Characteristic examples of three types of change of form of p n relationships at 2 5 T , as the contents of elements alloying with palladium a r e gradually increased (4,37,70,74-83,95-98,~04,108,153,154), are illustrated in Figure 9. As for the palladiumhydrogen system itself (4), such relationships have been determined from direct equilibrations with hydrogen gas, as well as being derived from measurements of electrode potential. Similarly as for palladium-hydrogen, temperature dependences of the p n relationships have been used to supplement calorimetric data ( I 10) in deriving heats and cntropies of hydrogen absorption, both at initially low values (79)(80)(81)(82)95,100,108) of hydrogen content (n-to) and over (Y =p transition regionsThe sequence of relationships in Figure 9(c) (4,37,70,74-83,'04,I54,I78).shows gradual increases with increasing rhodium content in the range o f n over which (Y and / J ' phases coexist. This sequence now seems unique to the palladium-rhodium-hydrogen system (45,75, I 53,154), since some suggestions of similarities of the palladium-manganesehydrogen system (179) seem doubtful in view of possible incomplete equilibrations.'The remaining families of p n isotherms for palladium alloy-hydrogen systems would thus seem to be divisible into two groups represented by those in Figures 9(a) and 9 (b). In both cases the ranges of n over t i + p phase regions are successively shortened with increasing content of the alloying element, even in the cases of alloys with readily hydride-forming transition or inner transition elements such as vanadium Decreases, in the range of n over (r +/I regions, with increasing amounts of alloying elements, have continued to be deduced from X-ray determinations of and / 3 phase lattice constants for additional palladium alloyhydrogen systems (4,79-82,157, I 80-1 82).Apart from the probable case of the palladium-nickel-hydrogen system (so), these general trends of decreasing extents of ( Y , p coexistence with increasing contents of alloying element are similar to the effects of increasing temperature in the palladium-hydrogen system, being accompanied by decreases in the extents of hystereses of absorption and desorption relationships between hydrogen contents and other experimental parameters (4,69,(96)(97)(98) later, has importance in choices of alloy compositions as hydrogen permeation membranes. In addition to the arguments concerning the solubility of hydrogen in the palladium-silver alloys, the extents of decreases of hydrogen solubilities with increasing contents of other alloying metals have been used (95,104,108) in support of an essentially protonic nature of the hydrogen entities. However, in order to allow for proposed levels of electron donation it has seemed necessary to postulate adoptions of oxidation states by the alloying elements which can be difficult to reconcile with their relative positions in sequence of electronegaiivities.Moreover as for the palladium-hydrogen system, latterly there has been increasing emphasis on the account ...

Efficient separation of photogenerated electrons and holes, and associated surface reactions, is a crucial aspect of efficient semiconductor photocatalytic systems employed for photocatalytic hydrogen production. A new CoO /TiO /Pt photocatalyst produced by template-assisted atomic layer deposition is reported for photocatalytic hydrogen production on Pt and CoO dual cocatalysts. Pt nanoclusters acting as electron collectors and active sites for the reduction reaction are deposited on the inner surface of porous TiO nanotubes, while CoO nanoclusters acting as hole collectors and active sites for oxidation reaction are deposited on the outer surface of porous TiO nanotubes. A CoO /TiO /Pt photocatalyst, comprising ultra-low concentrations of noble Pt (0.046 wt %) and CoO (0.019 wt %) deposited simultaneously with one atomic layer deposition cycle, achieves remarkably high photocatalytic efficiency (275.9 μmol h ), which is nearly five times as high as that of pristine TiO nanotubes (56.5 μmol h ). The highly dispersed Pt and CoO nanoclusters, porous structure of TiO nanotubes with large specific surface area, and the synergetic effect of the spatially separated Pt and CoO dual cocatalysts contribute to the excellent photocatalytic activity.

Highy crystalline NiO nanoparticles are uniformly grown on the walls of carbon nanotubes (CNTs) by atomic layer deposition (ALD) at moderate temperature.Their size and stoichiometry are controlled by the ALD process parameters. The obtained NiO/CNT hybrids exhibit excellent performance in the electro-oxidation of methanol.

