Monodentate Formate Research Articles

In Situ Fourier Transform Infrared Investigation on the Low-Level Carbon Dioxide Conversion over a Nickel/Titanium Dioxide Catalyst.

Efficiently converting atmospheric carbon dioxide (CO2) is crucial for sustainable human development. In this study, we conducted systematic in situ Fourier transform infrared tests to examine how hydrogen (H2) partial pressure affects the conversion of low-level CO2 (around 400 ppm) using nickel/titanium dioxide (Ni/TiO2). Results show that increasing H2 partial pressure significantly increases surface monodentate formate species, leading to enhanced methane (CH4) production at both 250 and 400 °C. Conversely, on Ni's surface, the key species are formyls and bidentate formate at 250 °C, but these decrease significantly at 400 °C. These findings indicate that low-level CO2 is more easily converted to CH4 over Ni/TiO2 than Ni, regardless of temperature. Additionally, the strong Ni-TiO2 interaction gives Ni/TiO2 an advantage in converting low CO2 concentrations, with excellent durability even at 400 °C. This study enhances our understanding of direct CO2 conversion and aids in the development of advanced CO2 emission reduction technologies.

Exploring the nature of copper species: CeO2 support shape effect and its influence on CO2 hydrogenation to methanol

A series of CuO catalysts supported on CeO2 with different morphologies (nanorod, nanocube and hydrangea-like) were tested for the CO2 hydrogenation into methanol. Remarkable morphology-dependent CuO-CeO2 interaction was observed, which was associated with the types and concentrations of copper species. The best performance was obtained over the CuO/hydrangea-like-CeO2 catalyst, giving CO2 conversion of 15.6 % and methanol selectivity of 92.4 % at 260 °C and 3 MPa. The enhanced activity was due to the largest amount of small particle size of copper species, which was responsible for the facile activation of H2. Additionally, the Cu2+-Ov-Cex species facilitated the generation of oxygen vacancies and hydroxyl groups, these two species favored formate production and further hydrogenation to methanol. Moreover, in situ diffuse reflectance infrared fourier transform spectroscopy (in situ DRIFTS) results revealed that the both monodentate formate (m-HCOO*) and bidentate formate (bi-HCOO*) were key and necessary intermediate of CO2 hydrogenation to methanol. The proposed predominate reaction pathway was m-HCOO*→ b-*OCH3 → CH3OH and the minor one was bi-HCOO* → t-*OCH3 → CH3OH.

Microscopic insights into the reaction mechanism of Fe-based oxygen carrier with CH4 in chemical-looping combustion

Fe-based oxygen carriers are regarded as a promising class of oxygen carriers in the field of chemical looping combustion. However, the elucidation of the detailed microscopic reaction mechanism of oxygen carriers remains a significant challenge. In this work, we combine in situ spectroscopy, density-functional theory (DFT) calculations, and micro-kinetic modelling to reveal the microscopic reaction mechanism of CH4 combustion on α-Fe2O3. The macroscopic reaction characterization of hematite with CH4 was carried out on a fixed bed, and gas chromatography (GC) was utilized to detect the combustion products (CO2, H2O and H2). Subsequently, in situ spectroscopy and DFT were combined to reveal the detailed pathways for the CH₄ oxidation process. The results indicated that the reaction intermediates evolve from methoxy (CH3O*) to the bridged bidentate formate (b-HCOO*) to the monodentate formate (m-HCOO*), which ultimately leads to the formation of CO2 through a combination of H transfer and lattice oxygen oxidation. A micro-kinetic model was developed which incorporates surface reaction with the oxygen transport. This revealed that CH3O* and CH3O* → CH2OO* are the key intermediates and radical reactions, respectively, for CO2 production. The elucidation of the reaction mechanism may prove beneficial for the future development of novel Fe-based oxygen carriers.

