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22 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2, 3 [Next/Last]

Instruments / Technical Area	Publication Details	Published
B18-Core EXAFS	Empowering catalyst supports: a new concept for catalyst design demonstrated in the Fischer-Tropsch synthesis Motlokoa Khasu , Wijnand Marquart , Patricia J. Kooyman , Charalampos Drivas , Mark Isaacs , Alexander J. Mayer , Sandie E. Dann , Simon Kondrat , Michael Claeys , Nico Fischer Acs Catalysis 1, 6862 - 6872 DOI: 10.1021/acscatal.3c00924 Open Access Show Abstract ▼ Abstract: The Fischer–Tropsch (FT) synthesis is traditionally associated with fossil fuel consumption, but recently this technology has emerged as a keystone that enables the conversion of captured CO2 with sustainable hydrogen to energy-dense fuels and chemicals for sectors which are challenging to be electrified. Iron-based FT catalysts are promoted with alkali and transition metals to improve reducibility, activity, and selectivity. Due to their low concentration and the metastable state under reaction conditions, the exact speciation and location of these promoters remain poorly understood. We now show that the selectivity promoters such as potassium and manganese, locked into an oxidic matrix doubling as a catalyst support, surpass conventional promoting effects. La1–xKxAl1–yMnyO3−δ (x = 0 or 0.1; y = 0, 0.2, 0.6, or 1) perovskite supports yield a 60% increase in CO conversion comparable to conventional promotion but show reduced CO2 and overall C1 selectivity. The presented approach to promotion seems to decouple the enhancement of the FT and the water–gas shift reaction. We introduce a general catalyst design principle that can be extended to other key catalytic processes relying on alkali and transition metal promotion.	May 2023
	Humin formation on SBA-15-pr-SO3H catalysts during the alcoholysis of furfuryl alcohol to ethyl levulinate: effect of pore size on catalyst stability, transport, and adsorption Graziano Di Carmine , Costanza Leonardi , Luke Forster , Min Hu , Daniel Lee , Christopher M. A. Parlett , Olga Bortolini , Mark Isaacs , Alessandro Massi , Carmine D’agostino Acs Applied Materials & Interfaces DOI: 10.1021/acsami.3c04613 Open Access Show Abstract ▼ Abstract: Herein, the alcoholysis of furfuryl alcohol in a series of SBA-15-pr-SO3H catalysts with different pore sizes is reported. Elemental analysis and NMR relaxation/diffusion methods show that changes in pore size have a significant effect on catalyst activity and durability. In particular, the decrease in catalyst activity after catalyst reuse is mainly due to carbonaceous deposition, whereas leaching of sulfonic acid groups is not significant. This effect is more pronounced in the largest-pore-size catalyst C3, which rapidly deactivates after one reaction cycle, whereas catalysts with a relatively medium and small average pore size (named, respectively, C2 and C1) deactivate after two reaction cycles and to a lesser extent. CHNS elemental analysis showed that C1 and C3 experience a similar amount of carbonaceous deposition, suggesting that the increased reusability of the small-pore-size catalyst can be attributed to the presence of SO3H groups mostly present on the external surface, as corroborated by results on pore clogging obtained by NMR relaxation measurements. The increased reusability of the C2 catalyst is attributed to a lower amount of humin being formed and, at the same time, reduced pore clogging, which helps to maintain accessible the internal pore space.	May 2023
B18-Core EXAFS E01-JEM ARM 200CF	Isolated PdO sites on SiO2-supported NiO nanoparticles as active sites for allylic alcohol selective oxidation Aleksandra Ziarko , Thomas J. A. Slater , Mark A. Isaacs , Lee J. Durndell , Christopher M. A. Parlett Catalysis Science & Technology 40 DOI: 10.1039/D3CY00198A Diamond Proposal Number(s): [21795, 15151] Open Access Show Abstract ▼ Abstract: Catalytic allylic alcohol oxidation to aldehydes is an industrial process that necessitates chemoselectivity. Surface PdO (on Pd) enables this transformation but does not represent optimal metal utilisation. Here we report a facile synthesis route to produce isolated surface PdO catalytic sites on an earth-abundant metal (NiO) for cinnamyl alcohol oxidation.	May 2023
B18-Core EXAFS	The hydrogenation of crotonaldehyde on PdCu single atom alloy catalysts Mohammed J. Islam , Marta Granollers Mesa , Amin Osatiashtiani , Martin J. Taylor , Mark A. Isaacs , Georgios Kyriakou Nanomaterials 13 DOI: 10.3390/nano13081434 Diamond Proposal Number(s): [19850] Open Access Show Abstract ▼ Abstract: Recyclable PdCu single atom alloys supported on Al2O3 were applied to the selective hydrogenation of crotonaldehyde to elucidate the minimum number of Pd atoms required to facilitate the sustainable transformation of an α,β-unsaturated carbonyl molecule. It was found that, by diluting the Pd content of the alloy, the reaction activity of Cu nanoparticles can be accelerated, enabling more time for the cascade conversion of butanal to butanol. In addition, a significant increase in the conversion rate was observed, compared to bulk Cu/Al2O3 