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Silica particles were prepared by flame spray pyrolysis (FSP) as a support for nickel catalysts. The impact of precursor feed rate (3, 5 and 7 mL/min) during FSP on the silica characteristics and the ensuing effect on catalytic performance for the carbon dioxide, or dry, reforming of methane (DRM) was probed. Increasing the precursor feed rate: (i) progressively lowered the silica surface area from ≈340 m2/g to ≈240 m2/g; (ii) altered the silanol groups on the silica surface; and (iii) introduced residual carbon-based surface species to the sample at the highest feed rate. The variations in silica properties altered the (5 wt %) nickel deposit characteristics which in turn impacted on the DRM reaction. As the silica surface area increased, the nickel dispersion increased which improved catalyst performance. The residual carbon-based species also appeared to improve nickel dispersion, and in turn catalyst activity, although not to the same extent as the change in silica surface area. The findings illustrate both the importance of silica support characteristics on the catalytic performance of nickel for the DRM reaction and the capacity for using FSP to control these characteristics.

The vast chemical and structural tunability of metal–organic frameworks (MOFs) are beginning to be harnessed as functional supports for catalytic nanoparticles spanning a range of applications. However, a lack of straightforward methods for producing nanoparticle‐encapsulated MOFs as efficient heterogeneous catalysts limits their usage. Herein, a mixed‐metal MOF, NiMg‐MOF‐74, is utilized as a template to disperse small Ni nanoclusters throughout the parent MOF. By exploiting the difference in NiO and MgO coordination bond strength, Ni2+ is selectively reduced to form highly dispersed Ni nanoclusters constrained by the parent MOF pore diameter, while Mg2+ remains coordinated in the framework. By varying the ratio of Ni to Mg in the parent MOF, accessible surface area and crystallinity can be tuned upon thermal treatment, influencing CO2 adsorption capacity and hydrogenation selectivity. The resulting Ni nanoclusters prove to be an active catalyst for CO2 methanation and are examined using extended X‐ray absorption fine structure and X‐ray photoelectron spectroscopy. By preserving a segment of the Mg2+‐containing MOF framework, the composite system retains a portion of its CO2 adsorption capacity while continuing to deliver catalytic activity. The approach is thus critical for designing materials that can bridge the gap between carbon capture and CO2 utilization. [ABSTRACT FROM AUTHOR]

Rising levels of CO2 accumulation in the atmosphere have attracted considerable interest in technologies capable of CO2 capture, storage and conversion. The electrochemical reduction of CO2 into high-value liquid organic products could be of vital importance to mitigate this issue. The conversion of CO2 into liquid fuels by using photovoltaic cells, which can readily be integrated in the current infrastructure, will help realize the creation of a sustainable cycle of carbon-based fuel that will promote zero net CO2 emissions. Despite promising findings, significant challenges still persist that must be circumvented to make the technology profitable for large-scale utilization. With such possibilities, this Minireview presents the current high-performing catalysts for the electrochemical reduction of CO2 to liquid hydrocarbons, address the limitations and unify the current understanding of the different reaction mechanisms. The Minireview also explores current research directions to improve process efficiencies and production rate and discusses the scope of using photo-assisted electrochemical reduction systems to find stable, highly efficient catalysts that can harvest solar energy directly to convert CO2 into liquid hydrocarbons. [ABSTRACT FROM AUTHOR]

A stable and selective electrocatalyst for CO2 reduction was fabricated by covalently attaching graphitic carbon nitride onto multiwall carbon nanotubes (g-C3N4/MWCNTs). The as-prepared composite is able to reduce CO2 exclusively to CO with a maximum Faraday efficiency of 60 %, and no decay in the catalytic activity was observed even after 50 h of reaction. The enhanced catalytic activity towards CO2 reduction is attributed to the formation of active carbon-nitrogen bonds, high specific surface area, and improved material conductivity of the g-C3N4/MWCNT composite. [ABSTRACT FROM AUTHOR]

