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The present study investigates synthesis, characterization, and application of TiO2 supported Keggin phosphotungstic acid in biorenewable transformations. In particular, 10 wt%, 20 wt%, 30 wt% and 40 wt% Keggin phosphotungstic acid was loaded over TiO2 support via wet impregnation method to prepare EPTN-1, EPTN-2, EPTN-3, and EPTN-4 catalysts, respectively. After this, synthesized catalysts were tested in a microwave reactor to measure reactivity trend in order HPW > EPTN-4 > EPTN-3 > EPTN-2 > EPTN-1. A maximum 95% levulinic acid (LA) conversion was measured in the presence of 72 mg EPTN-4 catalyst, two mmol LA in 1:42 LA: EtOH (ethanol) molar ratio at 393 K in 120 min at a stirring speed of 300 rpm. No significant loss in heterogenized EPTN-4 catalyst was measured after five application cycles. A detailed characterization of synthesized catalyst showed that the Keggin structure remained intact after heterogenization.

The π-binding mode of Rh80O120 rather than a stronger σ-binding mode of Rh2O3 (100) surface to CC, reflects the superior catalytic activity of Rh2O3 sub-nanoparticles confined in SiO2 towards ethylenic hydroamination, in contrast to large particle.

The catalysts derived from Co/Fe nanoparticles display promising activity toward electrochemical reactions. The electrochemical activity of these nanoparticles could be directly correlated to their surface electronic properties.

Pd-doped chabazite (Pd/CHA) offers unique opportunities to adsorb and desorb NOx in the target temperature range for application as a passive NOx adsorber (PNA). The ability of Pd/CHA to trap NOx emissions at low temperatures (

We report the electrochemical investigation of 5% Al doped MoS$_2$@rGO composite as a high-performance anode for sodium (Na)-ion batteries. The x-ray diffraction (XRD), Raman spectroscopy and high-resolution transmission electron microscopy characterizations reveal that the Al doping increase the interlayer spacing of (002) plane of MoS$_2$ nanosheets and form a stable 1T phase. The galvanostatic charge-discharge measurements show the specific capacity stable around 450, 400, 350, 300 and 200 mAhg$^{-1}$ at current densities of 0.05, 0.1, 0.3, 0.5 and 1~Ag$^{-1}$, respectively. Also, we observe the capacity retentions of 86% and 66% at 0.1 and 0.3 Ag$^{-1}$, respectively, over 200 cycles with a consistent Coulombic efficiency of nearly 100%. The cyclic voltammetry, galvanostatic intermittent titration technique, and electrochemical impedance spectroscopy are used to find the kinetic behavior and the obtained value of diffusion coefficient falls in the range of 10$^{-10}$ to 10$^{-12}$ cm$^2$s$^{-1}$. Intriguingly, the in-situ EIS also explains the electrochemical kinetics of the electrode at different charge-discharge states with the variation of charge transfer resistance. Moreover, the post cycling investigation using ex-situ XRD and photoemission spectroscopy indicate the coexistence of 1T/2H phase and field-emission scanning electron microscopy confirm the stable morphology after 500 cycles. Also, the Na-ion transport properties are calculated for 1T Al--MoS$_2$@rGO interface and Al--MoS$_2$--MoS$_2$ interlayer host structure by theoretical calculations using density functional theory.

Density functional theory (DFT) simulations are conducted to understand the differentiation of activity and selectivity trends between primary and secondary alcohols towards the non-oxidative dehydrogenation (NODH) reaction. Propanol and isopropanol are employed as model molecules to explore the NODH on the (111) facets of Cu. The initial dehydrogenation of propanol via the hydroxyl route exhibits a higher barrier (96.8 kJ/mol) as compared to that of isopropanol (61.4 kJ/mol). Furthermore, the second dehydrogenation step resulting in the formation of the carbonyl compound is also calculated to show higher barrier of primary alcohol (83 kJ/mol) than secondary alcohol (51.3 kJ/mol). Overall, for the consecutive dehydrogenation steps, propanol is observed to show higher activation barriers as opposed to that of isopropanol, indicating towards a higher conversion rate for isopropanol, similar to the trend observed experimentally. However, the subsequent dehydrogenation of the carbonyl compound formed shows a barrier of 112.8 kJ/mol for acetone and that of 70.6 kJ/mol for acetaldehyde owing to the higher stability of ketone. The formation of ester from the propionyl produced upon acetaldehyde dehydrogenation is calculated to show the lowest barrier (64.6 kJ/mol) amongst the dehydrogenation steps of primary alcohol dehydrogenation route, suggesting towards lower selectivity in case of NODH of propanol.

