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This is Part II of an overview of the state-of-the-art and emerging technologies for decarbonising shipping using ammonia as a fuel. Part I (1) covered general properties of ammonia, the current production technologies with an emphasis on green synthesis methods, onboard storage and ways to generate power from it. The safety and environmental aspects, as well as challenges for the adaptation of technology to maritime structure, and an insight for the level of costs during fuel switching are now discussed to provide perspectives and a roadmap for future development of the technology.

Shipping, which accounts for 2.6% of global carbon dioxide emissions, is urged to find clean energy solutions to decarbonise the industry and achieve the International Maritime Organization (IMO)’s greenhouse gas (GHG) emission targets by 2050. It is generally believed that hydrogen will play a vital role in enabling the use of renewable energy sources. However, issues related with hydrogen storage and distribution currently obstruct its implementation. Alternatively, an energy-carrier such as ammonia with its carbon neutral chemical formula, high energy density and established production, transportation and storage infrastructure could provide a practical short-term next generation power solution for maritime industry. This paper presents an overview of the state-of-the-art and emerging technologies for decarbonising shipping using ammonia as a fuel, covering general properties of ammonia, the current production technologies with an emphasis on green synthesis methods, onboard storage and ways to generate power from it.

Understanding structural responses of metal–organic frameworks (MOFs) to external stimuli such as the inclusion of guest molecules and temperature/pressure has gained increasing attention in many applications, for example, manipulation and manifesto smart materials for gas storage, energy storage, controlled drug delivery, tunable mechanical properties, and molecular sensing, to name but a few. Herein, neutron and synchrotron diffractions along with Rietveld refinement and density functional theory calculations have been used to elucidate the responsive adsorption behaviors of defect-rich Zr-based MOFs upon the progressive incorporation of ammonia (NH3) and variable temperature. UiO-67 and UiO-bpydc containing biphenyl dicarboxylate and bipyridine dicarboxylate linkers, respectively, were selected, and the results establish the paramount influence of the functional linkers on their NH3 affinity, which leads to stimulus-tailoring properties such as gate-controlled porosity by dynamic linker flipping, disorder, and structural rigidity. Despite their structural similarities, we show for the first time the dramatic alteration of NH3 adsorption profiles when the phenyl groups are replaced by the bipyridine in the organic linker. These molecular controls stem from controlling the degree of H-bonding networks/distortions between the bipyridine scaffold and the adsorbed NH3 without significant change in pore volume and unit cell parameters. Temperature-dependent neutron diffraction also reveals the NH3-induced rotational motions of the organic linkers. We also demonstrate that the degree of structural flexibility of the functional linkers can critically be affected by the type and quantity of the small guest molecules. This strikes a delicate control in material properties at the molecular level.

2D nanosheets give enhanced surface area to volume ratios in particle morphology and they can also provide defined surface sites to disperse foreign atoms. Placing atoms of catalytic interest on 2D nanosheets as Single Atom Catalysts (SAC) represents one of the novel approaches due to their unique but tunable electronic and steric characteristics. Here in this mini-review, we particularly highlight some recent and important developments on heteroatom doped MoS2 nanosheets (SAC-MoS2) as catalysts for the electrochemical hydrogen evolution reaction (HER) from water, which could lead to opening up to a flagship of important renewable technologies in future. It is shown that the nature of dopants, doping positions and the polytypes of MoS2 nanosheets are the determining factors in the overall catalytic abilities of these functionalised nanosheets. This may serve to obtain atomic models which lead to further understanding of the 'metal-support interaction' in catalysis.

