Abstract
Palladium promotion and deposition on
monoclinic
zirconia are effective strategies to boost the performance of bulk In
2
O
3
in CO
2
-to-methanol and could unlock superior reactivity if well ...integrated into a single catalytic system. However, harnessing synergic effects of the individual components is crucial and very challenging as it requires precise control over their assembly. Herein, we present ternary Pd-In
2
O
3
-ZrO
2
catalysts prepared by flame spray pyrolysis (FSP) with remarkable methanol productivity and improved metal utilization, surpassing their binary counterparts. Unlike established impregnation and co-precipitation methods, FSP produces materials combining low-nuclearity palladium species associated with In
2
O
3
monolayers highly dispersed on the ZrO
2
carrier, whose surface partially transforms from a
tetragonal
into a
monoclinic-
like structure upon reaction. A pioneering protocol developed to quantify oxygen vacancies using in situ electron paramagnetic resonance spectroscopy reveals their enhanced generation because of this unique catalyst architecture, thereby rationalizing its high and sustained methanol productivity.
A plethora of metal promoters have been applied to enhance the performance of In2O3 in CO2 hydrogenation to methanol, a prospective energy carrier. However, the lack of systematic catalyst ...preparation and evaluation precludes a direct comparison of their speciation and promotional effects, and consequently, the design of an optimal system. Herein, flame spray pyrolysis (FSP) is employed as a standardized synthesis method to introduce nine metal promoters (0.5 wt.%) into In2O3. Methanol productivity generally increased on M‐In2O3 with selectivity following Pd ≈ Pt > Rh ≈ Ru ≈ Ir > Ni ≈ Co > Ag ≈ In2O3 > Au. In‐depth characterization, kinetic analyses, and theoretical calculations reveal a range of metal‐dependent speciation which dictate catalyst architecture and degree of promotion. Atomically‐dispersed promoters (Pd, Pt, Rh, Ru, and Ir) grant the highest improvement in performance, particularly Pd and Pt, which markedly promote hydrogen activation while hindering undesired CO formation. In contrast, metals in clustered (Ni and Co) and nanoparticle (Ag and Au) forms display moderate and no promotion, respectively. This study provides an atomic‐level understanding of In2O3 promotion based on a unified protocol, and highlights the potential of FSP to engineer complex catalytic systems toward more efficient energy transformations.
Flame spray pyrolysis is used as a standardized synthesis method to study promotional effects of nine transition metals in In2O3‐catalyzed CO2 hydrogenation to methanol. The nature of the promoter determines the catalyst architecture (single atoms, clusters, and nanoparticles) and corresponding reactivity, as examined by in‐depth characterization, kinetic analyses, and theoretical calculations.
Mixed zinc‐zirconium oxides, ZnZrOx, are highly selective and stable catalysts for CO2 hydrogenation to methanol, a pivotal energy vector. However, their activity remains moderate, and descriptors to ...design improved systems are lacking. This work applies flame spray pyrolysis (FSP), a one‐step and scalable method, to synthesize a series of ZnZrOx catalysts, and systematically compares them to coprecipitated (CP) analogs to establish deeper synthesis–structure–performance relationships. FSP systems (up to 5 mol%) generally display a threefold higher methanol productivity compared to their CP counterparts. In‐depth characterization and theoretical simulations show that, unlike CP, FSP maximizes the surface area and formation of atomically dispersed Zn2+ sites incorporated in lattice positions within the ZrO2 surface, which is key to improving performance. Analysis by in situ electron paramagnetic resonance (EPR) spectroscopy reveals that the specific architecture of the flame‐made catalyst markedly fosters the generation of oxygen vacancies. Together with surrounding Zn and Zr‐O atoms, the oxygen vacancies create active ensembles that favor methanol formation through the formate path while suppressing undesired CO production, as confirmed by kinetic modeling. This study elucidates the nature of active sites and their working mechanism, pushing forward ZnZrOx‐catalyzed methanol synthesis by providing a new benchmark for this cost‐effective and earth‐abundant catalyst family.
Flame spray pyrolysis (FSP) enables the design of superior ZnZrOx catalysts for CO2 hydrogenation to methanol. Synthesis–structure–performance relationships are derived through a comparative study using FSP and state‐of‐the‐art coprecipitated systems in combination with in‐depth characterization, theoretical calculations, and kinetic modeling. The zinc speciation and location determine catalyst surface area, the nature of active sites, and their corresponding reactivity.
