International Journal of Innovative Research and Scientific Studies, 3(2) 2020, pages: 53-63

Received 17 February 2020

Accepted 03 May 2020
Available online 09 May 2020

ISSN: 2617-6548

www.ijirss.com

Review Article

A brief review on the reaction mechanisms of CO2 hydrogenation into methanol

Jawed Qaderi1,2

1
Department of Chemistry, Faculty of Science, Universiti Teknology Malaysia, 81310 Skudai, Johor, Malaysia
2
Department of Physical Chemistry, Faculty of Chemistry, Kabul University, Kabul 1001, Afghanistan

Abstract
The catalytic reduction of CO2 to methanol is an appealing option to reduce greenhouse gas concentration as well as
renewable energy production. In addition, the exhaustion of fossil fuel, increase in earth temperature and sharp
increases in fuel prices are the main driving factor for exploring the synthesis of methanol by hydrogenating CO2.
Many studies on the catalytic hydrogenation of CO2 to methanol were published in the literature over the last few
decades. Many of the studies have presented different catalysts having high stability, higher performance, low cost,
and are immediately required to promote conversion. Understanding the mechanisms involved in the conversion of
CO2 is essential as the first step towards creating these catalysts. This review briefly summarizes recent theoretical
developments in mechanistic studies focused on using density functional theory, kinetic Monte Carlo simulations,
and microkinetics modeling. Based on these simulation techniques on different transition metals, metal/metal oxide,
and other heterogeneous catalysts surfaces, mainly, three important mechanisms that have been recommended are the
formate (HCOO), reverse water–gas shift (RWGS), and trans-COOH mechanisms. Recent experimental and
theoretical efforts appear to demonstrate that the formate route in which the main intermediate species is H2CO* in
the reaction route, is more favorable in catalytic hydrogenation of CO2 to chemical fuels in various temperature and
pressure conditions.

Keywords: CO2 hydrogenation, methanol synthesis, DFT, kMC, Reaction mechanism, RWGS

1. Introduction conditions and the nature of the catalyst applied. The

liquid yields like methanol are much favorable due to
The production of hydrocarbons, such as methanol
their application in lessening the lack of fossil fuels.
(CH3OH) from CO2/CO/H2 feeding, is a considerable
Methanol is synthesized by CO2 hydrogenation through
method which strongly depends on the reaction

*Corresponding author:
E-mail address: qaderi.j1992@graduate.utm.my

This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License., which permits
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CO2(g) + 3H2(g) = CH3OH(g) + H2O(g) reaction scheme, 2. Literature review

