphorus nanoparticles as a metal-free electrocatalyst for the hydrogen evolution reaction.

Correction for 'Colloidal synthesis of porous red phosphorus nanoparticles as a metal-free electrocatalyst for the hydrogen evolution reaction' by Cheng-Ying Chan et al., Chem. Commun., 2020, 56, 2937-2940, DOI: .

Colloidal synthesis of porous red phosphorus nanoparticles as a metal-free electrocatalyst for the hydrogen evolution reaction.

Porous red phosphorus nanoparticles, P-RPNPs, were synthesized via a new colloidal approach and used as metal-free electrocatalysts in the hydrogen evolution reaction (HER). P-RPNPs were highly efficient in acidic media, required an overpotential of only 218 mV to reach 10 mA cm-2, and exhibited superior long-term durability.

Red Phosphorus Potassium-Ion Battery Anodes.

Phosphorus (P) possesses the highest theoretical specific capacity (865 mA h g-1) among all the elements for potassium-ion battery (PIB) anodes. Although Red P (RP) has intrinsic advantages over its allotropes, including low cost and nontoxicity, and simpler preparation, it is yet unknown to effectively activate it into a high-performance PIB anode. Here, high-performance RP PIB anodes are reported. Two important factors are found to facilitate RP react with K-ions reversibly: i) nanoscale RP particles are dispersed evenly in a conductive carbon matrix composed of multiwall carbon nanotubes and Ketjen black that provide an efficient electrical pathway and a tough scaffold. ii) The results of X-ray photoelectron spectroscopy spectrum and the electrochemical performance perhaps show that no P-C bond formation is beneficial to allow K-ions to react with RP effectively. As a result, the RP/C electrodes deliver a reversible specific capacity of ≈750 mA h g-1 and exhibit a high-rate capability (≈300 mA h g-1 at 1000 mA g-1). RP/C full cells using potassium manganese hexacyanoferrate as cathode show a long cycling life (680 cycles) at a current density of 1000 mA g-1, in addition, a pouch-type battery is built to demonstrate practical applications.

The shape-controlled synthesis of gallium-palladium (GaPd2) nanomaterials as high-performance electrocatalysts for the hydrogen evolution reaction.

Recently, great efforts have been focused on developing more active and stable Pd-based electrocatalysts to partially or completely replace rare and costly Pt. We developed a facile hot injection method and successfully synthesized well-dispersed and shape-controlled GaPd2 nanomaterials including polyhedrons, nanoparticles and nanowires. All the as-synthesized catalysts exhibit superior HER activity compared to commercial pure Pd catalysts and are stable in acidic media. Among them, the GaPd2 nanoparticles required only 24.3 mV overpotential to achieve a 10 mA cm-2 current density, which is outstanding compared to most Pt-based nanomaterials. Also, cycling tests over 10 000 CV sweep cycles (-0.3 to 0.2 vs. RHE) and durability testing for 24 hours were applied, with the GaPd2 catalysts exhibiting similar i-V curves and stable current densities to those obtained in the initial tests. We further evaluated the mass activities of the GaPd2 catalysts, and it is fascinating that the GaPd2 polyhedrons, nanoparticles and nanowires achieved factors of 3.7, 5 and 2.3 enhancement in mass activity at -0.1 V vs. RHE compared with a commercial Pd black catalyst. Meanwhile, with the assistance of a reduced graphene oxide (rGO) support, the GaPd2 nanoparticles/rGO (20 wt%) electrocatalyst presents outstanding HER activity comparable with that of a carbon-supported Pt catalyst (20% Pt/C). This work provides an avenue to develop effective and stable Pd-based catalysts with reduced Pd usage and high HER performance.

Sub-1 nm PtSn ultrathin sheet as an extraordinary electrocatalyst for methanol and ethanol oxidation reactions.