Silica particles were prepared by flame spray pyrolysis (FSP) as a support for nickel catalysts. The impact of precursor feed rate (3, 5 and 7 mL/min) during FSP on the silica characteristics and the ensuing effect on catalytic performance for the carbon dioxide, or dry, reforming of methane (DRM) was probed. Increasing the precursor feed rate: (i) progressively lowered the silica surface area from ≈340 m2/g to ≈240 m2/g; (ii) altered the silanol groups on the silica surface; and (iii) introduced residual carbon-based surface species to the sample at the highest feed rate. The variations in silica properties altered the (5 wt %) nickel deposit characteristics which in turn impacted on the DRM reaction. As the silica surface area increased, the nickel dispersion increased which improved catalyst performance. The residual carbon-based species also appeared to improve nickel dispersion, and in turn catalyst activity, although not to the same extent as the change in silica surface area. The findings illustrate both the importance of silica support characteristics on the catalytic performance of nickel for the DRM reaction and the capacity for using FSP to control these characteristics. [ABSTRACT FROM AUTHOR]

The presence of defects in a catalyst support is known to benefit catalytic activity. In this work, a He-plasma treatment-based strategy for introducing and stabilising defects on a Ni/TiO2 catalyst for photothermal CO2 hydrogenation was established. The impact of pretreatment step sequence—which comprised He-plasma treatment and reduction/passivation—on defect generation and stabilisation within the support was evaluated. Characterisation of the Ni/TiO2 catalysts indicated that defects created in the TiO2 support during the initial plasma treatment stage were then stabilised by the reduction/passivation process, (P-R)Ni/TiO2. Conversely, performing reduction/passivation first, (R-P)Ni/TiO2, invoked a resistance to subsequent defect formation upon plasma treatment and consequently, poorer photothermal catalytic activity. The plasma treatment altered the metal-support interaction and ease of catalyst reduction. Under photothermal conditions, (P-R)Ni/TiO2 reached the highest methane production in 75 min, while (R-P)Ni/TiO2 required 165 min. Decoupling the impacts of light and heat indicated thermal dominance of the reaction with CO2 conversion observed from 200 °C onwards. Methane was the primary product with carbon monoxide detected at 350 °C (~2%) and 400 °C (~5%). Overall, the findings demonstrate the importance of pretreatment step sequence when utilising plasma treatment to generate active defect sites in a catalyst support. [ABSTRACT FROM AUTHOR]

The present study provides an efficient process for the high-yield production of formic acid (24%) by reduction of carbon dioxide (CO 2 ) with potassium borohydride at ambient conditions. The effects of reaction temperature, CO 2 pressure and borohydride concentration have been investigated. For a 0.5 M borohydride solution, 0.15 mol/L of formic acid were produced at room temperature and ambient pressure with yields increasing at higher pressures. A time-resolved in situ 1 H and 11 B nuclear magnetic resonance (NMR) technique was firstly developed to monitor the elementary reaction processes under real working conditions. Direct evidence is given for the formation of H 2 , HD and a hydroxyborohydride intermediate (BH 3 OH − ) formed during borohydride decomposition indicating that the source of the hydrogen gas comes from both the borohydride anion and water, while borohydride works as a water-splitting reagent. Consequently, a reaction mechanism involved in both borohydride hydrolysis and CO 2 reduction has been established. [ABSTRACT FROM AUTHOR]

Illuminating thermal catalysts with visible light is an effective strategy to reduce the thermal requirements of CO 2 methanation. In this study, we systematically varied the cobalt loading and properties of xCo/CeO 2 catalysts (between 0 and 10 wt%) to understand changes in the visible light-assisted reaction mechanism with cobalt loading. 10Co/CeO 2 had the highest CO 2 conversion of 90% at 450 °C. The light promoted the CO 2 conversion of all catalysts from 300 to 450°C, peaking for 7.5Co/CeO 2 with a 125% improvement relative to thermal conditions (300 °C) before diminishing for 10Co/CeO 2. The light facilitated the conversion of the formate intermediate adsorbed onto CeO 2. In-situ DRIFTS and DFT unveiled a particle size trade-off between maximising CO 2 adsorbed at the Co-Ce interface while minimising CO 2 adsorbed onto cobalt, which is required for the best light enhancement. These findings underscore the importance of careful deposit size optimisation to unlock the light-assisted methanation's full potential. [Display omitted] • Contribution of visible light can be maximised with an optimal deposit size. • CO 2 adsorption onto large cobalt deposits limits the contribution of visible light. • Trade-off between CO 2 and H 2 on cobalt deposits required for best photo-enhancement. • One-step flame spray pyrolysis made Co/CeO2 with controllable deposit sizes by varying Co loading. [ABSTRACT FROM AUTHOR]