which is a reverse process of methanol-reforming at the
2.1 Formate (HCOO) Mechanism
same time. The standard enthalpy for this reaction at
room temperature is -49.3 kJ mol-1 [1]. This negative The main intermediate in the HCOO mechanism is
enthalpy means that the reaction is thermodynamically the formate (HCOO) in the reaction route. HCOO* has
desirable and that the reaction temperature has to be been believed to be the primary intermediate for
regulated to repel side and reverse reactions at a hydrogenating CO2 to CH3OH. Consequently, the rate-
moderately low level. Mostly, among all the metals, determining step (RDS) is thought to be regulated by
transition metals and their oxides are recognized as the HCOO* formation and hydrogenation. Accordingly,
effective catalysts to hydrogenate CO2 into methanol on previous theoretical studies focused mainly on revealing
a wider industrial range. The Cu/ZnO/Al2O3 catalyst is low-barrier steps in the industrial catalyst Cu/ZnO
actually used to industrially transform syngas mixtures following the development of HCOO* with regard to
(H2/CO2/CO) to methanol at the modest 50–100 bar unique Cu surface structures and Cu–oxide interactions
pressures and 473–573 K temperatures [1]. While, the [2]. Kopač et al. [3] used the first principles of DFT
basic catalytic mechanism and the active sites remain a calculations and kMC simulations to test the activation
major challenge. of carbon dioxide on the Cu(111) catalysts for methanol
synthesis. They applied the hydrogenation route model
Beginning from this species, the mechanism of CO2 resulting in the formate mechanistic steps. To
involves successive hydrogenations that ultimately lead state that the production of formaldehyde, H2COO + H
to methanol. Based on density functional theory (DFT) ↔ H2CO + OH, is the rate-determining step for the
calculations, kinetic Monte Carlo (kMC) simulations, synthesis of methanol. This step in the format pathway
microkinetic modeling, and in situ investigations on signifies the bottleneck even though it has the greatest
different Cu, Cu/metal oxide, and non-copper activation energy, but the CO2 hydrogenation remains as
heterogeneous catalysts surfaces, mainly, there are three the selectivity control step. They examined the
important mechanisms which have been recommended conversion, selectivity, and rate (TOF) dependence of
so far including the formate (HCOO), reverse water–gas the output of CH3OH on operating process conditions,
shift (RWGS), and trans-COOH mechanisms. The CO2 primarily temperature and pressure [3]. In methanol
hydrogenation process involves successive synthesis experiments using various Cu-type catalysts,
hydrogenations beginning with each precursor species the trends observed from their simulations, namely
ultimately leading to methanol [1]. This review higher selectivity at a higher pressure and lower
highlights briefly the reaction routes of the three temperature, higher conversion at higher pressure are in
mechanisms on different heterogeneous catalytic good agreement with their method. As well as, higher
systems and is discussed in the following section. TOF at higher pressure and temperature are commonly
seen supporting their method [3]. In addition, the
numerical stability analysis of kMC simulations has been
statistically checked for activation regarding random
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seed parameters and energy barriers. The distribution of comparison between ZnCu alloy behavior and ZnO/Cu
surface products has been observed to be particularly model catalysts for hydrogenation of CO2 into methanol
susceptible to the smallest disruptions of the activation was reported by Kattel et al. [2]. They carried out DFT
standard Gibbs energy [3]. Similarly, in accordance with calculations on the catalysts of the ZnCu and ZnO/Cu
the ab initio Hartree–Fock (HF) and the second-order model to achieve a further mechanistic understanding of
Møller–Plesset (MP2) calculations, Hu et al. [4] used the the methanol production from CO2. The findings from
dipped adcluster model (DAM) to test the hydrogenation their kMC simulations were consistent with the DFT
process of CO2 to methanol on a Cu(100) surface. They predictions under the experimental conditions, indicating
examined the promising reaction route with the that CO2 hydrogenation followed the format route on
Langmuir-Hinshelwood mechanism that initiated on the both catalyst systems. The HCOO* species are known on
basis of that Cu cluster model from the co-adsorption of pure Cu catalysts as merely viewer in production of
H2 and CO2 state. The chemisorbed CO2 appears in the methanol. The addition of Zn or ZnO helped to stabilize
Cu(100) DAM as a bent anionic CO−
2 species that bind the intermediate HCOOH* by direct Zn-O interaction for
all oxygen atoms to surface copper. They noticed five both ZnCu and ZnO/Cu systems and to activate HCOO*
succeeding hydrogenation steps for the conversion of by hydrogenation. Their results highlighted an interface
CO2 to methanol with the reaction pathway given in the Cu and ZnO synergy which facilitates the formate
following equations (* indicating the adsorbed species) intermediates formation to produce methanol [2].
[4]: Kakumoto et al. [5] also conducted ab initio calculations
using a density functional approach to test the stability of
CO2 + 2H → HCOO + H
* * * *
(1) the intermediate reaction in the production of methanol
HCOO* + H* → H2COO* (2) using clusters of Cu, CuO, and CuZnO. They provided
H2COO* + H* → H2CO* + OH* (3) some valuable insights but the models are too simplistic
when opposed to the catalyst's actual surfaces. Their
H2CO* + H* → H3CO* (4)
findings showed that CO2 and other intermediate
H3CO* + H* → H3COH (5)
reaction agents were able to adsorb on C+ sites while H2
OH + H → HOH
* *
(6)
molecules adsorb on Cu and ZnO to generate H atoms
Among all other steps, hydrogenation of adsorbed and ions.
formate to adsorbed dioxomethylene (HCOO* + H* →
H2COO*; Ea = 1.00 eV; ΔE = 0.74 eV) is the highest In addition to ZnO, zirconia (ZrO2) is also an

elementary barrier. Besides this, the hydrogenation of important promoter and supporter for the Cu catalyst.