Understanding structural responses of metal-organic frameworks (MOFs) to external stimuli such as the inclusion of guest molecules and temperature/pressure has gained increasing attention in many applications, for example, manipulation and manifesto smart materials for gas storage, energy storage, controlled drug delivery, tunable mechanical properties, and molecular sensing, to name but a few. Herein, neutron and synchrotron diffractions along with Rietveld refinement and density functional theory calculations have been used to elucidate the responsive adsorption behaviors of defect-rich Zr-based MOFs upon the progressive incorporation of ammonia (NH

When ceria is used as a support for many redox catalysis involved in green catalysis, it is well-known that the overlying noble metal can gain access to a significant quantity of oxygen atoms with high mobility and fast reduction and oxidation properties under mild conditions. However, it is as yet unclear what the underlying principle and the nature of the ceria surface involved are. By using two tailored morphologies of ceria nanocrystals, namely cubes and rods, it is demonstrated from Scanning Transmission Electron Microscopy with Electron Energy Loss Spectroscopy (STEM-EELS) mapping and Pulse Isotopic Exchange (PIE) that ceria nanocubes terminated with a polar surface (100) can give access to more than the top most layer of surface oxygen atoms. Also, they give higher oxygen mobility than ceria nanorods with a non-polar facet of (110). A new insight for the possible additional role of polar ceria surface plays in the oxygen mobility is obtained from Density Functional Theory (DFT) calculations which suggest that the (100) surface sites that has more than half-filled O on same plane can drive oxygen atoms to oxidise adsorbate(s) on Pd due to the strong electrostatic repulsion.

There has been an intense research effort to develop 2-H MoS2 based catalysts to reduce or eliminate the use of Pt/C at higher metal loading for the hydrogen evolution reaction (HER) in catalytic hydrolysis of water, which enables the capture of renewable energy sources as fuel and chemical. However, the study of its uncommon polymorph, 1T-MoS2, and particularly the doping effect with transition metal (TM) is rather limited due to the instability of this phase. Here, we report a simple ambient temperature modification method using sonication to dope the single layer 1T-SMoS2 with various TM precursors. It is found that 1T-SMoS2 is more active than corresponding 2H-SMoS2 and the inclusion of 3 wt % Pt or Pd can also further enhance the HER activity. STEM-EELS and XAS show that the active single TM atom doping on this surface accounts for the high activity. Kinetic and DFT analyses also illustrate that the metallic nature of 1T-SMoS2 greatly facilitates the proton reduction step from water, rendering it non-rate-limiting in contrast to that of 2H-SMoS2. The inclusion of the TM single doper such as Pd, despite at low loading, can offer the dramatic acceleration of the rate limiting recombination of H to H2. As a result, a bifunctional catalysis for HER over this tailored composite structure is demonstrated that outperforms most reported catalysts in this area.

Herein, we present a systematic study on geometric and electronic effects exhibited by exposed Ag faceted nanoparticles and supports in the direct catalytic propylene epoxidation from O2 and propylene. Ag nanoparticles were first synthesised with well-defined morphologies (nanocubes or nanospheres) before they were placed on various supports, including conventional Al2O3 and a series of lanthanide oxides (Ln2O3). Results showed that faceted Ag nanoparticles and the oxide supports on their own are unable to deliver decent propylene oxide (PO) selectivity. However, their interfaces such as Ag nanocubes/La2O3 can dramatically enhance PO conversion (11.6%) and selectivity (51%) under dilute gas stream (3.33% C3H6 : 1.67% O2 : 95% He) at atmospheric pressure and 270 °C temperature. It is envisaged that the exposed (001) polar face on La2O3 with a higher density of oxygen vacancies facilitates dioxygen dissociation and the dissociated active oxygen is transferred to the Ag(100) surface at the interface where longer Ag–Ag interatomic distances prevent the removal of γ-H of propylene towards combustion, thus accounting for higher PO selectivity. These findings may lead to the design of new supported silver catalysts for environmentally-benign propylene oxide production.

Herein, we report the catalytic decarboxylation of γ-valerolactone (GVL) over Zn/ZSM-5 to butene, followed by aromatization at high yield with co-feeding of water. An evaluation of the catalytic performance after prolonged periods of time showed that a water molecule is essential to maintain the decarboxylation and aromatization activities and avoid rapid catalyst deactivation. Synchrotron X-ray powder diffraction and Rietveld refinement were then used to elucidate the structures of adsorbed GVL and immobilized Zn species in combination with EXAFS and NMR spectroscopy. A new route for the cooperative hydrolysis of GVL by framework Zn-OH and Brønsted acidic sites to butene and then to aromatic compounds has thus been demonstrated. The structures and fundamental pathways for the nucleophilic attack of terminal Zn-OH sites are comparable to those of Zn-containing enzymes in biological systems.