Activity of CuCoCe layered double hydroxides catalysts and mechanism for C3H6-SCR

CuxCoyCez-LDH prepared with layered double hydroxides (LDHs) as precursors was calcined to form CuxCoyCezO catalysts which were experimentally investigated for the selective catalytic reduction of NO by C3H6 (C3H6-SCR) in a fixed bed micro-reactor in the presence of O2. The physical–chemical properties of the catalysts were characterized and analyzed with respect to the SCR reactivity. In situ DRIFTS study was conducted to investigate the intermediate species during the SCR reaction. Results showed that NO conversion was as high as 95 % at 225 °C over Cu0.21Co0.48Ce0.31O catalyst. The excellent activity of the catalyst could be attributed to the synergistic effect between Cu, Co, and Ce. The XRD results showed that the synergistic effect between the metals was because of the formation of the solid solution between Cu, Co, and Ce, which promoted the interaction and dispersion of the three active components. EDS mapping further proved this point. According to the XPS data, Cu and Co had a redox reaction that increased the number of oxygen vacancies favorable for NO adsorption and dissociation. The redox properties between Cu and Co was further confirmed to improve the catalytic activity by H2-TPR. Additionally, the results of BET and NH3-TPD demonstrated that the SCR catalytic activity was promoted by the right quantity of acidic sites and the specific surface area. In situ DRIFTS experiments provided a mechanism for the C3H6-SCR reaction on the catalyst and confirmed the formation of reaction intermediates such as bidentate and monodentate nitrate, formate, and acetate.

Enhancing methane formation in carbon dioxide hydrogenation on nickel clusters with zirconium additives: Exploring active sites, reaction pathways, and catalytic mechanisms

This study focuses on the catalytic reaction of carbon dioxide (CO2) hydrogenation using 0.5 wt% nickel (Ni) deposited on silica oxide support (SiO2). Initially, these Ni clusters exhibit limited catalytic activity and selectivity toward carbon monoxide (CO) formation. However, the introduction of zirconium ions (Zr4+) onto the Ni clusters leads to a remarkable improvement in the catalytic efficiency of CO2 hydrogenation and methane (CH4) production. The interaction between Ni and ZrO2 generates interfacial sites that play a multifaceted role. These sites facilitate the binding of acidic CO2 and promote the atomic hydrogen migration from ZrO2 to Ni. Consequently, the creation of interfacial sites on the Ni catalysts directly enhances the rate of CO2 hydrogenation while also increasing CH4 selectivity. The primary intermediate in this process appears to be monodentate formate species, which can undergo direct decomposition to CO or conversion into formic acid intermediates. The formic acid intermediates subsequently undergo hydrogenation, ultimately leading to the production of CH4.

Investigating the Role of Cs Species in the Toluene–Methanol Side Chain Alkylation Catalyzed by CsX Catalysts

The side chain alkylation of toluene with methanol was studied on a series of CsX catalysts prepared by varying the Cs species and ion exchange conditions. The effects of various parameters, such as the exchanging temperatures and times on the adsorption/activation properties of different CsX catalysts, were investigated by combining a variety of characterization means for understanding the role of Cs species in the side chain alkylation reaction. On the basis of the various characterization results and their related literature results, it can be proposed that the Cs ions located on the ion-exchanged sites of X zeolites could effectively adsorb and activate toluene molecularly through modifying the basicity of framework oxygen, whereas the cluster of cesium oxide (Cs2O) could ensure the effective conversion of methanol into formaldehyde. Additionally, Cs ions can promote the production of monodentate formate, which enhances the selectivity of styrene. However, too much Cs2O will lead to the excessive decomposition of methanol into CO2, CO, and H2, thus inhibiting the production of styrene. In summary, the presence of suitable amounts of Cs ions and Cs2O clusters plays a significant role in the formation of the side chain products of styrene and ethylbenzene.

Exploring the sustained release catalysis of CuAl2O4 spinel for highly effective CO2 conversion to CO

Sustained Release Catalysis concept has been demonstrated over Cu-based spinel catalysts to retard Cu agglomeration via gradually releasing active copper from spinel lattice during catalytic reaction. Herein, the solid-phase synthesized stoichiometric CuAl2O4 spinel is illustrated to be an effective sustained release catalyst for CO2 hydrogenation to CO (RWGS). Characterizations point out a mechanism that active Cu can be liberated from spinel lattice under the RWGS atmosphere, forming Cu-deficiency defect spinel with abundant surface hydroxyl groups on rearranged spinel Al ions. Cu entities and surface hydroxyls can well activate H2 and CO2, producing monodentate and bidentate formate species as crucial intermediates for CO, especially, the monodentate formate located on spinel octahedral AlVI presents superior dissociation performance and contributes more to the CO formation. The successful application of the Sustained Release Catalysis concept in RWGS provides significant insight for understanding the catalytic dynamics of Cu-spinel catalysts in CO2 hydrogenation process.