adsorbed dioxomethylene producing formaldehyde was Hong and Liu [6] conducted a large study on the

another high barrier reaction intermediate with Ea = 0.74 hydrogenation reaction of CO2 on the surface of hybrid

eV [4]. Besides Cu and metal oxide supported Cu Cu/ZrO2 catalyst using DFT calculations and kMC

catalysts, the combined Zn with Cu and Cu oxides act as method to supply a comprehension understanding of the

the effective catalysts that show better performance in complex interfacial catalysis under experimental

hydrogenation reaction of CO2 into methanol. The direct circumstances. They demonstrated that both methanol

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and CO are generated primarily through the formate Al2O3 together with Cu and ZnO. The reaction
route, whereas the RWGS channel has only a slight mechanism of methanol production using the
involvement. Their theoretical findings showed that the Cu/ZnO/Al2O3 catalyst by CO2 hydrogenation was
key route at the oxygen-rich Cu/ZrO2 interface is the investigated by French et al. [8] using hybrid quantum
formate pathway initiated by direct CO2 hydrogenation, mechanics and molecular mechanics (QM/MM)
where H2CO* was a key intermediate reaction species. embedding computational technique. Their mechanisms
Their kinetics simulation results exhibited the CO2 proposed the formation of formate intermediate through
conversion selectivity towards methanol and lower CO2 chemisorption to produce methanol with further
activation energies for methanol in contrast to production hydrogenation of CO2. Their findings showed the
of CO. They also concluded that kMC is a more creation of interstitial surface sites of oxygen vacancy
appropriate tool in comparison with the microkinetics that are responsible for methanol synthesis. They
method for simulating heterogeneous catalytic processes explained the adsorption of essential precursors of
[6]. In addition, Tang and colleagues [7] researched the methanol including CO2, HCOO− and H3 CO− ions. The
catalytic kinetics of CO2 fastening to methanol over a interstitial oxygen site was the principal catalytically
Cu/ZrO2 binary catalyst using kMC simulations with active site for the formation of anionic adsorbates. Two
first principles. Two reaction pathways including the intermediate species, HCO− −
2 and H2 COO were found to
RWGS via CO2 decomposition to CO and hydrogenation be particularly stable. The former (the formate ion) is
through formate intermediate for methanol synthesis considered a stable long-lived intermediate, but the latter
were verified on the surface of Cu/ZrO2 catalyst. The has not been characterized experimentally although it is
selectivity as a result of theoretical studies were 85% and isomeric to the reported methoxy species [8].
15% for methanol and CO, respectively. In the reverse
The coupled-clusters singles and doubles theory
RWGS path, the CO release as a by-product was
[CCSD(T)] calculations were performed by Huš and his
predictable due to the existence of the CO2 splitting
colleagues [9] to test the thermodynamics and equilibria
channel. Although it is possible to recognize HCOO and
H2COO, but they are not the principal intermediate that of hydrogenation of CO2 into methanol by using spinel-

results in methanol. Theoretically, the hydrolysis route type catalyst Cu/ZnAl2O4. They evaluated the Gibbs free