Despite a variety of T1-T2 dual-modal contrast agents (DMCAs) reported for magnetic resonance imaging (MRI), no tuning of local induced magnetic field strength of an DMCA, which is important to modulate the overall T1 and T2 responses for imaging delicate cells, tissues, and organs, is yet available. Here, we show that a spatial arrangement of T1 and T2 components within a "nano zone" in a single core-shell nanoparticle carrier (i.e., DMCA with core Fe3O4 and MnO clusters in a silica shell) to produce the necessary fine-tuning effect. It is demonstrated that this particle after the anti-CD133 antibody immobilization allows both T1 and T2 imaging at higher resolution for living ependynmal brain cells of rodents with no local damage under a strong MRI magnetic field. This study opens a route to rational engineering of DMCAs for accurate magnetic manipulations in a safe manner.

Ceria has been widely used as support in electrocatalysis for its high degree of oxygen storage, fast oxygen mobility, and reduction and oxidation properties at mild conditions. However, it is unclear what are the underlying principles and the nature of surface involved. By controlling the growth of various morphologies of ceria nanoparticles, it is demonstrated that the cubic-form of ceria, predominantly covered with higher energy polar surface (100), as support for Pd gives much higher activity in the electrocatalytic oxidation of formic acid than ceria of other morphologies (rods and spheres) with low-indexed facets ((110) and (111)). High-resolution transmission electron spectroscopy confirms the alternating layer-to-layer of cations and anions in (100) surface, and the electrostatic repulsion of oxygen anions within the same layers gives intrinsically higher oxygen vacancies on this redox active surface in order to reduce surface polarity. Density functional theory calculations suggest that the properties of fast oxygen mobility to reoxidize the CO-poisoned Pd may arise from the overdosed oxygens on these ceria surface layers during electro-oxidation hence sustaining higher activity.

Tagging recognition group(s) on superparamagnetic iron oxide is known to aid localization (imaging), stimulation and separation of biological entities using magnetic resonance imaging (MRI) and magnetic agitation/separation (MAS) techniques. Despite the wide applicability of iron oxide nanoparticle in T2-weighted MRI and MAS, the quality of image and safe manipulation of exceptionally delicate neural cells in a live brain are currently the key challenges. Here, we demonstrate the engineered manganese oxide clusters-iron oxide core-shell nanoparticle as a MR dual-modal contrast agent (DMCA) for the applications in neural stem cells imaging and magnetic manipulation in live rodent. As a result, using this engineered nanoparticle and associated technologies, identification, stimulation and transportation of labelled potentially multipotent neural stem cells from a specific location of a live brain to another by magnetic means for self-healing therapy can therefore be made possible.

Mesoporous silica SBA-15-supported bimetallic silver–nickel catalysts (Ag–Ni/SBA-15) were prepared by a co-impregnation method for the chemoselective hydrogenation of dimethyl oxalate (DMO) to methyl glycolate (MG). The structure and physicochemical properties of the catalysts were characterized using N 2 adsorption–desorption, X-ray fluorescence spectroscopy, transmission electron microscopy, H 2 -temperature-programmed reduction, UV–vis light diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, fourier-transform infrared spectroscopy and ester temperature-programed desorption. Compared with monometallic Ag or Ni catalyst, the bimetallic Ag–Ni/SBA-15 catalysts exhibited enhanced catalytic performance for the chemoselective hydrogenation of DMO to MG. The optimized Ag–Ni/SBA-15 catalyst with a Ni/Ag atomic ratio of 0.2 presented the highest MG yield and excellent catalytic stability during the hydrogenation of DMO to MG for longer than 140 h. The characterization results suggested that the Ag and Ni bimetallic nanoparticles on the catalyst surfaces likely formed a segregation structure with more Ni species in the core and more Ag in the shell, and electron transfer from Ni to Ag possibly occurred. The interactions between the Ag and Ni species generated more active/adsorption sites and prevented the transmigration of bimetallic nanoparticles during hydrogenation.