Periodic density functional theory (DFT) calculations are employed to understand the origin of structure sensitivity in hydrodechlorination (HDC) of trichloroethylene (TCE) over different facets of a palladium catalyst. The HDC reaction is simulated on the terrace (Pd (111) and Pd (100)) and undercoordinated (Pd (211) and Pd (110)) sites of the Pd catalyst. The most stable binding configuration of TCE on the Pd surfaces is observed to be through the di-σ mode of binding, wherein each carbon atom of the TCE molecule is adsorbed atop of the Pd atom. On comparing TCE adsorption over different facets of Pd, a maximum binding energy of −178 kJ mol−1 is calculated over the Pd (110) surface. TCE, upon adsorption on Pd catalyst, undergoes dechlorination followed by hydrogenation of the hydrocarbon intermediates. The activation energies for C–Cl bond dissociation steps are significantly low when compared to the hydrogenation steps. The chlorine released from dechlorination tends to block the active sites, thereby poisoning the surface with high binding energies (B.E > −160 kJ mol−1) on all the surfaces. The trend in chlorine binding energies on Pd facets follows: Pd (110) > Pd (211) > Pd (100) > Pd (111). The removal of surface chlorine is facilitated by its reaction with surface hydrogen to form hydrogen chloride. The activation energy for hydrogen chloride formation is calculated to be 90 kJ mol−1 and 88 kJ mol−1 on Pd (111) and Pd (100) terrace sites, respectively and 109 kJ mol−1 and 118 kJ mol−1 on the step Pd (211) and corrugated Pd (110) facets, respectively. This suggests the ease of removal of Cl as HCl from the terrace sites as compared to the step and corrugated sites. The structure sensitivity in the TCE HDC reaction could possibly arise due to the differences in the energetics of Cl removal on different Pd facets. This mechanistic understanding could provide a rationale for designing suitable catalysts for the HDC of TCE.

An ab initio microkinetic model (MKM) is developed to understand the reactivity trends of the terrace (111) and step (211) sites of transition metal catalysts for biogas reforming (BGR) to produce syngas. Over the (111) sites, Ni, Rh and Pd show high turnovers for CH4 consumption (>1 s−1), however, with enhanced coke formation (>0.1 s−1). In comparison, Co and Ru exhibit reduced coke formation rates ( 1 s−1) via methane dissociation. Here also on the (211) surface, Ru shows significantly reduced coke formation rates (0.1 s−1).

C-H bond activation steps in non-oxidative methane dehydroaromatization (MDA), constitute a key functionalization of the reactant and adsorbed species to form aromatics. Previous studies have focused on studying the energetics of these steps at the most stable active sites involving molybdenum carbide species. Herein, a different paradigm is presented via studying the reactivity of a metastable molybdenum carbide (Mo2C6) nanocluster for the C-H bond activation of methane, ethane, and ethylene and comparing it with the reactivity of the lowest energy Mo2C6 nanocluster. Interestingly, the metastable nanocluster is observed to result in a consistent reduction (by half) in the C-H bond activation barrier of the respective alkane and alkene molecules compared to the global minimum isomer. This specific metastable form of the nanocluster is identified from a cascade genetic algorithm search, which facilitated a rigorous scan of the potential energy surface. We attribute this significant lowering of the C-H bond activation barrier to unique co-planar orbital overlap between the reactant molecule and active centers on the metastable nanocluster. Based on geometrical and orbital analysis of the transition states arising during the C-H bond activation of methane, ethane, and ethylene, a proton-coupled electron transfer mechanism is proposed that facilitated C-H bond cleavage. Motivated by the high reactivity for C-H bond activation observed on the metastable species, a contrasting framework to analyze the elementary-step rate contributions is presented. This is based on the statistical ensemble analysis of nanocluster isomers, where the calculated rates on respective isomers are normalized with respect to the Boltzmann probability distribution. From this framework, the metastable isomer is observed to provide significant contributions to the ensemble average representations of the rate constants calculated for C-H bond activation during the MDA reaction.