Two-dimensional (2D) molybdenum sulfide (MoS 2 ) is an attractive noble-metal-free electrocatalyst for hydrogen evolution (HER) in acids. Tremendous effort has been made to engineer MoS 2 catalysts with either more active sites or higher conductivity to enhance their HER activity. However, little attention has been paid to synergistically structural and electronic modulations of MoS 2 . Herein, 2D hydrogenated graphene (HG) is introduced into MoS 2 ultrathin nanosheets for the construction of a highly efficient and stable catalyst for HER. Owing to synergistic modulations of both structural and electronic benefits to MoS 2 nanosheets via HG support, such a catalyst has improved conductivity, more accessible catalytic active sites, and moderate hydrogen adsorption energy. On the optimized MoS 2 /HG hybrid catalyst, HER occurs with an overpotential of 124 mV at 10 mA cm −2 , a Tafel slope of 41 mV dec −1 , and a stable durability for 24 h continuous operation at 30 mA cm −2 without observable fading. The high performance of the optimized MoS 2 /HG hybrid catalyst for HER was interpreted with density functional theory calculations. The simulation results reveal that the introduction of HG modulates the electronic structure of MoS 2 to increase the number of active sites and simultaneously optimizes the hydrogen adsorption energy at S-edge atoms, eventually promoting HER activity. This study thus provides a strategy to design and develop high-performance HER electrocatalysts by employing different 2D materials.

Highly active electrode materials with judicious design in nanostructure are important for the construction of high-performance electrochemical energy storage devices. In this work, we have fabricated tubular TiC fibre cloth as an interesting type of stable supercapacitve materials.Hollow microfibres of TiC are synthesized by carbothermal treatment of commercial T-shirts cotton fibres. To demonstrate the rational of nanostructuring in energy storage, the hollow fibres are further covered by interwoven TiC nanotube branches, forming 3D tubular all-TiC hierarchical fibres with high electrical conductivity, high surface area, and high porosity. For energy storage functions, organic symmetric supercapacitors based on the hollow fibre-nanotube (HFNT) TiC cloth electrodes are assembled and thoroughly characterized. The TiC-based electrodes show very stable capacitance in long charge/discharge cycles and at different temperatures. In particular, the integrated TiC HFNT cloth electrodes show a reasonably high capacitance (185 F/g at 2 A/g), better cycling stability at high-rates (e.g., 97% retention at room temperature after 150,000 cycles, and 67% at −15 o C after 50,000 cycles) than other control electrodes (e.g., pure carbon fibre cloths). It is envisaged that these 3D tubular TiC fibres cloth is also useful for solar cells and electrocatalysis. Preparation of carbon fibre cloth supported carbon nanofibres (CFC+CNF) electrodes. The CFC+CNF electrodes were prepared by EPD of carbon nanofibres on CFC. The EPD process was the same as that aforementioned. The mass of CFC+CNF electrode is about 5.8 mg/cm 2 .Characterization of integrated electrodes. The phase and microstructure of samples were characterized by X-ray diffraction (XRD, RIGAKU D/Max-2550 with Cu Kα radiation), field emission scanning electron microscopy (FESEM, FEI SIRION), high-resolution transmission electron microscopy (HRTEM, JEOL JEM-2010F), Raman spectroscopy (WITec-CRM200 Raman system with a laser wavelength of 532 nm), Fourier transform infrared (FTIR) spectroscopy (Perkin Elmer System 2000 FTIR interferometer) and X-ray photoelectron spectroscopy (XPS, PHI 5700). The surface areas of smples were determined by BET measurements using a NOVA-1000e surface area analyzer.Supercapacitor fabrication and electrochemical measurements. The electrochemical performances of the TiC HFNT integrated electrodes were tested in CR2025 coin-type symmetric supercapacitors, in which the TiC HFNT electrodes were used as both the positive and negative electrodes without any

