Carbon dioxide (CO2) hydrogenation to ethanol (C2H5OH) is considered a promising way for CO2 conversion and utilization, whereas desirable conversion efficiency remains a challenge. Herein, highly active, selective and stable CO2 hydrogenation to C2H5OH was enabled by highly ordered Pd-Cu nanoparticles (NPs). By tuning the composition of the Pd-Cu NPs and catalyst supports, the efficiency of CO2 hydrogenation to C2H5OH was well optimized with Pd2Cu NPs/P25 exhibiting high selectivity to C2H5OH of up to 92.0% and the highest turnover frequency of 359.0 h–1. Diffuse reflectance infrared Fourier transform spectroscopy results revealed the high C2H5OH production and selectivity of Pd2Cu NPs/P25 can be ascribed to boosting *CO (adsorption CO) hydrogenation to *HCO, the rate-determining step for the CO2 hydrogenation to C2H5OH.

The structures of the noble metal nanocrystals (NCs) deeply impact their catalytic properties, and therefore, it is imperative to explore feasible routes for controllable synthesis. Despite promising performances of Rh NCs in various applications, the systematical shape control of Rh NCs is still a formidable challenge due to its high surface energy. Herein, we demonstrate a route to realize the systematically controlled synthesis of Rh NCs from tetrahedron (TH), to concave tetrahedron (CT), and to nanosheet (NS) by simply switching the volume ratios between oleylamine (OAm) to 1-octadecene (ODE). This series of Rh NCs provides an ideal platform to carry out structure-dependent catalytic investigations in hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Significantly, all the Rh NCs exhibit highly efficient HER and OER activities, as well as outstanding stabilities during long-term durability tests with Rh NSs being the best, showing a class of promising catalysts for water splitting. This present study demonstrates the first example in investigating the solvent effects on modulating the structures of Rh NCs that promises huge opportunities for optimizing the electrochemical catalysis.

Although explosive studies on pursuing high-performance Pt-based nanomaterials for fuel cell reactions have been carried out, the combined controls of surface composition, exposed facet, and interior structure of the catalyst remains a formidable challenge. We demonstrate herein a facile chemical approach to realize a new class of intermetallic Pt–Pb–Ni octahedra for the first time. Those nanostructures with unique intermetallic core, active surface composition, and the exposed facet enhance oxygen reduction electrocatalysis with the optimized PtPb1.12Ni0.14 octahedra exhibiting superior specific and mass activities (5.16 mA/cm2 and 1.92 A/mgPt) for oxygen reduction reaction (ORR) that are ∼20 and ∼11 times higher than the commercial Pt/C, respectively. Moreover, the PtPb1.12Ni0.14 octahedra can endure at least 15 000 cycles with negligible activity decay, showing a new class of Pt-based electrocatalysts with enhanced performance for fuel cells and beyond.

Among various platinum (Pt)-based nanostructures, porous or hollow ones are of great importance because they exhibit fantastic oxygen reduction reaction (ORR) enhancements and maximize atomic utilization by exposing both exterior and interior surfaces. Here, a new class of porous Pt3Ni nanowires (NWs) with 1D architecture, an ultrathin Pt-rich shell, high index facets, and a highly open structure is designed via a selective etching strategy by using the phase and composition segregated Pt-Ni NWs as the starting material. The porous feature of Pt3Ni NWs can be readily fulfilled by changing the Pt/Ni atomic ratio of the starting Pt-Ni NWs. Such porous Pt3Ni NWs show extraordinary activity and stability enhancements toward methanol oxidation reaction and ORR. The porous Pt3Ni NWs can deliver ORR mass activity of 5.60 A mg−1, which is 37.3-fold higher than that of the Pt/C. They also show outstanding stability with negligible activity loss after 20 000 cycles. This study offers a unique approach for the design of complex nanostructures as efficient catalysts through precisely tailoring.