Operando DRIFTS Investigations on Surface Intermediates and Effects of Potassium in CO2 Hydrogenation over a K−Fe/YZrOx Catalyst

AbstractA detailed operando DRIFTS study on the CO2 Fischer‐Tropsch reaction with K‐promoted Fe/YZrOx catalysts was performed to investigate the influence of this modification on the catalytic performance in the formation of lower olefins as well as higher hydrocarbons and to gain insights into mechanistic aspects. Catalytic testing revealed an enhanced formation of olefins and hydrocarbons by adding potassium to the catalysts, while spectroscopic studies revealed various stable adsorbates and intermediates such as monodentate carbonates, bicarbonates, formates, formyl, and methoxy on the surface of the K‐promoted Fe/YZrOx catalysts compared to the unpromoted one. Based on gas‐feed switching experiments and statistical analysis of literature IR data regarding Fe‐containing catalysts, it was found that carbonate species interacting with H2 are transformed to higher hydrocarbons and methane via formate and formyl formation, while bicarbonate species are decomposed accompanied by the formation of CO, which then further reacts to form formate or formyl and finally hydrocarbons.

Water and Cu+ Synergy in Selective CO2 Hydrogenation to Methanol over Cu-MgO-Al2O3 Catalysts.

The CO2 hydrogenation reaction to produce methanol holds great significance as it contributes to achieving a CO2-neutral economy. Previous research identified isolated Cu+ species doping the oxide surface of a Cu-MgO-Al2O3-mixed oxide derived from a hydrotalcite precursor as the active site in CO2 hydrogenation, stabilizing monodentate formate species as a crucial intermediate in methanol synthesis. In this work, we present a molecular-level understanding of how surface water and hydroxyl groups play a crucial role in facilitating spontaneous CO2 activation at Cu+ sites and the formation of monodentate formate species. Computational evidence has been experimentally validated by comparing the catalytic performance of the Cu-MgO-Al2O3 catalyst with hydroxyl groups against that of its hydrophobic counterpart, where hydroxyl groups are blocked using an esterification method. Our work highlights the synergistic effect between doped Cu+ ions and adjacent hydroxyl groups, both of which serve as key parameters in regulating methanol production via CO2 hydrogenation. By elucidating the specific roles of these components, we contribute to advancing our understanding of the underlying mechanisms and provide valuable insights for optimizing methanol synthesis processes.

Time‐resolved DRIFT Spectroscopy Study of Carbonaceous Intermediates during the Water Gas Shift Reaction over Au/Ceria Catalyst

AbstractChemCatChem homepage for more articles in the collection. The mechanism of the low‐temperature water gas shift reaction (LTWGS) on an Au/CeO2 catalyst was investigated by means of in situ diffuse reflectance infrared (DRIFT) spectroscopy. Under steady‐state LTWGS reaction (373–623 K), the catalyst is partially reduced, and signals from carbonate/formate dominates the infrared spectra. Time‐resolved pulse of CO experiment under a constant partial pressure of water at 423 K indicates that Ce4+ can be reduced to Ce3+ and that formate (HCOO) species cannot be directly related to the CO2 production. Further information was obtained by performing modulation excitation spectroscopy (MES) experiments coupled with a phase‐sensitive detection (PSD) method. Under periodic modulation of the CO partial pressure while keeping the H2O concentration constant, most of the intense bands of carbonate and formate remained constant, indicating that these species are only spectators. The same is observed for the concentration of Ce3+. Conversely, signals in‐phase with the conversion of CO to CO2 are observed and assigned to carboxyl [C(O)OH] and carboxylate (CO2δ−) species, while some monodentate formate (m‐HCOO) also changes but at a lower rate. A plausible associative reaction mechanism where carboxyl/carboxylate are key intermediates is postulated.