Hydrogen (H 2) generation using Steam Methane Reforming (SMR) is at present the most economical and preferred pathway for commercial H 2 generation. This process, however, emits a considerable amount of CO 2 , ultimately negating the benefit of using H 2 as a clean industrial feedstock and energy carrier. That has prompted growing interest in enabling CO 2 capture from SMR for either storage or utilisation and producing zero-emission "blue H 2 ". In this paper, we propose a spatial techno-economic framework for assessing blue hydrogen production SMR hubs with carbon capture, utilisation and storage (CCUS), using Australia as a case study. Australia offers a unique opportunity for developing such 'blue H 2 ' hubs given its extensive natural gas resources, availability of known carbon storage reservoirs and an ambitious government target to produce clean/zero-emission H 2 at the cost of A$2.7 kg H2 −1). On the other hand, Western Australia offers lower gas pricing and relatively lesser storage costs, which would lead to more economically favourable hydrogen production (

Photoreforming ethanol to simultaneously produce hydrogen and value-added organic products was realized over defected TiO 2. Chemically induced defects in TiO 2 promoted light absorption and charge separation, enhancing overall photoactivity. The induced defects also regulated product selectivity, leading to greater hydrogen purity and liquid to gaseous carbon ratio. The optimal catalyst generated 0.08 mmol/hr of hydrogen with a purity greater than 99 % and 0.08 mmol/hr of liquid acetaldehyde over a 6 hr timeframe. This was three times greater than the untreated TiO 2. Active species trapping revealed that the preferred ethanol oxidation pathway was direct hole transfer, indicating the selectivity relies on surface chemisorption. Surface defects decreased the acetaldehyde adsorption energy, instigating its prompt desorption and suppressing overoxidation into CO 2 , thus improving the selectivity towards hydrogen and liquid hydrocarbon products. The work offers an alternative approach towards sustainable energy by coupling photocatalysis with waste organic utilization. [Display omitted] • Defected TiO 2 prepared via a facile chemical reduction delivered improved product selectivity over ethanol photoreforming. • Enhanced light absorption and charge carrier separation by the TiO 2 defects elevated photoreforming activity. • The defected TiO 2 gave higher H 2 and acetaldehyde selectivity by suppressing CO 2 generation from ethanol over-oxidation. • Surface defects contributed to selectivity enhancement by altering intermediate chemisorption. [ABSTRACT FROM AUTHOR]

Flame spray pyrolysis (FSP) was used to design silica/ceria-zirconia particles with assorted structures as Ni catalyst supports for the carbon dioxide reforming of methane. The FSP precursor feed was varied to produce either mixed-oxide or core-shell arrays. The structures exhibited diversity in their properties including surface area and oxygen storage capacity. NiO deposit size decreased with increasing ceria-zirconia content, from 14 nm for the neat SiO 2 to 5 nm for the neat Ce 0.7 Zr 0.3 O 2 . Compared to the neat supports, the co-operative benefits of coupling the silica with the ceria-zirconia were clear. Introducing ceria-zirconia to the silica enabled the mixed supports to outperform the neat silica by supressing methane decomposition and promoting the dry reforming reaction. Introducing silica to the ceria-zirconia enabled the mixed supports to outperform the neat ceria-zirconia by decreasing susceptibility toward the reverse water gas shift reaction and preventing deactivation at 700 °C, attributed to better support thermal stability. [ABSTRACT FROM AUTHOR]

