Cd/Pt Precursor Solution for Solar H-2 Production and in situ Photochemical Synthesis of Pt Single-atom Decorated CdS Nanoparticles

Despite extensive efforts to develop high-performance H2 evolution catalysts, this remains a major challenge. Here, we demonstrate the use of Cd/Pt precursor solutions for significant photocatalytic H2 production (154.7 mmol g−1 h−1), removing the need for a pre-synthesized photocatalyst. In addition, we also report simultaneous in situ synthesis of Pt single-atoms anchored CdS nanoparticles (PtSA-CdSIS) during photoirradiation. The highly dispersed in situ incorporation of extensive Pt single atoms on CdSIS enables the enhancement of active sites and suppresses charge recombination, which results in exceptionally high solar-to-hydrogen conversion efficiency of ≈1 % and an apparent quantum yield of over 91 % (365 nm) for H2 production. Our work not only provides a promising strategy for maximising H2 production efficiency but also provides a green process for H2 production and the synthesis of highly photoactive PtSA-CdSIS nanoparticles

Characterisation of the morphology of surface-assembled Au nanoclusters on amorphous carbon

In this study, aberration-corrected scanning transmission electron microscopy is employed to investigate the morphology of Au clusters formed from the aggregation of single atoms sputtered onto an amorphous carbon surface. The morphologies of surface-assembled clusters of N > 100 atoms are referenced against the morphologies of size-selected clusters determined from previously published results. We observe that surface-assembled clusters (at the conditions employed here) are approximately spherical in shape. The structural isomers of the imaged clusters have also been identified, and the distribution of structural types is broadly in agreement with those from size-selected cluster deposition sources. For clusters of approximately 147 atoms, we find a preference for icosahedra over decahedra and truncated octahedra, but at this size there is a high proportion of unidentified/amorphous structures. At around 309 atoms, we find a preference for decahedra over icosahedra and truncated octahedra, but over half the structures remain unidentifiable/amorphous. For sizes above approximately 561 atoms we are able to identify most of the structures, and find decahedra are still the most favoured, although in competition with single-crystal fcc morphologies. The similarity in structure between surface-assembled and size-selected clusters from a cluster source provides evidence of the relevance of size-selected cluster studies to clusters synthesised by other, industrially relevant, methodologies

Cd/Pt precursor solution for solar H2 production and in situ photochemical synthesis of Pt single-atom decorated CdS aanoparticles..

Despite extensive efforts to develop high-performance H2 evolution catalysts, this remains a major challenge. Here, we demonstrate the use of Cd/Pt precursor solutions for significant photocatalytic H2 production (154.7 mmol g−1 h−1), removing the need for a pre-synthesized photocatalyst. In addition, we also report simultaneous in situ synthesis of Pt single-atoms anchored CdS nanoparticles (PtSA-CdSIS) during photoirradiation. The highly dispersed in situ incorporation of extensive Pt single atoms on CdSIS enables the enhancement of active sites and suppresses charge recombination, which results in exceptionally high solar-to-hydrogen conversion efficiency of ≈1 % and an apparent quantum yield of over 91 % (365 nm) for H2 production. Our work not only provides a promising strategy for maximising H2 production efficiency but also provides a green process for H2 production and the synthesis of highly photoactive PtSA-CdSIS nanoparticles

Cd/Pt precursor solution for solar H 2 production and in situ photochemical synthesis of Pt single‐atom decorated CdS nanoparticles

Despite extensive efforts to develop high‐performance H2 evolution catalysts, this remains a major challenge. Here, we demonstrate the use of Cd/Pt precursor solutions for significant photocatalytic H2 production (154.7 mmol g−1 h−1), removing the need for a pre‐synthesized photocatalyst. In addition, we also report simultaneous in situ synthesis of Pt single‐atoms anchored CdS nanoparticles (PtSA‐CdSIS) during photoirradiation. The highly dispersed in situ incorporation of extensive Pt single atoms on CdSIS enables the enhancement of active sites and suppresses charge recombination, which results in exceptionally high solar‐to‐hydrogen conversion efficiency of ≈1 % and an apparent quantum yield of over 91 % (365 nm) for H2 production. Our work not only provides a promising strategy for maximising H2 production efficiency but also provides a green process for H2 production and the synthesis of highly photoactive PtSA‐CdSIS nanoparticles

Frame-by-frame observations of structure fluctuations in single mass-selected Au clusters using aberration-corrected electron microscopy

The multi-dimensional potential energy surface (PES) of a nanoparticle, such as a bare cluster of metal atoms, controls both the structure and dynamic behaviour of the particle. These properties are the subject of numerous theoretical simulations. However, quantitative experimental measurements of critical PES parameters are needed to regulate the models employed in the theoretical work. Experimental measurements of parameters are currently few in number, while model parameters taken from bulk systems may not be suitable for nanosystems. Here we describe a new measurement methodology, in which the isomer structures of a single deposited nanocluster are obtained frame-by-frame in an aberration-corrected scanning transmission electron microscope (ac-STEM) in high angle annular dark field (HAADF) mode. Several gold clusters containing 309 ± 15 atoms were analysed individually after deposition from a mass-selected cluster source onto an amorphous carbon film. The main isomers identified are icosahedral (Ih), decahedral (Dh) and face-centred-cubic (fcc) (the bulk structure), alongside many amorphous (glassy) structures. The results, which are broadly consistent with static ac-STEM measurements of an ensemble of such clusters, open the way to dynamic measurements of many different nanoparticles of diverse sizes, shapes and compositions