Pd/P–CeO2–Al2O3 coatings supported on foam ceramic with controlled morphology for high-performance CO2 methanation

Converting CO2 to highly demanded fuels or chemicals is able to achieve substantial economic and environmental benefits. Herein, a series of Pd/P–CeO2–Al2O3 coatings on foam ceramics with particular morphologies including mesh, rod, plate, as well as mixed mesh and plate, are successfully prepared. The mesh Pd/P–CeO2–Al2O3 coatings (MC) supported on ceramic displayed much higher catalytic activity and better selectivity than those of catalysts with other morphological Pd/P–CeO2–Al2O3 coatings. The CO2 conversion and CH4 selectivity of MC were up to 85.9% and 100%, respectively. The superior catalytic performance was ascribed to the strong MSI effect, high hydrogen storage capacity, abundant oxygen vacancies, and metal sites, as well as moderately basic sites, which were characterized by TEM, XPS, CO2-TPD, and H2-TPD. More importantly, the intermediates and possible reaction pathways were systematically investigated by in situ FTIR. And the high performance of MC mainly comes from the accelerated conversion of carbonate and the hydrogenation of the generated monodentate formate. Overall, the catalytic performance of Pd/P–CeO2–Al2O3 coatings supported on ceramic can be facilely regulated and optimized by accurately devising the morphology of the Pd/P–CeO2–Al2O3 coatings, which offers a novel perspective for high-performance CO2 methanation.

Adjusting active sites and metal-support interactions of ceramic-loaded Pd/P-CeO2-Al2O3 coating to optimize CO2 methanation pathways

Adjusting the active sites and metal-support interactions (MSI) of catalytic coatings on foam ceramics is a desirable strategy to improve CO2 methanation performance. By using a three-dipping and one-roasting technique, a highly active Pd/P-CeO2-Al2O3 catalyst (HA-Pd/PCA) with uniform three-dimensional mesh-like pores and daisy-like clusters was created. As PdO that was embedded in oxygen vacancies of CeO2 was reduced, oxygen vacancies were released. Pd then interacted with lattice oxygen close to the oxygen vacancies to create a strong MSI effect in the form of electron transfer. This translates to better Pd dispersion and more effective activation of the hydrogen. Moreover, the path of the hydrogen spillover that was necessary to hydrogenate the CO2 adsorbed in oxygen vacancies was shortened. In terms of the presence of acid-base sites, oxygen species, and oxygen vacancies, HA-Pd/PCA provided significant advantages. Based on this, the rate of carbonate to formate increased and the conversion pathway changed from a single bidentate formate to a dual pathway comprising bidentate formate and monodentate formate. The consumption and regeneration of hydroxyl groups were kept in balance. The outcomes demonstrated that HA-Pd/PCA had ideal stability, 100 % CH4 selectivity, and 86 % CO2 conversion.

Bifunctionality of Re Supported on TiO2 in Driving Methanol Formation in Low-Temperature CO2 Hydrogenation.

Low temperature and high pressure are thermodynamically more favorable conditions to achieve high conversion and high methanol selectivity in CO2 hydrogenation. However, low-temperature activity is generally very poor due to the sluggish kinetics, and thus, designing highly selective catalysts active below 200 °C is a great challenge in CO2-to-methanol conversion. Recently, Re/TiO2 has been reported as a promising catalyst. We show that Re/TiO2 is indeed more active in continuous and high-pressure (56 and 331 bar) operations at 125-200 °C compared to an industrial Cu/ZnO/Al2O3 catalyst, which suffers from the formation of methyl formate and its decomposition to carbon monoxide. At lower temperatures, precise understanding and control over the active surface intermediates are crucial to boosting conversion kinetics. This work aims at elucidating the nature of active sites and active species by means of in situ/operando X-ray absorption spectroscopy, Raman spectroscopy, ambient-pressure X-ray photoelectron spectroscopy (AP-XPS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Transient operando DRIFTS studies uncover the activation of CO2 to form active formate intermediates leading to methanol formation and also active rhenium carbonyl intermediates leading to methane over cationic Re single atoms characterized by rhenium tricarbonyl complexes. The transient techniques enable us to differentiate the active species from the spectator one on TiO2 support, such as less reactive formate originating from spillover and methoxy from methanol adsorption. The AP-XPS supports the fact that metallic Re species act as H2 activators, leading to H-spillover and importantly to hydrogenation of the active formate intermediate present over cationic Re species. The origin of the unique reactivity of Re/TiO2 was suggested as the coexistence of cationic highly dispersed Re including single atoms, driving the formation of monodentate formate, and metallic Re clusters in the vicinity, activating the hydrogenation of the formate to methanol.