Reactivity trends of transition metal catalysts are studied for the ethane dehydrogenation reaction using CO2 as a mild oxidant. An ab initio microkinetic model (MKM) is constructed to gain insights about the dominant route for CO2 reduction and simultaneous ethylene formation over the terrace (111) and step (211) surfaces of the catalysts. At the terrace sites, Rh and Pt are observed to show high ethane consumption with maximum turnovers to produce ethylene. For CO2 consumption, Rh, Ru, Ni and Co are calculated to exhibit significant activity (TOF ∼1 s−1). CO2 on the (111) surface is predominantly reduced through the reverse water gas shift (RWGS) reaction, since the production rates of H2O and CO are comparable to the consumption rates of CO2. At the step sites, the hydrogenolysis reaction is more pronounced leading to coke formation. Hydrogenolysis at the step surface also led to significant activity for the reforming reaction. Over the (211) surface, the direct dehydrogenation of ethane to produce ethylene is observed to be predominant. For oxygen assisted ethane dehydrogenation, Co, Ru, Ni and Rh are calculated to show appreciable activity (>1 s−1). The same four metals also show significant CO2 consumption at the step surface. The MKM is further utilised to design bimetallic alloys of Ni and Pt to achieve greater CO2 consumption activity and reduced coke formation with significant activity for the dehydrogenation reaction. While most of the alloys undergo reforming and RWGS reactions, three potential bimetallic combinations (NiFe, NiCo and PtCo) are selected, exhibiting appreciable activity for CO2 assisted dehydrogenation of ethane with some reduction in coke formation, compared to their monometallic counterparts.

Sodium ion batteries have shown their potential as an attractive candidate for energy storage. Different metal oxides, especially transition metal oxides such as V4O10 have shown good electrochemical characteristics owing to their unique lattice structure and multiple oxidation states. An understanding of the sodium-ion transport is crucial in optimizing these electrode materials. Here, the trends in sodium-ion diffusivity are estimated using atomistic modeling. Na-ion diffusivity is calculated using molecular dynamics (MD) simulations in NaxV4O10 for different sodium contents (0.33

Dense thin-film electrodes of Ce0.9Pr0.1O1.95 (PDC) are tested for CO2 reduction in a solid oxide electrolysis cell (SOEC) with yttria-stabilized-zirconia (YSZ) electrolyte and La0.8Sr0.2MnO3-δ (LSM) air electrode. A spray pyrolysis technique is utilized to fabricate thin-film electrodes of PDC with an approximate thickness of 400 nm. Dense microstructure in the thin film is fabricated to understand the relative role and limitations offered by surface reaction and oxygen anion diffusion within the bulk of the PDC electrodes while disallowing any gas phase diffusion. Electrochemical tests are performed in a geometrically well-defined cell to ascertain the operating mechanism. Electrochemical reduction of CO2 is carried out in the SOEC mode on the PDC electrode. Cu is added to the surface of the dense thin film of PDC. Polarization resistance of the thin-film electrode measured at the open-circuit voltage, in an H2/CO2 (8% H2) environment, is observed to reduce by 45% on adding Cu at the surface of the electrode. This suggested that the electrocatalytic activity of the thin-film electrode is limited by sluggish surface activity, which is improved on adding the surface with Cu.

Effect of framework Bronsted Acidity by varying SiO2/Al2O3 ratio (SAR) of HMCM-22 zeolite is studied with respect to the formation of active molybdenum carbide and its anchoring over zeolite (HMCM-22) channels of Mo/HMCM-22 catalyst tested for methane dehydroaromatization (MDA) reaction. For this purpose, HMCM-22 is synthesized by conventional methods with varying SAR (30, 40 & 55) and is studied for MDA reaction with 5 wt% Mo loading. XRD, BET, NH3-TPD, H2-TPR, 27Al MAS NMR, Raman spectroscopy and XPS techniques are used to characterize 5Mo/HMCM-22 catalyst having different SAR. XPS analysis of carburized 5Mo/HMCM-22 (SAR-30, 40 & 55) catalyst confirms that higher content of molybdenum carbide (Mo2C) forms over HMCM-22 channels at SAR-30 as compared to SAR-40 and SAR-55 due to effective binding of initial MoOx species. Interaction of initial MoOx species with HMCM-22 zeolite framework is analyzed using 27Al MAS NMR and Raman spectroscopic studies which confirm that MoOx species bind differently at SAR-30, 40 and 55 which affects the catalytic performance. Lower reducibility of MoOx species at SAR-30 confirms that MoOx species strongly interact with HMCM-22 channels at SAR-30 as confirmed by H2-TPR study. Maximum transformation of MoOx species into active molybdenum carbide over HMCM-22 at lower SAR (30) during carburization results in higher activity of 5Mo/HMCM-22 (SAR-30) catalyst with lower coke content.