In this article, ZnO nanorods (NRs) were grafted on Ti-based vertically aligned TiO 2 nanotubes (NTs) by a feasible seed-induced hydrothermal reaction. Through such a simple but interesting structure combination of the two semiconductors, a novel composite photocatalytic anode of ZnO NRs/TiO 2 NTs with high efficiency was accordingly obtained. In this coupling, ZnO NRs could grow to flowerlike clusters directly grafted on the tops of TiO 2 NTs, acting just like a large number of lead wires, outstretched from the trunk TiO 2 NTs. Thus, the grafted ZnO NRs could serve conveniently as favorable hole channels and receptors for the efficient separation of photoelectrons and holes, which resulted in a slight shift of the band gap absorption edges and consequently changed the band gap energy (Eg). Moreover, the graft amount would further make a certain impact on the Eg. With an appropriate graft amount, ZnO NRs/TiO 2 NTs exhibited broader optical absorption range and higher photocatalytic activity than pure TiO 2 NTs or ZnO NRs did. Under the illumination of 365 nm UV light, the photoelectric conversion efficiency was enhanced from 7.0% of pure TiO 2 NTs to 23.6% of ZnO NRs/TiO 2 NTs. In the photoelectrocatalytic oxidation application, ZnO NRs/TiO 2 NTs exhibited higher removal ability for bisphenol A (BPA). The kinetic constant was 21.4 × 10 -5 s -1 , almost 2.3 times faster than that on pure TiO 2 NTs. Also, the stability of ZnO NRs was promoted on TiO 2 NTs with a stable BPA cyclic removal percentage because the receipted holes on ZnO NRs could prevent ZnO from photocorrosion efficiently.

Cuprous oxide (Cu(2)O) nanoparticles dispersed on reduced graphene oxide (RGO) were prepared by reducing copper acetate supported on graphite oxide using diethylene glycol as both solvent and reducing agent. The Cu(2)O/RGO composite exhibits excellent catalytic activity and remarkable tolerance to methanol and CO in the oxygen reduction reaction.

are more convenient and secure to be transported and stored. However, the conversion efficiencies of these AORs are commonly inferior to hydrogen oxidation. This is partially due to the sluggish kinetics of multielectrons' transferred processes inside alcohols (e.g., methanol, ethanol, ethylene glycol, and glycerol). [7][8][9][10][11] In this regard, various catalysts of both noble and non-noble metals have been designed and synthesized to boost such sluggish AORs. Although noble metal catalysts (e.g., Pd, Pt, and Rh) are more expensive than non-noble metals (e.g., Ni, Co, and Mn), their more negative AOR onset potentials make them superior for the construction of DAFCs, [4,5,11] originating from their unique electronic structures. Among reported noble-based catalysts, those based on the Pt metal are regarded as the star electrocatalysts for the AORs in terms of their oxidation overpotentials and Tafel slopes. [12,13] Notably, their alloys with other metals (e.g., Ru, Ni, Co, Pd, Rh, and Au) exhibit strong adsorption capability toward OH species or a so-called bifunctional mechanism, leading to improved AOR performance. [14][15][16][17] On the other hand, the serious poisoning effect of the carbonaceous intermediates (especially CO) hinders dramatically the activity of the used catalysts (especially the Pt catalysts) and eventually leads to much reduced conversion efficiencies of the AORs. [18,19] In this context, the screwlike PdPt alloy nanowires [19] and PdPt alloy nanoparticles [20] have been employed to replace single metallic Pt catalysts for methanol electro-oxidation reaction (MOR). Originating from varied electronic structures that are induced by the addition of Pd atoms, these PdPt alloys have been confirmed as commendable MOR catalysts. Although the sizes and compositions of these catalysts have been tuned and the AOR performance on these catalysts has been explored, the performance of these bimetallic heterostructures/catalysts is still far away for their commercial applications. The catalysts featuring superior AOR performance over those reported are still highly demanded for the construction of high-performance DAFCs.It has been well known that the optimization of these noble-metallic heterostructures/catalysts with respect to their morphologies and exposed facets is helpful to enhance their catalytic performance. [21][22][23][24] Among various heterostructures, a catalyst with a core-shell structure has been attracted special attention. [25][26][27][28][29][30] Its structure and its catalytic activity of the shell are revealed to be highly dependent on the used core. [31][32][33][34] This is because the strain effect (expansion or compression) can be Direct alcohol fuel cells (DAFCs) utilize alcohol electro-oxidation reactions (AORs) to provide electricity, where catalysts with optimal electronic structures are required to accelerate sluggish AORs. Herein, an electrocatalyst with an Au-nanorod core and a PdPt-alloy shell is designed. Its electronic structures are modulated through epitaxial growth ...