Molecular insights into histidine adsorption on Na-montmorillonite, anatase, and goethite

The adsorption of amino acids (AAs) on minerals plays a role in the geochemical processes that determine the availability of nutrients in the environment. Histidine can be used as typical basic AA because it is frequently detected in natural waters, soils, and sediments. Herein, the pH effects and time factor were analyzed to reveal the molecular-level mechanisms of histidine adsorption on Na-montmorillonite, anatase, and goethite. Attenuated total reflectance Fourier transform infrared (ATR–FTIR) flow-cell measurements, X-ray diffraction (XRD), and density functional theory (DFT) calculations were used to determine the adsorbed species structures and the time-dependent adsorption/desorption processes. The structures of adsorbed histidine were governed by pH conditions, but were not affected by time variations. The histidine adsorbed on the minerals was in the cationic (pH 4), neutral zwitterionic (pH 7.5), and anionic (pH 10.5) forms, which was consistent with those dissolved in solution at the same pH. Adsorption on the clay mineral montmorillonite was favorable due to the dominant interlayer adsorption mechanism at pH 4 and hydrophobic attraction (external basal surface) at pH 4–10.5. Histidine adsorption on the two metal (hydr)oxides was dominated by inner-sphere surface complexation, which involved one or two O atoms of the COO− group. The adsorbed histidine was in the monodentate form on anatase and in the bidentate form on goethite.

The critical role of Ga doped Cu/Al2O3 aerogels in carbon monoxide suppression during steam reforming of methanol

Steam reforming of methanol is an effective method for providing high-purity hydrogen to polymer electrolyte membrane fuel cells, however, this technology still faces the challenge of high CO selectivity. Herein, a series of Ga2O3/Cu/Al2O3 aerogels with different Ga doping (0–50 wt%) were synthesized through freeze-drying assisted sol-gel method. Experimental studies verify that 20GaCuAl exhibits the best performance, which achieves 100% methanol conversion with no CO production. It is demonstrated that Ga doping facilitates the formation of smaller Cu crystalline size, which improves the affinity of catalyst to CO, thus inhibiting CO formation. Results also indicate that the aerogel materials have larger specific surface area and porosity, which is conducive to the homogeneous distribution of the active sites, the intensified diffusion of reactant molecules, and the suppression of their sintering and agglomeration. The methanol reforming performance, especially for CO suppression capability and long-term durability, can be comprehensively promoted, attributing to the synergy of Ga doping and aerogel material fabrication. In situ DRIFTS results illustrate that SRM on Ga2O3/Cu/Al2O3 aerogel undergoes the following process: CH3OH → CH3O* → HCHO→ monodentate HCOOH→ H2 and CO2. The strong absorbed monodentate formate is to the benefit of water-gas shift reaction, thus hindering the generation of CO.

An interactive study of catalyst and mechanism for electrochemical CO2 reduction to formate on Pd surfaces

Electrochemical CO2 reduction reaction to formate (CO2RRTF) on Pd-based surfaces merits very low overpotentials, yet is challenged with identification of a high-performance catalyst and validation of the reaction pathway. In this work, an interactive study of catalyst and mechanism is presented to address the above bottleneck. On one hand, inspired by preliminary mechanistic understanding of HCOOH ↔ CO2 interconversion at Pd surfaces, a Bi-modified Pd/C with the known high performance towards formic acid dehydrogenation (FAD) is elected as the prototype candidate catalyst for CO2RRTF, exhibiting indeed significantly higher activity, selectivity, durability and extended working potentials. On the other hand, the CO2 chemical hydrogenation mechanism is clarified with monodentate formate being the key intermediate for CO2RRTF on Pd surfaces, by applying isotope labeled ATR-SEIRAS measurement and kinetic analysis in conjunction with DFT calculations. The research paradigm facilitates locating efficient catalysts and advancing mechanistic study for CO2RRTF on Pd surfaces and beyond.

Unraveling the role of Co3O4 facet for photothermal catalytic oxidation of methanol via operando spectroscopy and theoretical investigation

Tubular, pie- and bread-shaped forms of Co3O4 with exposed {110}, {112} and {111} facets were prepared and compared in their photothermal catalytic performance and reaction pathways during the oxidation of methanol. Among them, the Co3O4 with exposed {110} facet exhibited the best photothermal catalytic performance (95% methanol conversion, 93% CO2 yield) under solar irradiation, while also maintaining good stability and moisture resistance. Reaction mechanism studies showed that the {110} facets had a strong adsorption capacity for formaldehyde, which facilitated its conversion to formate. The transformation of formaldehyde to formate species was the key step. The key step on the {110} facet was conversion of formaldehyde to a mono-dentate formate species, while conversion on the {112} and {111} facets was mainly to bi-dentate formate species. This study demonstrated that the design of preferential exposed crystal facet can regulate the pathway of photothermal catalytic reaction and realize efficient solar energy utilization.