Semiconductive metal oxides are of great importance in environmental remediation and electronics because of their ability to generate charge carriers when excited with appropriate light energy. The electronic structure, light absorption and charge transport properties of the metal oxides have made possible their applications as photocatalysts. Recently, facet-engineering by morphology control has been intensively studied as an efficient approach to further enhance their photocatalytic performance. However, various processing steps and post-treatments used during the preparation of facet-engineered particles may generate different surface active sites which may affect their photocatalysis. Moreover, many traditional techniques (PL, EPR, XPS and Raman) used for materials characterization (oxygen vacancy, hydroxyl group, cation…etc.) are not truly surface specific but the analyses range from top few layers to bulk. Accordingly, they can only provide very limited information on the chemical states of the surface active features and distributions among facets, causing difficulty to unambiguously correlate facet-dependent results with activity. As a result, this always leads to different interpretations amongst researchers during the past decades. In this article, we will review on the controversies generated among researchers, when they correlated the performance of two most popular photocatalysts, ZnO and TiO2 with their facet activities based on characterization from the traditional techniques. As there are shortcomings of these techniques in producing truly facet-dependent features, some results can be misleading and with no cross-literature comparison. This review is also focussed on the new capability of probe-molecule-assisted NMR which allows a genuine differentiation of surface active sites from various facets. This surface-fingerprint technique has been demonstrated to provide both qualitative (chemical shift) and quantitative (peak intensity) information on the concentration and distribution of truly surface features. In light of the new technique this article will revisit the facet-dependent photocatalytic properties and shed light on these issues.

Functionalization of graphene is fundamental to facilitating its processing and offers a wide scope for advanced applications. Here we demonstrate a facile, highly efficient and mild covalent functionalization of graphene using HNO3 vapour. This results in functionalized few-layer graphene (FLG) that is high in both quantity and quality. We fully characterized the structure and defect level of functionalized FLG by X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy and Raman spectroscopy. The results from this analysis show the tunability of the surface oxygen functionalities of FLG achieved through controlling the oxidation temperature without affecting the major intrinsic properties of graphene. This allows for further doping for applications, for example with nitrogen as a metal-free catalyst in the oxygen reduction reaction.

It is shown that the catalytic properties of Pd can be fine-tuned by rationally varying the metal–support interaction through the formation of bimetallic nanoparticles with a support after hydrogen reduction; in the hydrogenolysis of a –CHOHCHOH– vicinal diol unit, the ability to break the C–C bond over the C–O bond is found to increase significantly with the decrease in d-band filling, while the ability to break the C–O bond is enhanced by the upshift of the d-band center of modified Pd.

By combining synchrotron X-ray powder diffraction, Rietveld refinement and the use of a probe molecule, Brønsted Acid Sites (BAS) of different strengths in steam-treated USY zeolite can be for the first time spatially differentiated: this enables the analysis of different acid-catalysed reactions of dimethylfuran (biomass) by the zeolite using a definitive site blockage strategy.

Hydrated niobium oxides are used as strong solid acids with a wide variety of catalytic applications, yet the correlations between structure and acidity remain unclear. New insights into the structural features giving rise to Lewis and Brønsted acid sites are presently achieved. It appears that Lewis acid sites can arise from lower coordinate NbO5 and in some cases NbO4 sites, which are due to the formation of oxygen vacancies in thin and flexible NbO6 systems. Such structural flexibility of Nb–O systems is particularly pronounced in high surface area nanostructured materials, including few-layer to monolayer or mesoporous Nb2O5·nH2O synthesized in the presence of stabilizers. Bulk materials on the other hand only possess a few acid sites due to lower surface areas and structural rigidity: small numbers of Brønsted acid sites on HNb3O8 arise from a protonic structure due to the water content, whereas no acid sites are detected for anhydrous crystalline H-Nb2O5.\ud \ud

Using physical mixtures of Pd/SWNTs (Pd nanoparticles on single-walled carbon nanotubes) and Pt/SWNTs, the composites show electro-catalytic properties comparable to the corresponding alloys: electron exchange readily occurs between the two metal nanoparticles via SWNT support at long ranges without direct atomic contact, which is responsible for the tunable alloy-like properties.

