Flame Spray Pyrolysis as a Synthesis Platform to Assess Metal Promotion in In₂O₃‐Catalyzed CO₂ Hydrogenation

Abstract

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-made ternary Pd-In2O3-ZrO2 catalyst with enhanced oxygen vacancy generation for CO2 hydrogenation to methanol

“…12 kJ mol −1 ). The extremely low E a , app of the two reactions over Pd-ZrO 2 points towards CO and subsequently MeOH formation through the COOH intermediate on Pd nanoparticles being the predominant reaction mechanism 6 , 11 .

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“…1 ) was selected as a one-pot approach to produce a ternary Pd-In 2 O 3 -ZrO 2 catalyst targeting atomic distributions of palladium and indium on zirconia. Additionally, this method was applied to prepare In 2 O 3 , In 2 O 3 -ZrO 2 , Pd-ZrO 2 , and Pd-In 2 O 3 catalysts for comparative purposes while other reference materials were attained by optimized wet impregnation (WI) and co-precipitation (CP) protocols available elsewhere 4 , 6 , 11 . Details on the synthesis and notation of the catalysts are provided in the Supplementary Methods and Supplementary Tables 1 and 2 .…”

“…Additionally, while critically important to guide catalyst assembly and rationalize its impact on performance, quantification of oxygen vacancies on In 2 O 3 -based systems remains elusive. Their assessment predominantly focuses on confirming their formation, which has been demonstrated using electron paramagnetic resonance, nuclear magnetic resonance, Raman, and X-ray photoelectron spectroscopies 1 , 4 , 6 , 9 – 11 . However, to our knowledge, no attempt has been made to quantify the effects of the catalyst composition and architecture on the oxygen vacancy density.…”

A generalized machine learning framework to predict the space-time yield of methanol from thermocatalytic CO2 hydrogenation

“…3a) [8,33,34]. This pre-conception is justified in the case of Pd-and Pt-doped In 2 O 3 catalysts, in particular when these promoters are atomically dispersed, as this speciation boosts the catalytic activity by suppressing CO formation [35]. In the case of Pd-based catalysts, the most commonly used supports were CeO 2 and ZnO.…”

Emerging single atom catalysts in gas sensors

“…In order to evaluate the promotion effect of various metal promoters in In 2 O 3 in CO 2 hydrogenation to methanol, Javier Pérez-Ramírez et al employed FSP as a unified synthetic protocol to assess In 2 O 3 promotion by introducing nine metal promoters (0.5 wt%) into In 2 O 3 . 70 Fig. 3(c) shows the scheme of the FSP method for the preparation of M-In 2 O 3 catalysts.…”