The work presented here evaluated the impact of reduction-oxidation-reduction (ROR) pre-treatment on 5 and 10% Ni-SiO 2 as an efficient and inexpensive manner of enhancing catalysts for the carbon dioxide reforming of methane. Samples were reduced, oxidised and subsequently re-reduced, with the Ni deposit characteristics being analysed at each step. It was demonstrated that ROR treatment decreased the average Ni deposit size and altered the interaction between the Ni and SiO 2 , which significantly enhanced catalytic performance. ROR pre-treatment resulted in an increase in CH 4 conversion, most significantly for the 10% Ni-SiO 2 samples (from 57% to 69% at 800 °C) with comparable carbon formation between the reduced and ROR pre-treated samples. During 600 °C stability tests the 10% reduced samples deactivated, due to carbon build-up, after 3–4 h reaction time. In contrast, at 600 °C the ROR sample maintained stable conversion after 6 h over a 12 h time frame. Additionally, for all samples ROR pre-treatment resulted in a more stoichiometric H 2 /CO ratio. The reduction in both Ni deposit size and crystallinity increased conversion and selectivity. This derived from a greater active metal surface area for conversion as well as a decrease in the prevalence of methane decomposition and the reverse water gas shift reaction by influencing the desorption of CO and lowering the occurrence of bulk NiO. Ultimately, ROR pre-treatment provides a simple and inexpensive means of improving dry reforming catalysts. [ABSTRACT FROM AUTHOR]

Catalytic methanol production from CO 2 hydrogenation at a lower temperature is limited, predominantly constricted by sluggish reaction kinetics. In this work, a ceria-modified Cu/ZnO/Al 2 O 3 catalyst (CuZnCe-Al) is fabricated which delivers efficient low-temperature methanol production (yield= 822 g/kg Cu /h and selectivity = 94% at 225 ºC and 20 bar) under light illumination. The influence of ceria loading on the morphology/microstructure, interfacial features, and surface chemistry of a Cu/ZnO-based catalyst is systematically assessed. Incorporating ceria (≤ 10 at%) into ZnO initially forms ZnO/CeO x interface which promotes both CO 2 chemisorption and the formate-pathway which favours methanol production over CO. Increasing the ceria loading beyond 10 at% invoked a Cu/CeO x -dominated structure, leading to over-stabilisation of the surface reaction species and a decreased preference for methanol. The photo-enhancement factor observed for each CuZn x Ce y catalysts is largely independent of the ceria loading, implying that ceria inclusion imposed little influence on the Cu-ZnO interfacial characteristics. [Display omitted] • Efficient low-temperature methanol production (822 g/kg Cu /h, 225 ºC under illumination) achieved over CuZnCe-Al catalyst. • ZnO/CeO x interface promotes the formate pathway for methanol production while suppressing CO production. • Cu/CeO x offers very poor methanol production likely due to the over-stabilization of surface species. [ABSTRACT FROM AUTHOR]

Highlights: [•] A facile one-pot, room temperature synthesis method was used to alter the MCM-41 support acidity. [•] It affords Ni-MCM-41 with unprecedented catalytic activity for the CO2 reforming of methane. [•] Controlling the acidity allows for the regulation of product selectivity (H2/CO ratio). [•] Varying MCM-41 support acidity alters the extent to which the various side reactions occur. [ABSTRACT FROM AUTHOR]

[Display omitted] • Light and heat energy were coupled to investigate the effects on catalytic CO 2 methanation. • Lanthanum addition to a Co/TiO 2 catalyst increased activity toward CO 2 methanation. • Cobalt crystallite size decreased with the addition of Lanthanum. • Lanthanum addition facilitated CO 2 adsorption and its subsequent activation under light. Utilising light and heat from the sun to drive CO 2 reduction into CH 4 is an effective approach to produce solar fuels. The effect of visible light illumination on the CO 2 methanation reaction, when catalysed by Co 10 /La x -TiO 2 , was explored. The results demonstrated that homogeneously dispersing lanthanum on the surface of TiO 2 boosted the catalytic activity of Co deposits under both non-illuminated (dark) and illuminated conditions. Illuminating the catalyst with a white LED (420 < λ < 800 nm) during the reaction lowered the activation energy and increased CO 2 conversion over the temperature range 250–450 °C. The most significant effect was observed for Co 10 /La 10 -TiO 2 where the activation energy was decreased by 20 % and the CO 2 conversion enhanced by 86 % at 350 °C. It was found that the basic sites introduced by La enhanced CO 2 adsorption and facilitated its activation. The present work illustrates how traditional thermal catalysts can be effectively modified to harness photoabsorption/plasmonic properties. [ABSTRACT FROM AUTHOR]