Neural stem cells (NSCs), which generate the main phenotypes of the nervous system, are multipotent cells and are able to differentiate into multiple cell types via external stimuli from the environment. The extraction, modification and re-application of NSCs have thus attracted much attention and raised hopes for novel neural stem cell therapies and regenerative medicine. However, few studies have successfully identified the distribution of NSCs in a live brain and monitored the corresponding extraction processes both in vitro and in vivo. To address those difficulties, in this study multi-functional uniform nanoparticles comprising an iron oxide core and a functionalized silica shell (Fe3O4@SiO2(FITC)-CD133, FITC: a green emissive dye, CD133: anti-CD133 antibody) have been strategically designed and synthesized for use as probe nanocomposites that provide four-in-one functionality, i.e., magnetic agitation, dual imaging (both magnetic resonance and optical) and specific targeting. It is shown that these newly synthesized Fe3O4@SiO2(FITC)-CD133 particles have clearly demonstrated their versatility in various applications. (1) The magnetic core enables magnetic cell collection and T2 magnetic resonance imaging. (2) The fluorescent FITC embedded in the silica framework enables optical imaging. (3) CD133 anchored on the outermost surface is demonstrated to be capable of targeting neural stem cells for cell collection and bimodal imaging.

It stems from the magnetism: The extraction of stem/progenitor cells from the brain of live animals is possible using antibodies conjugated to magnetic nanoparticles (Ab-MNPs). The Ab-MNPs are introduced to a rat's brain with a superfine micro-syringe. The stem cells attach to the Ab-MNPs and are magnetically isolated and removed. They can develop into neurospheres and differentiate into different types of cells outside the subject body. The rat remains alive and healthy.

Chemical vapor deposition (CVD) is used to grow thin films of 2D MoS2 with nanostructure for catalytic applications in the hydrogen evolution reaction (HER). Tailoring of the CVD parameters results in an optimized MoS2 structure for the HER that consists of large MoS2 platelets with smaller layered MoS2 sheets growing off it in a perpendicular direction, which increases the total number of edge sites within a given geometric area. A surface area to geometric area ratio of up to ∼340 is achieved, benefiting from the edge-exposed high-porosity network structure. The optimized thickness of the MoS2 film is determined for maximum performance, revealing that increasing thickness leads to increased impedance of the MoS2 film and reduced current density. The current density of the optimum sample reaches as high as 60 mA/cm2geo (normalized by geometric area) at an overpotential of 0.64 V vs RHE (in 0.5 M H2SO4), with a corresponding Tafel slope of ∼90 mV/dec and exchange current density of 23 μA/cm2geo. The lowered Tafel slope and large exchange current density demonstrate that the high-porosity edge-exposed MoS2 network structure is promising as a HER catalyst.

Exfoliated crystalline niobium oxides that contain exposed but interconnected NbO 6 octahedra with different degrees of structural distortion and defects are known to catalyze Brønsted acid (BA), Lewis acid (LA), and photocatalytic (PC) reactions efficiently but their structure–activity relationships are far from clear. Here, three exfoliated niobium oxides, namely, HSr 2 Nb 3 O 10 , HCa 2 Nb 3 O 10 , and HNb 3 O 8 , are synthesized, characterized extensively, and tested for selected BA, LA, and PC reactions. The structural origin for BA is associated mainly with acidic hydroxyl groups of edge-shared NbO 6 octahedra as proton donors; that of LA is associated with the vacant band position of Nb 5+ to receive electron pairs from substrate; and that of PC is associated with the terminal Nb=O of NbO 6 octahedra for photon capture and charge transfer to long-lived surface adsorbed substrate complex through associated oxygen vacancies in close proximity. It is believed that an understanding of the structure–activity relationships could lead to the tailored design of NbO x catalysts for industrially important reactions.