Direct alcohol fuel cells (DAFCs) have attracted growing research interest as clean high-efficiency energy conversion devices, however the design and creation of high-performance anode catalysts for DAFCs is still extremely desirable. Herein, we report a wet-chemical method for making bimetallic aerogel networked Pt–Sn nanowires (NWs) with tunable compositions. All of the obtained networked Pt–Sn NWs exhibit better mass activities and specific activities in both the methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) than commercial Pt/C due to their unique three-dimensional (3D) porosity with larger surface areas and the presence of structural defects, with the optimized networked Pt6Sn3 NWs displaying the best mass activities of up to 1.08 mA μgPt−1 for the EOR and 1.45 mA μgPt−1 for the MOR in acid media. The networked Pt6Sn3 NWs also exhibited enhanced stability toward both the EOR and MOR compared to Pt/C. The present work suggests that the networked NWs with high surface areas and rich defects are indeed a unique class of efficient electrocatalysts for alcohol electrooxidation.

Platinum (Pt) is the best catalyst component towards fuel cell reactions, while its scarcity and high cost largely restrict its practical applications. To overcome these limitations, precisely designing functional Pt-based electrocatalysts is highly desirable. Herein, for the first time we report a facile strategy for the construction of ternary PtNi/PtxPb/Pt core/multishell nanowires (NWs), which combine the features of a core–multishell structure, an alloy effect, and a one dimensional structure. The use of preformed ultrathin PtNi NWs as substrates, sequential reduction/diffusion of Pb onto the ultrathin PtNi NWs, and the further reduction of Pt play important roles in the formation of ternary PtNi/PtxPb/Pt NWs. The combined features enable them to be more active and stable for anodic alcohol oxidations including the methanol oxidation reaction, ethanol oxidation reaction, ethylene glycol oxidation reaction, and glycerol oxidation reaction, as well as the cathodic oxygen reduction reaction than commercial Pt/C. Among various electrocatalysts investigated, the optimized PtNi0.67Pb0.26 NWs show the best activity and durability for all the fuel cell reactions tested. This work highlights the importance of precise composition and structure tunings of Pt-based electrocatalysts for fuel cell reactions.

Electrochemically splitting water into hydrogen (H2) and oxygen (O2) is a promising method for clean energy generation, while the absence of highly active, stable, low-cost and earth abundant catalysts greatly impedes its large-scale application. Herein, we report a general and robust approach for the controlled synthesis of a class of NiM (M = Fe, Co, Mn) hydroxide nanosheets (HNSs) that have ultrathin thicknesses of around 2 nm. Such unique structures enable the HNSs to have promising oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performances, with the NiFe HNSs being the best candidate. Given the well-defined electrochemical bifunctionality, a full alkaline electrolyzer was constructed using NiFe HNSs as both the cathodic and the anodic catalysts. It can realize overall water splitting with a current density of 10 mA cm−2 at 1.67 V and has remarkable durability for 12 h. This work opens a new avenue to approach water splitting catalysis using efficient low-cost Ni-based HNSs.

Shape-controlled noble metal nanocrystals (NCs), such as Au, Ag, Pt, Pd, Ru, and Rh are of great success due to their new and enhanced properties and applications in chemical conversion, fuel cells, and sensors, but the realization of shape control of Ir NCs for achieving enhanced electrocatalysis remains a significant challenge. Herein, we report an efficient solution method for a new class of three-dimensional (3D) Ir superstructure that consists of ultrathin Ir nanosheets as subunits. Electrochemical studies show that it delivers the excellent electrocatalytic activity toward oxygen evolution reaction (OER) in alkaline condition with an onset potential at 1.43 V versus reversible hydrogen electrode (RHE) and a very low Tafel slope of 32.7 mV decade–1. In particular, it even shows superior performance for OER in acidic solutions with the low onset overpotential of 1.45 V versus RHE and small Tafel slope of 40.8 mV decade–1, which are much better than those of small Ir nanoparticles (NPs). The 3D Ir superstructures also exhibit good stability under acidic condition with the potential shift of less than 20 mV after 8 h i-t test. The present work highlights the importance of tuning 3D structures of Ir NCs for enhancing OER performance.

