Nanostructure Optimization of Platinum-Based Nanomaterials for Catalytic Applications.

Platinum-based nanomaterials have attracted much interest for their promising potentials in fields of energy-related and environmental catalysis. Designing and controlling the surface/interface structure of platinum-based nanomaterials at the atomic scale and understanding the structure-property relationship have great significance for optimizing the performances in practical catalytic applications. In this review, the strategies to obtain platinum-based catalysts with fantastic activity and great stability by composition regulation, shape control, three-dimension structure construction, and anchoring onto supports, are presented in detail. Moreover, the structure-property relationship of platinum-based nanomaterials are also exhibited, and a brief outlook are given on the challenges and possible solutions in future development of platinum-based nanomaterials towards catalytic reactions.

Morphology-Controlled Synthesis of Hematite Nanocrystals and Their Optical, Magnetic and Electrochemical Performance.

A series of α-Fe2O3 nanocrystals (NCs) with fascinating morphologies, such as hollow nanoolives, nanotubes, nanospindles, and nanoplates, were prepared through a simple template-free hydrothermal synthesis process. The results showed that the morphologies could be easily controlled by SO42- and H2PO4-. Physical property analysis showed that the α-Fe2O3 NCs exhibited shape- and size-dependent ferromagnetic and optical behaviors. The absorption band peak of the α-Fe2O3 NCs could be tuned from 320 to 610 nm. Furthermore, when applied as electrode material for supercapacitor, the hollow olive-structure exhibited the highest capacitance (285.9 F·g-1) and an excellent long-term cycling stability (93% after 3000 cycles), indicating that it could serve as a candidate electrode material for a supercapacitor.

Porous Pt-NiO x nanostructures with ultrasmall building blocks and enhanced electrocatalytic activity for the ethanol oxidation reaction.

Oxidized species on surfaces would significantly improve the electrocatalytic activity of Pt-based materials. Constructing three-dimensional porous structures would endow the catalysts with good stability. Here, we report a simple strategy to synthesize porous Pt-NiO x nanostructures composed of ultrasmall (about 3.0 nm) building blocks in an ethanol-water solvent. Structure and component analysis revealed that the as-prepared material consisted of interconnected Pt nanocrystals and amorphous NiO x species. The formation mechanism investigation revealed that the preformed amorphous compounds were vital for the construction of porous structure. In the ethanol oxidation reaction, Pt-NiO x /C exhibited current densities of 0.50 mA cmPt -2 at 0.45 V (vs. SCE), which were 16.7 times higher than that of a commercial Pt/C catalyst. Potentiostatic tests showed that Pt-NiO x /C had much higher current and better tolerance towards CO poisoning than the Pt/C catalyst under 0.45 V (vs. SCE). In addition, the NiO x species on the surface also outperformed an alloyed Ni component in the test. These results indicate that the Pt-NiO x porous nanomaterial is promising for use in direct ethanol fuel cells.

Hollow Co2P nanoflowers assembled from nanorods for ultralong cycle-life supercapacitors.

Hollow Co2P nanoflowers (Co2P HNFs) were successfully prepared via a one-step, template-free method. Microstructure analysis reveals that Co2P HNFs are assembled from nanorods and possess abundant mesopores and an amorphous carbon shell. Density functional theory calculations and electrochemical measurements demonstrate the high electrical conductivity of Co2P. Benefiting from the unique nanostructures, when employed as an electrode material for supercapacitors, Co2P HNFs exhibit a high specific capacitance, an outstanding rate capability, and an ultralong cycling stability. Furthermore, the constructed Co2P HNF//AC ASC exhibits a high energy density of 30.5 W h kg-1 at a power density of 850 W kg-1, along with a superior cycling performance (108.0% specific capacitance retained after 10 000 cycles at 5 A g-1). These impressive results make Co2P HNFs a promising candidate for supercapacitor applications.

Interconnected hierarchical NiCo2O4 microspheres as high-performance electrode materials for supercapacitors.

Herein, interconnected hierarchical NiCo2O4 microspheres (IH-NiCo2O4) were prepared via a solvothermal method followed by an annealing treatment. IH-NiCo2O4 possesses large tunnels and abundant mesopores, which are in favor of their applications in energy storage field. When employed as an electrode material for supercapacitors, IH-NiCo2O4 exhibits a high specific capacitance of 1822.3 F g-1 at a current density of 2 A g-1, an excellent rate property of 68.6% capacity retention at 20 A g-1, and an 87.6% specific capacitance retention of its initial value after 7000 cycles at a high current density of 10 A g-1, superior to those of IH-Co3O4. Furthermore, an optimal asymmetric supercapacitor (ASC) was also constructed with IH-NiCo2O4 as the positive electrode and graphene as the negative electrode. The ASC delivers a high energy density of 39.4 Wh kg-1 at a power density of 800 W kg-1. Even at a high power density of 8000 W kg-1, the energy density still reaches 27.2 Wh kg-1. Moreover, the ASC shows a good cycling stability with 80.1% specific capacitance retention after 5000 cycles at 6 A g-1. The excellent electrochemical performance of IH-NiCo2O4 makes it a promising electrode material in energy storage field.