A major practical challenge in heterogeneous catalysis is to minimize the loading of expensive platinum group metals (PGMs) without degrading the overall catalytic efficiency. Gaining a thorough atomic-scale understanding of the chemical/structural changes occurring during catalyst manufacture/operation could potentially enable the design and production of "nano-engineered" catalysts, optimized for cost, stability and performance. In the present study, the oxidation behavior of a Pt-31 at% Pd alloy between 673-1073. K is investigated using atom probe tomography (APT). Over this range of temperatures, three markedly different chemical structures are observed near the surface of the alloy. At 673. K, the surface oxide formed is enriched with Pd, the concentration of which rises further following oxidation at 773. K. During oxidation at 873. K, a thick, stable oxide layer is formed on the surface with a stoichiometry of PdO, beneath which a Pd-depleted (Pt-rich) layer exists. Above 873. K, the surface composition switches to enrichment in Pt, with the Pt content increasing further with increasing oxidation temperature. This treatment suggests a route for tuning the surfaces of Pt-Pd nanoparticles to be either Pd-rich or Pt-rich, simply by adjusting the oxidation temperatures in order to form two different types of core-shell structures. In addition, comparison of the oxidation behavior of Pt-Pd with Pt-Rh and Pd-Rh alloys demonstrates markedly different trends under the same conditions for these three binary alloys. © 2012.

A correlation between ceria reducibility and the precious-metal d-band center is reported for ceria-supported precious-metal catalysts. The results could provide the missing link to fully explain the occurrence of strong metal-support interaction (SMSI) and hydrogen spillover in catalysts that consist of dispersed metals in contact with reducible metal oxides.

We report a simple but highly cooperative ensemble with CdS and MoS2 nanocrystals dispersed on graphene sheets: it is demonstrated that CdS nanocrystals can capture light energy and facilitate excited electron transfer to MoS2 for catalytic hydrogen production via the 2-D graphene which plays a key role as an efficient electron mediator.

The lasing behavior of solution-based colloidal quantum dots within an open microcavity is reported. The small size and wide tunability of the cavity provide single mode lasing over a wavelength range in excess of 25 nm. By extracting the lasing threshold and differential gain for the fundamental cavity mode over this spectral range, gain spectroscopy of the quantum dot solution is demonstrated. This new approach could help in the optimization of laser gain media and provides a way of constructing miniature laser arrays for on-chip integration.

The lasing threshold of the fundamental cavity mode is measured as a function of wavelength and single mode lasing is demonstrated for colloidal CdSe/CdS quantum dots and nanoplaletes using tunable open microcavities.

Single layer MoS2 synthesized by exfoliation with Li is demonstrated to take up the dye molecule, Eosin Y, with strong binding affinity via sulfur vacancies. This dye-sensitized single layer MoS2 ensemble exhibits remarkable activity and stability for photocatalytic hydrogen production from water.

Three different mesoporous silica (MS) samples were selected as template materials for designing novel, high-performance desiccants to give rapid-response temperature and humidity buffering in closed environments. The aim was to investigate how the functional properties of the MS materials can be tuned to suit differing psychrometric conditions in closed environments, and to inform the design process by conducting sensitivity analysis using building performance simulation software. Their humidity buffering performance was compared with other materials using WUFI Pro v5.1 to conduct numerical hygrothermal simulations. The MS materials had more than two orders of magnitude greater humidity buffering than traditional interior building materials (e.g. painted gypsum plaster) due to their high vapour storage capacity and high dynamic vapour sorption (DVS) response rates. Analysis showed that the gradient of the w 50-w 80 portion of the absorption branch isotherm is the most sensitive parameter when using the hygrothermal numerical model as a design tool for materials tuning. © 2013 Copyright International Building Performance Simulation Association (IBPSA).