Highly open metallic nanoframes represent an emerging class of new nanostructures for advanced catalytic applications due to their fancy outline and largely increased accessible surface area. However, to date, the creation of bimetallic nanoframes with tunable structure remains a challenge. Herein, we develop a simple yet efficient chemical method that allows the preparation of highly composition segregated Pt–Ni nanocrystals with controllable shape and high yield. The selective use of dodecyltrimethylammonium chloride (DTAC) and control of oleylamine (OM)/oleic acid (OA) ratio are critical to the controllable creation of highly composition segregated Pt–Ni nanocrystals. While DTAC mediates the compositional anisotropic growth, the OM/OA ratio controls the shapes of the obtained highly composition segregated Pt–Ni nanocrystals. To the best of our knowledge, this is the first report on composition segregated tetrahexahedral Pt–Ni NCs. Importantly, by simply treating the highly composition segregated Pt–Ni nanocrystals with acetic acid overnight, those solid Pt–Ni nanocrystals can be readily transformed into highly open Pt–Ni nanoframes with hardly changed shape and size. The resulting highly open Pt–Ni nanoframes are high-performance electrocatalysts for both oxygen reduction reaction and alcohol oxidations, which are far better than those of commercial Pt/C catalyst. Our results reported herein suggest that enhanced catalysts can be developed by engineering the structure/composition of the nanocrystals.

Introducing high-index facets into nanocrystals (NCs) is an effective way for boosting the electrocatalytic intrinsic activity. However, the established NCs with high-index facets usually have a big diameter, which makes them exhibit a very limited surface area, thus finally limited mass activity. To embody the advantage of high-index facets in enhancing electrocatalysis well, the better nanostructures should meet the requirement of both high surface area and high-density high-index facets. Herein, we report our important advances in making the unique three-dimensional screw thread-like platinum–copper (Pt–Cu) alloy nanowires (NWs) with high-density high-index facets and controlled composition. Such special NWs with a high surface area of 46.90 m2 g–1 exhibit much better performance than the PtCu nanoparticles (NPs) in alcohol electrooxidations. This work opens a new way for maximizing the electrocatalytic performance by introducing high-index facets into high-surface-area stable bimetallic NWs.Keywords: copper; liquid fuels oxidation; nanowires; Platinum; screw thread-like;

The layered molybdenum disulfide (MoS2) nanostructured materials are of great interest for electrochemical energy storage and conversion and electrocatalytic water splitting. However, they still exhibit very limited performance because of their limited active sites. To create more efficient MoS2 materials, herein, we develop a simple yet efficient approach to a unique column-like MoS2 superstructure composed of edge-terminated MoS2 nanosheets (CLET MoS2). These MoS2 nanosheets as building blocks with fully exposed active edges are oriented in a preferred manner, rendering CLET MoS2 that exhibits excellent electrochemical performance in both lithium ion storage and hydrogen evolution reaction (HER). Compared with that of commercial MoS2, these hierarchical MoS2 superstructures possess much higher specific capacity and superior cycling performance for lithium ion storage and excellent electrocatalytic activity and stability for HER with a very low Tafel slope of 39 mV decade–1, showing their great potential applications in lithium ion batteries and water splitting.

The development of highly efficient fuel cell devices is largely impeded by the limited electrocatalytic activity and stability of available Pt-based electrocatalysts. Herein, we report a facile one-pot strategy for the controlled synthesis of hierarchical Pt/PtxPb core/shell nanowires (NWs) with dendritic morphology. Different from the reported NWs, the present hierarchical core/shell NWs show the integrated features of one-dimensional (1D) structure, core/shell structure, alloy effect, and high surface area. These important characteristics enable them to be much more active and stable for methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) than Pt NWs, the Pt-Pb nanoparticles (NPs), and commercial Pt/C (20 wt %, Pt particle size: 2–5 nm, Johnson Matthey) catalyst. Particularly, the present PtPb0.27 NWs are very stable in the MOR and EOR conditions with much lower activity decay after 1000 potential cycles than those of Pt-Pb NPs and the commercial Pt/C. This work highlights the importance of the precise control over 3D hierarchical structure in enhancing electrocatalysis for liquid fuel oxidations.