plays an important role in the formation of methanol and energy, enthalpy, entropy, and chemical equilibrium
constants of the direct methanol synthesis and the
the removal of oxygen atom on the surface of the
opposing RWGS reaction at pressures 1, 20, 40, 60, and
catalyst, but the catalyst interface sites are commonly
100 bars and temperatures 25, 150, 200, 250, and 300ºC
occupied by oxidative species, such as O atoms, OH and
using ab initio quantum chemistry method of
H3CO groups, and, thus, the Cu atoms interface is
CCSD(T)/aug-cc-Pvqz. In addition, a thorough study of
cationic. The lack of active sites for CO2 adsorption
result in the low conversion rate of CO2 fixation. all possible intermediates in each elementary step,
adsorption/desorption energies, geometries, barriers and
The increased catalytic efficiency of the combined adsorption rate were performed using the DFT method
catalyst in CO2 hydrogenation highlights the position of of plane wave. The reaction pathway for methanol
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synthesis was via formate route as a result of their measurements using the PAW method based on DFT in
calculations, and the rate-limiting steps were the the periodic boundary state. They proved that the
formations of H2COO and H2COOH species. The role of reaction routes on the surfaces of Fe(111) and W(111)
the DFT in modeling the current non-copper catalytic catalysts for the CO2 hydrogenation were the same but
systems can also be reflected. Frei et al. [10] studied the the energies were dissimilar. Their calculation results
reaction mechanism and kinetic behavior of CO2 showed that the most possible way to hydrogenate the
hydrogenation on the surface of In2O3 catalyst. They CO2 on the surfaces of Fe(111) or W(111) catalysts, was
carried out DFT calculations using the Vienna Ab initio to construct a formate-vertical structure. They observed
Simulation Package (VASP) and the exchange- that all of the respective CO2 hydrogenation
correlation functional of the Perdew-Burke-Ernzerhof intermediates on the W(111) surface were more stable
(PBE). The core electrons were represented with a 500 than those on the Fe(111) equivalents, but all of the
eV plane-wave cut-off energy via projector Augmented W(111) surface reaction barriers were greater than those
Wave Pseudopotentials (PAW) for the valence electrons. on the Fe(111) analogs. It is due to the stronger
Theoretical modeling of CO2 hydrogenation over this interactions between adsorbates and the W(111) surface,
surface has shown that the oxygen vacancies generated which makes it more difficult to recombine H and CO2
under reaction conditions can activate CO2 and adsorbates compared to Fe(111) analogues.
heterolytically split H2. There was a description of the
The key argument in the HCOO process is the
plausible path to methanol which followed identical
formation of HCOOH* or H2COO* as the optimal
steps until the second addition of hydride. In this route,
product as a result of hydrogenation of HCOO*. The
CO2 was reduced along the path given in the following
HCOO mechanism has been proved to be more
equations [10]:
beneficial experimentally and theoretically in specific
CO2 + H → HCO2 (7) temperature and pressure environments for the catalytic
HCO2 + H → HCOOH (8) hydrogenation of CO2 to chemical fuels [1,4].

HCOOH + H → H2COOH (9)

2.2 The Reverse Water-Gas Shift Mechanism
H2COOH + H → H2C(OH)2 (10)
In the reverse water-gas shift reaction (RWGS)
H2C(OH)2 → H2CO + H2O (11)
mechanism, the key intermediate is considered to be CO*
H2CO + H → H3CO (12) instead of HCOO* as compared to the HCOO
H3CO + H → H3COH (13) mechanism. Simply it can be seen that the CH3O and CO

In this path methanediol formation is strongly favored. generations share the same pathway. The CO* species

They also led orders in methanol synthesis for reactants was created when the COOH* intermediate was

and products that usually matched the values which were hydrogenated, whereas HCOO* was considered a dead-

obtained experimentally. In addition, Li and Ho [11] end spectator species due to the experimental finding that

studied the CO2 hydrogenation on the surfaces of HCOO* hydrogenation kinetics did not suit that of

Fe(111) and W(111) catalysts with quantum-chemical methanol production. However, the RWGS route on pure

