Mechanism of Methanol Synthesis from CO₂ Hydrogenation over Pt₈/In₂O₃ Catalysts: A Combined Study on Density Functional Theory and Microkinetic Modeling

Abstract

In 2 O 3 -based catalysts have attracted considerable attention in CO 2 hydrogenation to methanol reactions, thanks to their excellent CO 2 conversion rate and methanol selectivity. In this work, density functional theory combined with microkinetic modeling is employed to investigate the methanol synthesis mechanism over a Pt 8 /In 2 O 3 catalyst. First, a stable Pt 8 /In 2 O 3 (110) catalyst is modeled, where the Pt 8 cluster is positively charged. Second, the adsorption properties of the reaction species are optimized. It shows that H 2 is dissociated spontaneously to two H* adatoms on the Pt 8 cluster and the CO 2 * is adsorbed at the interface of Pt 8 /In 2 O 3 . Then three methanol synthesis channels are tested, that is, formate (HCOO), carboxyl (COOH), and RWGS + CO-Hydro routes. The calculations indicate that methanol is produced along with the order of CO 2 * → COOH* → CO* + OH* → HCO* → H 2 CO* → H 2 COH* → H 3 COH*. Finally, the channel is subjected to the microkinetic calculation at a pressure of 5 MPa and in a temperature range of 423 to 873 K. The degree of rate control analysis shows that H* adatom and COOH* dissociation TS7 are the rate-controlling adsorption and transition states, respectively. With the elevation of temperature, the turnover frequencies of CO and CH 3 OH increase, and the CH 3 OH selectivity decreases. They are related to the coverage of H* and COOH*.

CO2 Hydrogenation to Methanol on Indium Oxide-Supported Rhenium Catalysts: The Effects of Size

“…The other is the ability to load metals onto In 2 O 3 to form In 2 O 3 -supported metal catalysts. 4,20−37 The metal catalysts investigated thus far include palladium (Pd), 4,[20][21][22]38,39 platinum (Pt), 4,[23][24][25]40 nickel (Ni), 4,33−36 ruthenium (Ru), 4,30 rhodium (Rh), 4,28,29 gold (Au), 4,26,27 silver (Ag), 4,32 iridium (Ir), 4,31 and cobalt (Co). 4,37 Most of these metals are normally not active catalysts for CO 2 hydrogenation to methanol but are good for CO 2 methanation (CO 2 + 4H 2 ⇋ CH 4 + 2H 2 O, ΔH°2 98 K = −165.0 kJ/mol; ΔG°2 98 K = −113.5 kJ/mol) or for the reverse water gas shift reaction (RWGS; CO 2 + H 2 ⇋ CO + H 2 O, ΔH°2 98 K = +41.2 kJ/mol; ΔG°2 98 K = +28.6 kJ/mol).…”

“…One is the need to seek other oxides like ZrO 2 to form a solid solution with In 2 O 3 ,− for stabilization and optimization of oxygen vacancies in In 2 O 3 . The other is the ability to load metals onto In 2 O 3 to form In 2 O 3 -supported metal catalysts. ,− The metal catalysts investigated thus far include palladium (Pd), ,− ,, platinum (Pt), ,− , nickel (Ni), ,− ruthenium (Ru), , rhodium (Rh), ,, gold (Au), ,, silver (Ag), , iridium (Ir), , and cobalt (Co). , Most of these metals are normally not active catalysts for CO 2 hydrogenation to methanol but are good for CO 2 methanation (CO 2 + 4H 2 ⇋ CH 4 + 2H 2 O, Δ H ° 298 K = −165.0 kJ/mol; Δ G ° 298 K = −113.5 kJ/mol) or for the reverse water gas shift reaction (RWGS; CO 2 + H 2 ⇋ CO + H 2 O, Δ H ° 298 K = +41.2 kJ/mol; Δ G ° 298 K = +28.6 kJ/mol). , The latter is also a competitive side reaction for CO 2 hydrogenation to methanol. Previous studies suggested that there is a strong interaction between In 2 O 3 and the metal; changing the electronic structure of the metal creates additional active metal/In 2 O 3 interfacial sites, making it become both highly active and selective toward CO 2 hydrogenation to methanol. ,, …”

CO2 Hydrogenation to Methanol and Ethanol on In2O3-Based Single-Atom Catalysts and a New Scaling Relation

“…A ∼12 Å vacuum was used. Oxygen vacancies play an important role in CO 2 activation, ,, and the vacancy at the O 1 atom was demonstrated to be favorable for CO 2 activation and hydrogenation . Two In atoms, In 2 and In 3 , were adjacent to each O v1 .…”

CO2 Hydrogenation to Gasoline and Aromatics: Mechanistic and Predictive Insights from DFT, DRIFTS and Machine Learning

“…The insights derived from MKMs can serve as the basis for discovering new catalytic compositions with tunable structures possessing enhanced catalytic performance [45] . This can be attributed to its ability to reveal information such as degree of rate control (DRC), degree of selectivity control (DSC), and degree of chain growth control (DCGC), which are relevant parameters to simulate the kinetic behavior of the reaction system [48,49] . In the following paragraph, an attempt previously made to comprehensively describe CO 2 hydrogenation to higher hydrocarbons via DFT‐based MKM is described in detail.…”