Zn loading effects on the selectivity of PdZn catalysts for CO2 hydrogenation to methanol

PdZn/TiO2 catalysts have been investigated for the hydrogenation of CO2 to methanol. Varying the ratio of Pd and Zn using TiO2 as a support has a dramatic effect on catalytic performance. Chemical vapour impregnation was used to produce PdZn alloys on TiO2 and X-ray diffraction, X-ray photoelectron spectroscopy, and scanning transmission electron microscopy revealed changes in the structure at varying total PdZn molar ratios. Compared to monometallic Pd/TiO2, introducing a low loading of Zn drastically changes product selectivity. When Pd is alloyed with Zn above a total Zn/Pd = 1 molar ratio, methanol selectivity is improved. Therefore, for enhanced methanol productivity, it is crucial for the Zn loading to be higher than that required for the stoichiometric formation of the 1:1 β-PdZn alloy

Methanol synthesis from CO2 and H2 using supported Pd alloy catalysts.

A number of Pd based materials have been synthesised and evaluated as catalysts for the conversion of carbon dioxide and hydrogen to methanol, a useful platform chemical and hydrogen storage molecule. Monometallic Pd catalysts shows poor methanol selectivity, but this is improved through the formation of Pd alloys, with both PdZn and PdGa alloys showing greatly enhanced methanol productivity compared with monometallic Pd/Al2O3 and Pd/TiO2 catalysts. Catalyst characterisation shows that the 1:1 β-PdZn alloy is present in all Zn containing post-reaction samples, including PdZn/Ga2O3, while the Pd2Ga alloy formed for the Pd/Ga2O3 sample. The heats of mixing were calculated for a variety of alloy compositions with high heats of mixing calculated for both PdZn and Pd2Ga alloys, with values of ca. -0.6 eV/atom and ca. -0.8 eV/atom, respectively. However, ZnO is more readily reduced than Ga2O3, providing a possible explanation for the preferential formation of the PdZn alloy, rather than PdGa. when in the presence of Ga2O3

Helical Magnetism and Structural Properties of β-Mn Structure Co(x)Zn(1-x) Thin Films

Thin films of polycrystalline β-Mn CoZn have been successfully grown on amorph-ous Si/SiO2 substrates by co-deposition sputtering from elemental targets. By this method a range of as-deposited Co(x)Zn(1−x) compositions were produced, which were annealed post-growth to reveal a splitting into two key phase elements. This splitting is into stoichiometrically correct β-Mn at the substrate across almost all com-positions except compositional ratio extremes, capped by a layer of ZnO from the surfactance of zinc through the film. Both of these layers preferentially order along their easy axis, this being〈221〉in the isotropic displacement corrected P4132/P4332 (β-Mn) CoZn, and〈002〉in ZnO. The β-Mn CoZn hence has polar order to the crystallites, which typically range on the order of 100–200 nm in lateral dimensions. Magnetic measurements show that the CoZn films deposited at ratios tuned to give the optimal volume fraction of β-Mn have an elevated TC up to ∼420 K, otherwise the TC typically appears to be 394–404 K in more cobalt deficient samples, and steadily increasing from ∼400 K with increasing cobalt content in cobalt rich samples. The samples have a saturating magnetisation of 16 emu/cc below the ideal volume fraction of β-Mn, which has a saturating magnetisation typically of 120 emu/cc, before again steadily increasing above this with increasing cobalt content. The magnetic behaviour is all consistent with the observations of compositionally dependent crystallite formation from growth studies, and both saturating magnetisation and TC of the optimal volume fraction of β-Mn are close to bulk values. Using polarised neutron reflectometry and fitting techniques in Refl1D a helical magnetic structure was determined to exist in a polycrystalline Co10Zn10 thin filmsample of ∼110 nm thickness. The helical wavelength is found to be ∼175 nm, which is in good agreement with literature of bulk studies, this helical structure is seen to unwind from 5 mT up to 700 mT, becoming indistinguishable from a simple collinear ferromagnetic state around 47 mT at 300 K. Crucially however, is the extension of the helical region from just below the TC at 380 K all the way down to room-temperature at 300 K, this is approximately 4× better than in bulk studies and extends the temperature bounds on any potential skyrmion phase. The potential for robust room-temperature skyrmion structures in these films with a wide temperature band in these materials is incredibly promising for development of skyrmion devices. In conclusion, the scope of study and improvement yet to be made for this class of alloy in thin films promises to be a rich and rewarding avenue, but direct observation of these topological structures is still required to fully attribute the measured effects and progress further