At the remote International Chemistry Olympiad 2022 hosted by China, two outstanding students from Switzerland won one bronze medal and one honorable mention. A joint remote participation to the ...event of the delegations from Germany, Austria, and Switzerland could be realized in Basel with the support of the University of Basel. The International Chemistry Olympiad 2023 will be hosted at ETH Zurich. This itinerary will mark the first time this annual event comes to Switzerland.
Abstract Metal promotion could unlock high performance in zinc-zirconium catalysts, ZnZrO x , for CO 2 hydrogenation to methanol. Still, with most efforts devoted to costly palladium, the optimal ...metal choice and necessary atomic-level architecture remain unclear. Herein, we investigate the promotion of ZnZrO x catalysts with small amounts (0.5 mol%) of diverse hydrogenation metals (Re, Co, Au, Ni, Rh, Ag, Ir, Ru, Pt, Pd, and Cu) prepared via a standardized flame spray pyrolysis approach. Cu emerges as the most effective promoter, doubling methanol productivity. Operando X-ray absorption, infrared, and electron paramagnetic resonance spectroscopic analyses and density functional theory simulations reveal that Cu 0 species form Zn-rich low-nuclearity CuZn clusters on the ZrO 2 surface during reaction, which correlates with the generation of oxygen vacancies in their vicinity. Mechanistic studies demonstrate that this catalytic ensemble promotes the rapid hydrogenation of intermediate formate into methanol while effectively suppressing CO production, showcasing the potential of low-nuclearity metal ensembles in CO 2 -based methanol synthesis.
At the remote International Chemistry Olympiad 2022 hosted by China, two outstanding students from Switzerland won one bronze medal and one honorable mention. A joint remote participation to the ...event of the delegations from Germany, Austria, and Switzerland could be realized in Basel with the support of the University of Basel. The International Chemistry Olympiad 2023 will be hosted at ETH Zurich. This itinerary will mark the first time this annual event comes to Switzerland.
Methanol Synthesis
In article number 2204122, Javier Pérez‐Ramírez and co‐workers apply flame spray pyrolysis to design superior ZnZrOx catalysts for methanol synthesis from CO2. ...Synthesis‐structure‐performance relationships are established, revealing that zinc speciation and location determine catalyst architecture, the nature of catalytic ensembles, and the corresponding reactivity.
Abstract
Mixed zinc‐zirconium oxides, ZnZrO
x
, are highly selective and stable catalysts for CO
2
hydrogenation to methanol, a pivotal energy vector. However, their activity remains moderate, and ...descriptors to design improved systems are lacking. This work applies flame spray pyrolysis (FSP), a one‐step and scalable method, to synthesize a series of ZnZrO
x
catalysts, and systematically compares them to coprecipitated (CP) analogs to establish deeper synthesis–structure–performance relationships. FSP systems (up to 5 mol%) generally display a threefold higher methanol productivity compared to their CP counterparts. In‐depth characterization and theoretical simulations show that, unlike CP, FSP maximizes the surface area and formation of atomically dispersed Zn
2+
sites incorporated in lattice positions within the ZrO
2
surface, which is key to improving performance. Analysis by in situ electron paramagnetic resonance (EPR) spectroscopy reveals that the specific architecture of the flame‐made catalyst markedly fosters the generation of oxygen vacancies. Together with surrounding Zn and Zr‐O atoms, the oxygen vacancies create active ensembles that favor methanol formation through the formate path while suppressing undesired CO production, as confirmed by kinetic modeling. This study elucidates the nature of active sites and their working mechanism, pushing forward ZnZrO
x
‐catalyzed methanol synthesis by providing a new benchmark for this cost‐effective and earth‐abundant catalyst family.
Flame Spray Pyrolysis
In article number 2103707, Núria López, Javier Pérez‐Ramírez and co‐workers apply flame spray pyrolysis as a standardized synthesis method to investigate promotional effects of ...nine transition metals in In2O3‐catalyzed CO2 hydrogenation to methanol, revealing that catalyst architecture (single atoms, clusters, and nanoparticles) and corresponding reactivity are dictated by the nature of the promoter.
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