The present work introduces the favorable synthesis of porous functionalized nanomaterials with excellent surface area, porosity, and high CO2 capture ability to facilitate cyclizative reactions by...

Acetate is emerging as a promising feedstock for biorefineries as it can serve as an alternate carbon source for microbial cell factories. In this study, we expressed acetyl-CoA synthase in

The last few decades witnessed a remarkable advancement in the field of molecular anion receptors. A variety of anion binding motifs have been discovered, and large number of designer molecular anion receptors with high selectivity are being reported. However, anion detection in an aqueous medium is still a formidable challenge as evident from only a miniscule of synthetic systems available in the literature. We, herein, report 5,5'-dithio-bis(2-nitrobenzoic acid) (Ellman's reagent) appended with amino acids as supersensitive anion sensors that can detect F

Bio-oil obtained from the pyrolysis of waste biomass is a potential alternative to fossil fuels. However, the presence of high oxygen content makes it unsuitable for direct use as a fuel, and therefore, upgradation of bio-oil is required. The catalytic hydrodeoxygenation (HDO) has been widely used for the upgradation of bio-oil to transportation fuels and value-added chemicals. However, since bio-oil is a complex mixture of different compounds, the exact mechanism for the bio-oil HDO is unknown. Phenolics, such as m-cresol, guaiacol, phenol, anisole, etc., derived from lignin pyrolysis, have been widely studied as model compounds to understand the HDO pathway of bio-oil. The activity and selectivity of these reactions are governed by different catalytic parameters, such as type of metal and support, nature of active sites, size of the catalyst, etc. The effect of these parameters on the selective production of aromatics and cyclic hydrocarbons through HDO of phenolics is briefly discussed in this chapter. In order to develop an efficient catalyst for the HDO reactions metal functionality, the optimum ratio of acid sites and acidity of the support should be taken into consideration.

Tremendous efforts are put forth for the development of biological processes for fuels, chemicals, and other intermediates, replacing the classical or traditional fossil-based processes. For several years, ethanol is the major product of renewable substrates, but the process is not economical as it requires pretreatment of substrates. Lignocellulosic biomass (LCB), the most abundant renewable substrate, is recalcitrant and series of treatments like acid/alkali pretreatment and enzymatic hydrolysis are required for the release of fermentable sugars, no natural microorganisms can utilize the native biomass and produce value-added products. Therefore various strategies with the screening of new microbes, strain engineering, and process optimization are promising to construct microorganisms with all the necessary functions and highly resistant to the inhibitors. Another approach to increasing the credibility and economic viability of the process is the conversion of LCB to high value-added products like organic acids and diols. In this chapter, we compare the processes developed for various organic acids and diols (drop-in chemicals) using LCB, and later we provided the applications of various platform and drop-in chemicals in the polymer and chemical industry.

The dehydroaromatization (DHA) reaction of methane under non-oxidative conditions is carried out over a molybdenum catalyst supported on HZSM-5 and boric acid (BA) treated HZSM-5 at 700 °C and atmospheric pressure. As compared to the conventional Mo/HZSM-5 catalyst, wherein a maximum of 100 nmol gcat−1 s−1 of benzene is measured, BA treated Mo/HZSM-5 exhibited a significantly high benzene formation rate (∼420 nmol gcat−1 s−1) at around 90 minutes time on stream. In addition, a boron treated catalyst was measured to have an 8 wt% reduction in coke formation as compared to the untreated catalyst. One prevailing thought for improved activity is ascribed to the desired moderation of Bronsted acid sites on BA treatment. This is probed by temperature programmed desorption (TPD) experiments which indicated an overall reduction in Bronsted acidity on BA treatment of the catalyst. Quantum mechanical density functional theory (DFT) calculations further estimated a high deprotonation energy (DPE) of the Bronsted acidic proton anchored on the boron substituted site (DPE = 1145.4 kJ mol−1) as compared to the Al site (DPE = 1100.6 kJ mol−1) of the zeolite framework, suggesting a reduction in Bronsted acidity. FTIR and 11B MAS NMR spectra confirmed the presence of trigonal boron species substituted in the zeolite framework. In addition, the molybdenum oxide (Mo6+) species, which is known to act as the precursor for active sites in methane DHA, is observed to form in a relatively greater quantity on the boron treated catalyst in the temperature program reduction (TPR) study of the calcined catalysts. Thus, BA treatment moderates the acidity of the Mo/HZSM-5 catalyst to provide the desired active sites for high reactivity.