and Pd/Al2O3 catalysts when normalising for Cu and Pd content, respectively. The reaction selectivity over the single atom alloy catalysts was found to be primarily controlled by the Cu host surface, mainly leading to the formation of butanal but at a significantly higher rate than the monometallic Cu catalyst. Low quantities of crotyl alcohol were observed over all Cu-based catalysts but not for the Pd monometallic catalyst, suggesting that it may be a transient species converted immediately to butanol and or isomerized to butanal. These results demonstrate that fine-tuning the dilution of PdCu single atom alloy catalysts can leverage the activity and selectivity enhancement, and lead to cost-effective, sustainable, and atom-efficient alternatives to monometallic catalysts.	Apr 2023
B18-Core EXAFS	Integrated carbon capture and utilization: Synergistic catalysis between highly dispersed Ni clusters and ceria oxygen vacancies Hongman Sun , Yu Zhang , Chunfen Wang , Mark A. Isaacs , Ahmed I. Osman , Yehong Wang , David Rooney , Youhe Wang , Zifeng Yan , Christopher M. A. Parlett , Feng Wang , Chunfei Wu Chemical Engineering Journal 437 DOI: 10.1016/j.cej.2022.135394 Diamond Proposal Number(s): [19850] Show Abstract ▼ Abstract: Integrated carbon capture and utilization (ICCU) presents an ideal solution to address anthropogenic carbon dioxide (CO2) emissions from industry and energy sectors, facilitating CO2 capture and subsequent utilization through conversion into high-value chemicals, as opposed to current release into the atmosphere. Herein, we report the synergistic coupling of porous CaO, as a sorbent for CO2 capture, and Ni doped CeO2 nanorods, as catalytic sites for CO2 reduction. It is found that ceria is shown to possess the capacity for CO2 utilization, however, critically it only results in the generation of CO due to the weak CO-ceria bonding. The addition of Ni active sites gives rise to CH4 being the predominant product, via the strong interaction between Ni species and CO, which facilitates further reduction. Through tuning Ni loadings, we have evaluated the role of catalytic active site size, with a Ni loading of only 0.5 wt% providing optimal performance through the formation of sub-nanometer sized clusters. This near-atomic active site dispersion gives rise to CH4 productivity and selectivity of 1540 mmol g−1 Ni and 85.8%, respectively, with this optimal combination of catalyst and sorbent demonstrating high stability over 10 cycles of ICCU process. These observations in parallel with the synergistic coupling of earth-abundant, low-cost materials (CaO and Ni) will have broad implications on the design and implementation of high efficiency, cost-effective ICCU materials and processes.	Jun 2022
I09-Surface and Interface Structural Analysis	Insights into post-growth doping and proposals for CdTe:In photovoltaic devices Luke Thomas , Theo D. C. Hobson , Laurie J. Phillips , Kieran J. Cheetham , Neil Tarbuck , Leanne A. H. Jones , Matthew J. Smiles , Chris H. Don , Pardeep K. Thakur , Mark Isaacs , Huw Shiel , Stephen Campbell , Vincent Barrioz , Vin Dhanak , Tim Veal , Jonathan D. Major , Ken Durose Journal Of Physics: Energy DOI: 10.1088/2515-7655/ac7ad5 Diamond Proposal Number(s): [28268] Open Access Show Abstract ▼ Abstract: This paper is motivated by the potential advantages of higher doping and lower contact barriers in CdTe photovoltaic devices that may be realized by using n- type rather than the conventional p-type solar absorber layers. We present post-growth doping trials for indium in thin polycrystalline CdTe films using diffusion of indium metal and with indium chloride. Chemical concentrations of indium up to 1019 cm-3 were achieved and the films were verified as n-type by hard x-ray photoemission. Post growth chlorine treatment (or InCl3) was found to compensate the n-doping. Trial structures comprising CdS/CdTe:In verified that the doped absorber structures performed as expected both before and after chloride treatment, but it is recognized that this is not an optimum combination. Hence in order to identify how the advantages of n-type absorbers might be fully realized in future work, we also report simulations of a range of p-n junction combinations with n-CdTe, a number of which have the potential for high Voc.	Jun 2022
I09-Surface and Interface Structural Analysis	Evaluation of the thermal stability of TiW/Cu heterojunctions using a combined SXPS and HAXPES approach C. Kalha , M. Reisinger , P. K. Thakur , T.