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Cu surfaces is at least not feasible as most the theoretical reaction pathway to be the RWGS + CO-Hydro. The CO
studies confirmed [1]. Yang et al. [12] found that formyl formed in the RWGS reaction can either desorb or
(HCO*) was not stable and chose to dissociate into CO* continue to react with hydrogen to produce CH4 or
and H* species instead of adopting the Cu reverse route. CH3OH. They found that while there are active low-
Consequently, only a small amount of CO* formed from coordinated sites, Pt nanoparticle itself cannot catalyze
the RWGS reaction on the surface of Cu catalyst could the reaction. The poor bonding to CO2 can impede the
be changed to methanol and much of CO* would be overall activity. The selectivity depends greatly on
desorbed on the surface, thereby considerably hindering parameters including binding energy of CO, and
methanol selectivity. In order to stabilize HCO*, energetics for intermediate reactions such as CO* + H* →
promoters or dopants were required. To enhance the CHO*, CH2OH* → CH2* + OH*, and CH2OH* + H* →
performance of Cu on methanol synthesis, the Cu-based CH3OH. The improved binding of CO and thus the
catalysts have been promoted or doped with various facilitated hydrogenation of CO* to HCO* prevents CO
elements [13]. Using a combination of DFT and KMC yield and improves the synthesis of CH4 or CH3OH [15].
simulations, Yang et al. [14] obtained the activity The emergence of CO has also been detected besides
sequence of different metal doped Cu towards methanol from COOH* hydrogenation by direct dissociation of
synthesis. It was obtained that the Ni-supported Cu CO2 on endorsed Cu catalysts. The experimental
nanoparticle showed the highest catalytic activity attempts on Cu/ZnO/Al2O3 [8] and DFT examination of
because of the HCO stabilization, i.e., Ni dopants in Cu Cu–ZrO2 ideal catalysts both verified that CO could be
nanoparticles may promote the formation of CH3OH synthesized by direct CO2 dissociation (CO2* → CO* +
through the RWGS mechanism and decrease the O*) without the key intermediate COOH*. For the
generation of CO side products, as many experimental purpose of testifying the probability of CO
studies have demonstrated [1]. hydrogenation to CH3OH concerning CO2 under
accurate reaction conditions, kMC simulations have been
Additionally, many forms of processed non-copper-
applied with a large time scale. The results exhibited that
based materials have remarkable catalytic performance
a ratio of 1:1 of CO2: CO mixture gas results in ∼2/3
in converting CO2 into CH3OH through RWGS
CH3OH generation by CO2 and ∼1/3 CH3OH by CO,
mechanisms. Through integrating DFT experiments,
whereas the CO2 gas itself gives ∼85% CH3OH and the
kMC simulations and experimental observations, Kattel
rest ∼15% is from dissociation of CO2 involving CO.
and colleagues [15] got a comprehension mechanism of
The kMC simulations showed that CO2 hydrogenation
CO2 hydrogenation on the Pt nanoparticles catalyst.
without CO* intermediate is predominant under the
They performed DFT calculations using the VASP code.
reaction conditions for CH3OH synthesis while CO
They used 400 eV plane-wave cutoff energy to calculate
hydrogenation leads to a small amount of CH3OH via the
total energy. The generalized gradient approximation
RWGS process [7].
(GGA) with the functional PW91 was used to explain the
electronic exchange and correlation effects. Their DFT The above discussions summarize that the RWGS
calculations and kMC simulations result confirmed the mechanism cannot be entirely excluded even though
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many theoretical studies declared the key intermediate to trans-COHOH* → CO* → HCO* → H2CO* → H3CO* →
be HCOO* in the formate route and CH3OH synthesis CH3OH, which was more desirable than formate
followed the HCOO mechanistic pathway. The average pathway from a kinetic viewpoint. The key intermediate
hydrogenation limit for CO was just marginally higher in this mechanistic route of CO2 hydrogenation on the
than that for HCOO* to hydrogenate to CH3OH. This surface of Cu(111) catalyst was COH* with a high
may account for the observed levels of divergence activation barrier. Upon the hydrogenation of COH*,
between the production rates of HCOO* and CH3OH [1]. CH3OH was synthesized, excluding the presence of both
In the section below, the methanol synthesis from the HCOO* and CO* intermediates [16]. Besides this, Tang
mixed CO2/H2 gas will be discussed in a debatably et al. [17] used the DFT calculation method on a stepped
different mechanism in the existence of water. surface of the Ga3Ni5(111) catalyst to analyze the
mechanistic route of CO2 hydrogenation to methanol.
2.3 Trans-COOH Mechanism
Their calculation results demonstrated that the possible
Water is a critical factor influencing the reaction route for conversion of CO2 into methanol using
thermocatalytic conversion of CO2 as seen in industrial Ga3Ni5 (111) catalyst is as the following equations [17]:
processes where the RWGS reactions can produce a
CO2 + H → trans-COOH (14)
considerable amount of gaseous water. Even though
Tang et al. [7] determined that the mechanism of HCOO trans-COOH + H → t,t-COHOH (15)

was overpowering in the synthesis of CH3OH from CO2, t,t-COHOH → t,c-COHOH (16)
they found that the difficulty in surface H* hydrogenation t,c-COHOH → c,c-COHOH (17)
*
of CH3O could be overwhelmed in the existence of H2O
c,c-COHOH → COH + OH (18)
through a smaller barrier. The theoretical studies
COH + H → HCOH (19)
indicated that water may influence CO2 hydrogenation
HCOH + H → CH2OH (20)
reaction barriers, and may even modify the preferred
reaction pathways. In a recent study, Zhao et al. [16] CH2OH + H → CH3OH (21)