Owing to its low boiling point, tetrahydrofuran (THF) is an economical choice of solvent in biorenewables processing. Multifold acceleration in reaction rates is experimentally observed for Bronsted acid catalyzed reactions in THF, as compared to that in water. Herein, utilizing ab initio Car–Parrinello molecular dynamics (CPMD), classical molecular dynamics (MD) and density functional theory (DFT) simulations, a systematic theoretical framework is presented to explain the significant differences in the reactivity of Bronsted acid protons in THF as compared to that in water. The probe reaction of choice is the dehydration of 4-hydroxy-6-methyl lactone (HML) obtained from a biomass-derived substrate. Classical MD simulations elucidate the hydrogen bonding networks formed around the hydroxyl group of the reactant HML in explicit solvation environments of water and THF. The activation free energy barrier for the water removal step is calculated using CPMD–metadynamics simulations. In THF, the free energy barrier is 107 kJ mol−1, which is observed to be lower by 26 kJ mol−1 as compared to that in water. This significant difference in activation free energies for the dehydration step explains the difference in reactivity. Static DFT simulations further elaborated the effect of the first solvation shell around the hydroxyl substituent on describing the activation barriers of the dehydration reaction. While the solvent environment in DFT simulations is kept implicit in nature, few explicit molecules of THF and water are allowed to interact with the hydroxyl group and β-carbon of HML. The activation energy for the dehydration of HML is calculated to be 103 kJ mol−1 in the pure water environment. Akin to the difference in free energy barriers obtained from CPMD calculations, the activation energy calculated from DFT is observed to be 25 kJ mol−1 lower in THF as compared to that in water.

The advent of machine learning (ML) techniques in solving problems related to materials science and chemical engineering is driving expectations to give faster predictions of material properties. For heterogeneous catalysis applications, relying on the age-old Sabatier principle, an ab initio in silico high throughput screening of catalyst materials is envisaged, wherein ML based methods show potential to significantly reduce the experimental as well as computation cost. The availability of ML algorithms (in open source libraries like Scikit-Learn) and materials database (like CatApp and Materials Project) further augments this realization. By using these resources, ML models are developed to predict the binding energies of oxygen and carbon on bimetallic alloys and Cu-based single atom alloys (SAAs) using the features of metals that are readily available in the periodic table. Several ML models for predicting oxygen binding energy for AA terminated A3B alloys are analysed and gradient boosting regression (GBR) is observed to give superior performance with a root mean square error of 0.31 eV in the test. In addition, GBR based ML models are demonstrated to predict the oxygen and carbon binding energies of AB terminated A3B alloys with a test error of 0.38 eV and 0.35 eV respectively. The binding energy of oxygen and carbon on Cu-based SAAs is predicted with a test error of 0.36 eV and 0.37 eV respectively. Moreover, the computational time for predicting the binding energy using ML is 0.0006 s on a dual-core laptop which is significantly less than the time required for DFT calculations. DFT and ML calculated carbon and oxygen binding energies for the bimetallic A3B alloys are further used in an ab initio microkinetic model to calculate the turn over frequency (TOF) for ethanol decomposition and non-oxidative dehydrogenation reactions. The TOFs over bimetallic alloys obtained using the ML calculated binding energies follow the same trend as that obtained using the DFT energies, with the TOF values being the same or within an order of magnitude range. This shows that catalyst screening using binding energy as a descriptor can be performed using ML models, bypassing time and resources consuming DFT calculations. This is likely to speed up the process of novel catalyst discovery.

Product selectivity in aqueous phase phenol hydrogenation on well-defined supported Pd nanostructures (spheres, cubes, and octahedra) was studied using defined experiments and density functional th...

Oxygen reduction reaction in a double perovskite material, PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF), was studied for application as a cathode in a solid oxide fuel cell (SOFC). Electrochemical measuremen...