Sub-1 nm PtSn nanosheets of 0.6-0.9 nm in thickness were synthesized via a solution colloidal method and were applied as electrooxidation catalysts for methanol oxidation reaction (MOR) and ethanol oxidation (EOR) in alkaline and acid environments. Owing to the specific structural and compositional characteristics, the as-prepared PtSn nanosheets exhibits superior activity and durability relative to commercial Pt black and Pt/carbon catalysts. PtSn nanosheets not only exhibit an outstanding mass activity in MOR (871.6 mA mg Pt-1), which is 2.3 times (371 mA mg Pt-1) and 10.1 times (86.1 mA mg Pt-1) higher than that of commercial Pt/carbon and Pt black respectively, but also display an mass activity in EOR (673.6 mA mg Pt-1) with 5.3 times higher commercial Pt black (127.7 mA mg Pt-1) and 2.3 times higher than commercial Pt/C catalyst (295 mA mgPt-1). The reported value is the highest activity in both MOR and EOR examinations compared to the reported PtSn-based electrocatalysts,. The improved performance may be due to the highly-reactive exposed (1 1 1) facet sites resulted from its sub-1 nm 2D sheet like morphology.

Monodisperse ordered indium-palladium nanoparticles: synthesis and role of indium for boosting superior electrocatalytic activity for ethanol oxidation reaction.

The slow kinetics of ethanol oxidation reaction (EOR) has limited its widespread use for fuel cells. Bimetallic catalysts with optimized surface compositions can considerably govern rate-determining steps through selectivity for CH3COOH formation or by facilitating the adsorption of OHadsvia the bifunctional effect of an alloy to increase the EOR's kinetic rates. Here, we reported monodisperse ordered In-Pd nanoparticles as new bimetallic high-performance catalysts for EOR. In-Pd nanoparticles, i.e., In3Pd2 and In3Pd5 were prepared using arrested precipitation in solution, and their composition, structures, phase and crystallinity were confirmed using a variety of analyses including TEM, XPS, EDS and XRD. In-Pd nanoparticles were loaded on carbon black (Vulcan XC-72) as electrocatalysts for EOR in alkaline media. In3Pd2 and In3Pd5 nanoparticles exhibited 5.8 times and 4.0 times higher mass activities than commercial Pd/C, which showed that the presence of indium greatly boosts electrocatalytic reactivity for EOR of Pd catalysts. This performance is the best among those of bimetallic nanoparticles reported to date. Such high performance of In-Pd nanoparticles may be attributed to the following two reasons. First, In-Pd nanoparticles exhibited excellent CO anti-poison ability, as confirmed by CO striping experiments. Second, as revealed by DFT calculations of metals with OHads adsorption, In atoms on In3Pd2 surface exhibited the lowest energy (-1.659 eV) for OHads adsorption as compared to other common oxophilic metals including Sn, SnPt, Ag, Ge, Co, Pb, and Cu. We propose that the presence of indium sites promoted efficient free OH radical adsorption on indium sites and resulted in a faster reaction rate of acetate formation from acetaldehyde (the rate determining step for EOR on Pd sites). Finally, a single direct ethanol fuel cell (DEFC) with Pd/C anode was prepared. Compared to the results for a commercial Pd/C anode, the open circuit voltage (OCV) of In3Pd2/C improved by 0.25 V (from 0.64 to 0.89 V) and the power density improved by ∼80% (from 3.7 to 6.7 mW cm-2), demonstrating its practical uses as Pt or Pd catalyst alternatives for DEFC.

Synthesis of germanium-platinum nanoparticles as high-performance catalysts for spray-deposited large-area dye-sensitized solar cells (DSSC) and the hydrogen evolution reaction (HER).

GePt3 and Ge2Pt nanoparticles were synthesized via a solution colloidal method as catalysts for dye-sensitized solar cells (DSSC) and the hydrogen evolution reaction (HER). The shape, size, arrangement, phases and crystalline structures of Ge-Pt nanoparticles were determined, and the ability to be dispersed in nonpolar solvents enabled them to form a catalyst ink with a stable ejection for the spray coating technique. A series of electrochemical analyses confirmed the catalytic properties of Ge-Pt nanoparticles toward the I-/I3- redox reaction system. The DSSC using GePt3 nanoparticles as the counter electrode exhibited excellent power conversion efficiency (PCE) of 8.04% at 0.16 cm2, which was comparable to that of a DSSC using Pt as the counter electrode (8.0%); it also exhibited an average PCE of 7.26% even at a large working area (2 cm2). In addition, the GePt3 catalyst exhibited excellent HER electrocatalytic performance with a large current density and a low Tafel slope, and it could stably operate at a working area of up to 5 cm2 with a low over potential (<0.06 V) to achieve 10 mA cm-2 cathodic current. This study provides fundamental insights into the preparation of germanium-platinum intermetallic compound catalysts at the nanoscale, which can be beneficial for the design and development of clean energy devices.