The area of methanol synthesis and utilization has been attracting research interests due to its positive impact on the environment and also from energy perspectives. Methanol synthesis from CO2 hydrogenation not only produces methanol which is a key platform chemical and a clean fuel, but can also recycle CO2 which is one of the major greenhouse gases causing global warming. As a mobile energy carrier (particularly as a hydrogen carrier), methanol is a versatile molecule which is able to generate H2 via its decomposition. Catalysis plays a decisive role in the success of both methanol synthesis from CO2 hydrogenation and its reverse decomposition reaction. Pd/Ga2O3 binary catalyst has recently been identified as an active catalyst for the methanol synthesis reaction. In this thesis, it is reported the shape effect of Pd promoted Ga2O3 for this reaction. The catalytic H2 evolution from methanol photodecomposition has also been studied over these catalysts. Three shapes of Ga2O3 nanomaterials (i.e. rod and plate β-Ga2O3, and particle γ-Ga2O3) have been synthesized, followed by doping with Pd metal to form corresponding Pd/Ga2O3 nanocatalysts. It was found that a (002) polar Ga2O3 surface which was dominantly presented on the plate form was unstable, giving a higher degree of oxygen defects and mobile electrons in the conduction band than the other non-polar (111) and (110) surfaces of the rod form. It was shown that a significantly stronger metal support interaction was found between the (002) polar Ga2O3 on the plate form and Pd, which gave higher methanol yield and selectivity. For methanol photodecomposition, it was found that, for pure Ga2O3 catalysts of different shapes, the plate form with a highest degree of defects (unstable polar surface) could encourage a non-radiative catalytic recombination of electron and hole pairs upon irradiation, hence giving a highest photocatalytic activity for H2 production. Once Pd was introduced onto these oxide surfaces, it was noted that there was a fast and readily electron transfer from the conduction band of Ga2O3 to Pd due to the formation of a Schottky junction between the two materials. This produces metal sites for hydrogen production and further enhances the rate of the photocatalytic reaction over the radiative recombination of excitons. However, it was also found that at higher Pd content (>1%), the significantly shortened exciton lifetimes reduce the catalytic rate hence giving an overall volcanic response of activity to increasing Pd content for each shape of Ga2O3. At the higher Pd content, the plate form appeared to sustain a longer lifetime for photocatalysis compared to the other forms at the equivalent Pd loading.

Pt-based alloys containing Rh and Ru are effective catalysts in a range of applications, including pollution control and low-temperature fuel cells. As the Pt group metals are generally rare and expensive, minimizing the loading of them while also increasing the efficiency of catalyst materials is a continual challenge in heterogeneous catalysis. A smart method to "nanoengineer" the surface of the nanocatalyst particles would greatly aid this goal. In our study, the oxidation of a Pt-8.9 at. % Ru alloy between 773 and 973 K and the oxidation and oxidation/reduction behavior of a Pt-23.9 at. % Rh-9.7 at. % Ru alloy at 873 K for various exposure times were studied using atom probe tomography. The surface of the Pt-Ru alloy is enriched with Ru after oxidation at 773 K, whereas it is depleted in Ru at 873 K, and at 973 K. The surface oxide layer vanishes at higher temperatures, leaving behind a Pt-rich surface. In the case of the Pt-Rh-Ru alloy, oxidation initiates from the grain boundaries, forming an oxide with a stoichiometry of MO 2. As the oxidation time increases, this oxide evolves into a twophase nanostructure, involving a Rh-rich oxide phase (Rh, Ru) 2O 3 and a Ru-rich oxide phase (Ru, Rh)O 2. When this two-phase oxide is reduced in hydrogen at low temperatures, separate Rh-rich and Ru-rich nanoscale regions remain. This process could, therefore, be useful for synthesizing complex island structures on Pt-Rh-Ru nanoparticle catalysts. © 2012 American Chemical Society.

Platinum group metals (PGMs) are used in numerous catalyst applications, including conversion of engine exhaust gases and hydrocarbon reforming. Reducing the loading of PGMs without diminishing the overall catalyst activity is a major challenge. Fundamental studies of PGMs under reactive conditions can assist the design/synthesis of "nanoengineered" catalysts, tunable and optimized for cost, stability, and performance. In the present study, the oxidation and reduction behavior of a Pd-6.4 at. % Rh alloy is investigated following treatment at 873 K for various exposure times using atom-probe tomography. For short oxidation times (10 min), an oxide layer with PdO stoichiometry grows on the surface. As the oxidation time increases, two phases with stoichiometries of (Rh Pd )O and (Pd O) evolve. When the alloy is subsequently reduced in hydrogen, a nanoscale dispersion of Rh-rich metallic regions remains. This provides a route for the synthesis of multifunctional catalysts with different nanosurface regions in close proximity to one another. © 2012 American Chemical Society.