-L. Lee , S. Venkatesan , M. Isaacs , R. G. Palgrave , J. Zechner , M. Nelhiebel , A. Regoutz Journal Of Applied Physics 131 DOI: 10.1063/5.0086009 Diamond Proposal Number(s): [24248] Open Access Show Abstract ▼ Abstract: Power semiconductor device architectures require the inclusion of a diffusion barrier to suppress or at best prevent the interdiffusion between the copper metallization interconnects and the surrounding silicon substructure. The binary pseudo-alloy of titanium–tungsten (TiW), with >70 at. % W, is a well-established copper diffusion barrier but is prone to degradation via the out-diffusion of titanium when exposed to high temperatures (≥400 ∘C). Here, the thermal stability of physical vapor deposited TiW/Cu bilayer thin films in Si/SiO2(50 nm)/TiW(300 nm)/Cu(25 nm) stacks were characterized in response to annealing at 400 ∘C for 0.5 h and 5 h, using a combination of soft and hard x-ray photoelectron spectroscopy and transmission electron microscopy. Results show that annealing promoted the segregation of titanium out of the TiW and interdiffusion into the copper metallization. Titanium was shown to be driven toward the free copper surface, accumulating there and forming a titanium oxide overlayer upon exposure to air. Annealing for longer timescales promoted a greater out-diffusion of titanium and a thicker oxide layer to grow on the copper surface. However, interface measurements suggest that the diffusion is not significant enough to compromise the barrier integrity, and the TiW/Cu interface remains stable even after 5 h of annealing.	Apr 2022
	Continuous-flow synthesis of mesoporous SBA-15 Christopher M. A. Parlett , Hamidreza Arandiyan , Lee J. Durndell , Mark A. Isaacs , Antonio Torres Lopez , Roong J. Wong , Karen Wilson , Adam Lee Microporous And Mesoporous Materials 329 DOI: 10.1016/j.micromeso.2021.111535 Show Abstract ▼ Abstract: Ordered mesoporous silicas are widely used in separation science and catalysis, however, their slow batch synthesis is a barrier to scale-up and new applications. SBA-15 is one of the most extensively studied and commercially available mesoporous silicas, whose textural properties can be readily tuned through judicious choice of synthesis conditions. Here we demonstrate the continuous flow synthesis of SBA-15 in high yield at 80 °C using a simple tube reactor without any mixing device. The resulting SBA-15 exhibits excellent textural properties, with a BET surface area of 566 m2 g−1 and ordered 5.1 nm mesopore channels in a p6mm arrangement, akin to those from conventional batch synthesis, but with far higher productivity than previously reported in batch or flow (5.3 g L−1 h−1 versus 0.4 and 0.6 g L−1 h−1 respectively).	Nov 2021
B18-Core EXAFS	Palladium-doped hierarchical ZSM-5 for catalytic selective oxidation of allylic and benzylic alcohols Shengzhe Ding , Muhammad Ganesh , Yilai Jiao , Xiaoxia Ou , Mark Isaacs , Mark S'Ari , Antonio Torres Lopez , Xiaolei Fan , Christopher M. A. Parlett Royal Society Open Science 8 DOI: 10.1098/rsos.211086 Diamond Proposal Number(s): [15151] Open Access Show Abstract ▼ Abstract: Hierarchical zeolites have the potential to provide a breakthrough in transport limitation, which hinders pristine microporous zeolites and thus may broaden their range of applications. We have explored the use of Pd-doped hierarchical ZSM-5 zeolites for aerobic selective oxidation (selox) of cinnamyl alcohol and benzyl alcohol to their corresponding aldehydes. Hierarchical ZSM-5 with differing acidity (H-form and Na-form) were employed and compared with two microporous ZSM-5 equivalents. Characterization of the four catalysts by X-ray diffraction, nitrogen porosimetry, NH3 temperature-programmed desorption, CO chemisorption, high-resolution scanning transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy allowed investigation of their porosity, acidity, as well as Pd active sites. The incorporation of complementary mesoporosity, within the hierarchical zeolites, enhances both active site dispersion and PdO active site generation. Likewise, alcohol conversion was also improved with the presence of secondary mesoporosity, while strong Brønsted acidity, present solely within the H-form systems, negatively impacted overall selectivity through undesirable self-etherification. Therefore, tuning support porosity and acidity alongside active site dispersion is paramount for optimal aldehyde production.	Oct 2021
B18-Core EXAFS	PdCu single atom alloys supported on alumina for the selective hydrogenation of furfural Mohammed J. Islam , Marta Granollers Mesa , Amin Osatiashtiani , Jinesh C. Manayil , Mark A. Isaacs , Martin J. Taylor , Sotirios Tsatsos , Georgios Kyriakou Applied Catalysis B: Environmental 1 DOI: 10.1016/j.apcatb.2021.120652 Diamond Proposal Number(s): [19850] Show Abstract ▼ Abstract: Single-atom catalysts serve as a skilful control of precious metals on heterogenous catalysts where all active sites are accessible for catalytic reactions. Here we report the adoption of PdCu single-atom alloys supported on alumina for the selective hydrogenation of furfural. This is a special class of an atom efficient, single-site catalyst where trace concentrations of Pd atoms (0.0067 wt%) displace surface Cu sites on the host nanoparticle. Confirmed by EXAFS, the Pd atoms are entirely coordinated to Cu, with Pd-Cu bond lengths identical to that of a Cu-Cu bond. Selectively surface oxidised catalysts also confirm surface Pd atoms by EXAFS. These catalysts improve the conversion of furfural to furfuryl alcohol compared to monometallic catalysts, as they have the advantages of Cu (high selectivity but poor activity) and Pd catalysts (superior activity but unselective) without the drawbacks, making them the optimal catalysts for green/atom efficient catalysis.	Aug 2021

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