Pd has been considered as the possible economical substitute of rare Pt for catalyzing the liquid fuels electrooxidation reaction. However, the biggest problem of Pd nanocatalysts for alcohol oxidations is that they show the limited stability and activity, greatly impacting the development of liquid fuels-based fuel cell technology. We report herein a new solvent-induced procedure for making distinct Pd NCs with geometry tuning from Pd nanosheets, Pd tetrapods, to Pd concave tetrahedra by switching the solvent from 1-methyl-2-pyrrolidone, formamide, to acetylacetonate. The key features for the preparation of dimension-controlled Pd NCs herein are that the use of molybdenum carbonyl (Mo(CO)6) determines the exposed {111} facet in the final Pd NCs, while different solvents control the reduction kinetics to induce the growth of Pd NCs with distinct morphologies. The as-prepared distinct Pd NCs show the interesting shape-dependent electrocatalytic activities toward multiple liquid fuels electrooxidation reactions including ethylene glycol oxidation reaction, glycerol oxidation reaction, ethanol oxidation reaction, and also methanol oxidation reaction with Pd nanosheets exhibiting higher activity than all the other Pd catalysts and higher activity than the commercial Pd/C and also Pd black due to the thin character of Pd nanosheets. Most importantly, the Pd nanosheets exhibit much higher stability for multiple liquid fuels electrooxidation than all the other Pd catalysts tested. The present work gives the first example in exploring the effect of solvent in tuning the dimensions of Pd NCs, and thus optimizing the electrocatalytic performance for liquid fuels electrooxidation.Keywords: catalysis; liquid fuels; nanosheets; palladium; shape control

Despite the great success that has been accomplished on the controlled synthesis of Pd nanocrystals with various sizes and morphologies, an efficient approach to systematic production of well-defined Pd nanocrystals without seed-mediated approaches remains a significant challenge. In this work, we have developed an efficient synthetic method to directly produce Pd nanocrystals with a highly controllable feature. Three distinct Pd nanocrystals, namely, Pd nanosheets, Pd concave tetrahedra, and Pd tetrahedra, have been selectively prepared by simply introducing a small amount of ascorbic acid (AA) and/or water without the other synthesis conditions changed. We found that the combined use of AA and water is of importance for the successful production of the unique Pd nanosheets. Detailed catalytic investigations showed that all the obtained Pd nanocrystals exhibit higher activity in the formic acid electrooxidation and styrene hydrogenation with respect to the Pd black, and their activities are highly shape-dependent with Pd nanosheets demonstrating a higher activity than both the Pd concave tetrahedra and Pd tetrahedra, which is likely due to the simple yet important feature of ultrathin thickness of Pd nanosheets. The present work highlights the importance of structures in tuning the related properties of metallic nanocrystals.

Herein, we report a facile strategy that allows one-pot preparation of highly open rhombic dodecahedral PtCu alloy nanoframes. Due to the highly open structures, the PtCu nanoframes exhibit enhanced catalytic performance in methanol electrooxidation, showing a new strategy to create highly active catalysts.

An efficient synthetic approach that enables not only the control of Pt nanocubes but also the one-pot fabrication of novel Pt nanocube assemblies was developed for the first time. The integration of well-defined building blocks and unique superstructures endows Pt nanocube assemblies with enhanced performance in the methanol electrooxidation, showing a new concept for further enhancing the performance of these catalysts.