suggested an alternative reaction pathway called the Remarkably, their findings showed that the formation of
trans-COOH* mechanism [16], with trans-COOH* trans-COOH species was not the rate-limiting step and
generation rather than HCOO* being the key limiting had a low activation barrier, however, H2O formation
step for Cu(111) due to the high hydrogenation barrier of from H and OH was observed as the rate-limiting step
* *
HCOO . It was observed that the trans-COOH with the lowest rate constant and highest activation
formation barrier could be lowered in the existence of barrier (0.85 eV). The summary of the three main
water and, therefore, promote the synthesis of CH3OH. reaction mechanisms, the corresponding computational
With water physisorbed or chemically absorbed, the CO2 and simulation methods, and rate-limiting steps during
hydrogenation barrier was reduced to 0.17 or 0.77 eV, CH3OH production by the hydrogenation of CO2 using
respectively, from 1.17 eV without water molecules. different heterogeneous catalysts are given in Table 1.
Their proposed trans-COOH* could rapidly change into
COHOH* and the RWGS mechanism pathway CO2* →
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Table 1: Summary of the comparison of the different heterogeneous catalytic systems, the corresponding computational and simulation methods, and
rate-limiting steps in the hydrogenation of CO2 into CH3OH.
Catalyst Computational/Simulation Method Reaction Mechanism Rate-Limiting Step (RLS) Ref.
Anatase TiO2(101) DFT (GGA-VASP) Formate (HCOO) CH2O + H → CH3O +
* * * *
[18]
Cu(100) DAM, HF, and MP2 Formate (HCOO) HCOO* + H* → H2COO* [14]
Cu(111) DFT (GGA-PW91) and Formate (HCOO) CH3O + H → CH3OH
* * *
[19]
Microkinetic model
Cu(111) DFT (GGA-PW91) Carboxyl (COOH) CO2* + H*→ COOH* +* [16]
Cu(111) DFT (GGA-PW91) H2O-promoted carboxyl (COOH) COHOH → COH + OH + * * * *
[16]
Cu(111) DFT (GGA-PW91) Formate (HCOO) H2COO +H → H2CO + OH +
* * * * *
[12]
Cu(111) DFT and kMC Formate (HCOO) H2COO* + H* ↔ H2CO* + OH* +* [3]
Cu/PbTiO3 DFT (VASP-PAW) and kMC Formate (HCOO) HCOO* + H* → H2COO* [20]
(Zacros 2.0)
Cu/ZnAl2O4 DFT (PWscf-PBE) and Formate (HCOO) HCOO* + H* → H2COO* +* [9]
CCSD(T)/aug-cc-pVQZ H2COO + H → H2COOH
* * *

Cu/ZnO DFT and kMC Formate )HCOO( - [2]

Cu/ZnO/Al2O3 DFT (GGA-PW91) and Formate (HCOO) CH3O + H → CH3OH
* * *
[19]
Microkinetic model
Cu/ZrO2 DFT (GGA-PBE) and kMC Formate (HCOO) CH3O* + H* → CH3OH* [7]
Cu29 DFT (GGA-PW91) Formate (HCOO) H2COO + H → H2CO + OH +
* * * * *
[12]
Fe(111) and W(111) DFT (VASP-PAW-rPBE) Carboxyl (COOH) CO2 + H → trans-COOH +
* * * *
[11]
or cis-COOH*
Ga3Ni5(111) DFT (GGA-VASP-PBE) and Carboxyl (COOH) H* + OH* → H2O [17]
Microkinetic model
In2O3(111) DFT (GGA-VASP-PBE) and Formate (HCOO) CH2O* + H* → CH3O* +* [10]
Microkinetic model
InZr3(110) DFT (GGA-PBE) RWGS+CO-hydrogenation HCO* + H* → H2CO* +* [21]
Mo6S8 DFT (GGA-PBE) RWGS+CO-hydrogenation CO + H → HCO +
* * * *
[22]
Pt(111) DFT (GGA) and Microkinetic model Carboxyl (COOH) COOH + → CO2 + H
* * * *
[23]
PdCu3 DFT (GGA-PW91) Carboxyl (COOH) HCOH* + H* → H2COH* +* [24]
Pd4/In2O3 DFT (VASP-GGA-PAW-PBE) and Formate (HCOO) H2COO + H → H2CO +OH
* * * *
[25]
Microkinetic model
Pt nanoparticle DFT (VASP-GGA-PW91) Formate (HCOO) HCOO* + H* → H2COO* [15]
Rh3Cu6(111) 3
DFT (DMol -GGA-PW91) RWGS+CO-hydrogenation CO2 + H → trans-COOH +
* * * *
[24]

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3 Conclusion References

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