Mechanism of formic acid oxidation on Bi modified Pt(111): Implication from the concentration effect of formic acid and different coverages of Bi

The concentration dependence of the activity for the formic acid oxidation at pH 1.2 and 4 has been studied on Pt(111) with different coverages of bismuth. The results clearly show: (1) The FAOR on bismuth-modified Pt(111) has no relation with HCOOb adsorbed on platinum but depends on the bismuth coverage. (2) The Tafel slope is ca. 90 - 110 mV in lower potential and increases to nearly the vertical asymptote when the potential increases. (3) Free Pt sites are required for FAOR on bismuth-modified Pt(111). (4) Solution formate, rather than formic acid, is the active species. Combined with previous reports, a kinetic model in which monodentate formate, adsorbed on a Pt-Bi ensemble, is the active intermediate and solution formate is the active species has been proposed. The model is able to reproduce the experimental behavior and agrees with the reaction order measured experimentally. For low potentials, the reaction order for formate is 1, whereas a reaction order of 0.5 is obtained for high potentials.

CeO2-supported Fe, Co and Ni toward CO2 hydrogenation: Tuning catalytic performance via metal-support interaction

The chemical transformation of CO2 produces carbon compounds that can be used as precursors for the production of chemicals and fuels. Here, we investigated the activity and selectivity of the transition metals (Fe, Co, and Ni) supported on CeO2 catalyst for CO2 hydrogenation at atmospheric pressure. We found that Ni/CeO2 shows the highest CO2 conversion compared with Fe/CeO2 and Co/CeO2. Besides, Co/CeO2 and Ni/CeO2 exhibit nearly 100% CH4 selectivity while Fe/CeO2 inclines to produce CO. The characterization results show that the metal-support interaction order is Fe/CeO2 > Co/CeO2 > Ni/CeO2, the weak metal-support interaction over Ni/CeO2 benefits the activation of H2 and then promotes the activity of CO2 hydrogenation. Additionally, in situ DRIFTS results demonstrate that monodentate formate species rather than bidentate formate are the active intermediates. The main route of CO2 hydrogenation to CH4 is that CO2 is firstly transformed to m-HCOO∗ and then direct hydrogenation of the m-HCOO∗ to CH4. This study provides insights into the understanding of the mechanisms of CO2 hydrogenation on CeO2 based catalysts.

Insight into the role of adsorbed formate in the oxidation of formic acid from pH-dependent experiments with Pt single-crystal electrodes

The concentration dependence of the activity for the oxidation of formic acid at pH 1.2, 2.4, and 3.9 has been studied on Pt(1 1 1), Pt(1 0 0), and stepped Pt[n(1 1 1) × (1 1 0)] electrodes. The results clearly demonstrate that, in this pH range, formate, and not formic acid, is the active species. To analyse the data, a kinetic model in which adsorbed monodentate formate is the active intermediate has been proposed. On Pt(1 1 1), a steady increase in the reaction rate with increasing pH and a reaction order of 1 for the bulk formate concentration was obtained, in agreement with the proposed model. On the other hand, the competition between adsorbed hydrogen and formate for the adsorption sites on Pt(1 0 0) cancels both the concentration and the pH dependence of the reaction rate. On this electrode, the potential dependence of the reaction rate for the dehydrogenation of formic acid to COad was also studied and found to go through a maximum both at pH 1.2 and at pH 3.9, although the rate of dehydrogenation is slower and the maximum is broader at pH 3.9. The slower rate at the higher pH is consistent with the well-known fact that dehydrogenation of HCOOH is an acid-catalysed reaction. On Pt[n(1 1 1) × (1 1 0)] electrodes the behaviour observed is similar to that of Pt(1 1 1), with a reaction order of 1 for formate. The only significant difference with respect to the Pt(1 1 1) surface is the formation of COad due to the presence of (1 1 0) steps.