The design and creation of efficient catalysts for alcohol oxidation reaction has attracted great research attention because alcohols are promising fuels for direct fuel cell reactions because of their high energy density, easy storage, and transportation. We herein report an efficient strategy that allows the preparation of ternary PtSnM (M = Co, Ni, and Rh) wavy nanowires (WNWs) with ultrathin diameter of only around 2 nm and tunable compositions in high yield. Detailed catalytic studies show that all the ternary WNWs exhibit high performance for ethanol oxidation reaction (EOR) and methanol oxidation reaction (MOR), and their performance shows interesting composition-dependent electrocatalytic activity with PtSnRh WNWs having the best activity for both EOR and MOR. The PtSnRh WNWs are also more stable than commercial Pt/C catalyst, as revealed by long-time chronoamperometric (CA) measurements. The present work highlights the use of multimetallic WNWs as highly active and durable nanocatalysts in enhancing alcohol electrooxidation, which will open a new way in tuning 1D multimetallic nanostructures for boosting other fuel cell reactions, various heterogeneous reactions, and beyond.Keywords: alcohol electrooxidation; platinum; rhodium; tin; wavy nanowires;

Despite that different facets have distinct catalytic behavior, the important role of twin defects on enhancing the catalytic performance of metallic nanocrystals is largely unrevealed. The key challenge in demonstrating the importance of twin defects for catalysis is the extreme difficulties in creating nanostructures with the same exposed facets but tunable twin defects that are suitable for catalytic investigations. Herein, we show an efficient synthetic strategy to selectively synthesize {111}-terminated Pt3Cu nanocrystals with controllable crystalline features. Two distinct {111}-bounded shapes, namely, multiply-twinned Pt3Cu icosahedra and single-crystalline Pt3Cu octahedra, are successfully prepared by simply changing the types of Cu precursors with the other growth parameters unchanged. Electrocatalytic studies show that the {111}-terminated Pt3Cu nanocrystals exhibit the very interesting crystalline nature-dependent electrocatalytic activities toward both the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) with multiply-twinned Pt3Cu icosahedra demonstrating enhanced electrocatalytic activities compared to the single-crystalline Pt3Cu octahedra due to their additional yet important effect of twin defect. As a result, under the multiple tuning conditions (alloy, shape, and twin effects), the multiply-twinned Pt3Cu icosahedra exhibit much enhanced electrocatalytic activities in both ORR and MOR with respect to the Pt black. The present work highlights the importance of twin defects in enhancing electrocatalytic activities of metallic nanocrystals.Keywords: copper; electrocatalyst; icosahedron; Platinum; twin defect;

Herein, we report a facile strategy that allows one-pot preparation of highly open rhombic dodecahedral PtCu alloy nanoframes. Due to the highly open structures, the PtCu nanoframes exhibit enhanced catalytic performance in methanol electrooxidation, showing a new strategy to create highly active catalysts.

Electrochemically splitting water into hydrogen (H2) and oxygen (O2) is a promising method for clean energy generation, while the absence of highly active, stable, low-cost and earth abundant catalysts greatly impedes its large-scale application. Herein, we report a general and robust approach for the controlled synthesis of a class of NiM (M = Fe, Co, Mn) hydroxide nanosheets (HNSs) that have ultrathin thicknesses of around 2 nm. Such unique structures enable the HNSs to have promising oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performances, with the NiFe HNSs being the best candidate. Given the well-defined electrochemical bifunctionality, a full alkaline electrolyzer was constructed using NiFe HNSs as both the cathodic and the anodic catalysts. It can realize overall water splitting with a current density of 10 mA cm−2 at 1.67 V and has remarkable durability for 12 h. This work opens a new avenue to approach water splitting catalysis using efficient low-cost Ni-based HNSs.

An efficient synthetic approach that enables not only the control of Pt nanocubes but also the one-pot fabrication of novel Pt nanocube assemblies was developed for the first time. The integration of well-defined building blocks and unique superstructures endows Pt nanocube assemblies with enhanced performance in the methanol electrooxidation, showing a new concept for further enhancing the performance of these catalysts.