Technologies for the processing of lignocellulosic biomass into fuels and chemicals are generally focused on selective chemical transformation of the three different types of constituents: cellulose, hemicellulose and lignin. In this regard, heterogeneous catalytic reactions are employed to defunctionalize and upgrade the platform molecules obtained selectively from these constituents. Herein, a selection of studies are discussed which are adapted to deoxygenate and valorize the biomass-derived platform molecules with a specific focus on understanding the reaction mechanisms and rational design of a heterogeneous catalyst. The selection of the deoxygenation process constituted a combination of two or three reactions. For example, ring-opening reactions of the cyclic compounds are studied with decarboxylation, dehydration, hydrogenation and/or Diels–Alder reaction carried out on metal, acid and/or oxide catalysts. The platform molecules studied here include an array of saturated lactones, 2-pyrones, cyclic...

The effects of microwave and nonmicrowave heating methods on the synthesis of ethyl levulinate (EL) from levulinic acid (LA) have been investigated in the present study. The levulinic acid esterification experiments were performed in the presence of silicotungstic acid catalyst and ethanol in a microwave and nonmicrowave instant heating reactor. An experimental fit of experimental data in a kinetic model suggested that LA esterification follows a pseudo-first-order reaction mechanism. Consequently, activation barriers were calculated (44–45 kJ/mol) and a negligible difference was found for LA esterification reaction performed in both the reactors. Nevertheless, slightly higher LA conversions were measured under microwave irradiations as compared to experiments performed in a nonmicrowave instant heating reactor. Thus, series of experiments were performed to study the (i) nonthermal and (ii) thermal effects of microwave heating irradiations. Eventually, it was found that the enhanced LA conversion in micro...

The promotional role of Zn in hydrodeoxygenation (HDO) reactions of 5-hydroxymethyl furfural (HMF) to produce 2,5-dimethyl furan (DMF) over the Pd catalyst was studied using plane-wave density functional theory (DFT) calculations. HMF is first hydrogenated to form bis(hydroxymethyl) furan (BHMF), which undergoes HDO to form DMF. In order to provide a mechanistic explanation to the experimental observation, DFT calculations focusing on the energetics of the HDO reaction steps for BHMF conversion to DMF were performed on three different surfaces: Pd(111), Pd(211), and PdZn(211). Zn was assumed to preferentially substitute the defect sites of the bimetallic catalyst in reduced metallic state. Calculated values of activation energies for C–O dissociations steps were significantly reduced on the PdZn(211) surface, compared to the Pd(111) and Pd(211) surfaces. Therefore, theoretical results provided a clue to the reactivity of the Zn-decorated step sites for the HDO reaction.

Ab initio microkinetic modeling was performed to study ethanol conversion to acetaldehyde on Pt-based bimetallic alloys in a non-oxidative environment. Alloying Pt with Au, Ag, Cu, Co, Ni, Zn, Cd, Al, Ga, In, Tl, Ge, Sn, Pb, As, and Sb showed an increase in product turnover by at least an order of magnitude compared with Pt at 423 K. This was correlated to the increased stabilization of CH3CH0 species over these alloys. Among the alloy candidates; Pt3Cu, Pt3Zn, Pt3Ga, Pt3Ge, Pt3Sb, and Pt3Pb were found to be more active than Pt.

Molecular dynamics simulations were utilized to determine the oxygen anion diffusivity in pure ceria (CeO2) and doped ceria MxCe1-xO2-0.5x (M=Gd, Sm and Pr) with varying level of dopant concentration from 5–30% (x = 0.05–0.3). Doping with Gd showed an improvement in oxygen anion diffusivity value by two order of magnitude (D = 4.67x10−8 cm2/s at 1173 K) as compared to the undoped ceria (D = 1.33x10−10 cm2/s at 1173 K). 10% of doping level was estimated as the optimum concentration of all the dopants at which all of the doped ceria materials showed maximum diffusivity of oxygen anion. Among the three dopants studied, Pr was observed to show maximum diffusivity of oxygen anion in the temperature range of 773–1173 K of simulations.

Electrochemical reduction of CO2 is performed in a solid oxide electrolysis cell (SOEC), with Cu-Pr0.1Ce0.9O2-δ (Cu-PDC) composite cathode and La0.8Sr0.2MnO3-δ (LSM) anode on yttria-stabilized zirconia (YSZ) electrolyte. The electrochemical performance of the fabricated SOEC for CO2 reduction is compared with a similar high-temperature SOEC having Cu-infiltrated praseodymium-doped ceria electrode (Neetu et al., ECS Transaction 78, 3329, 2017). On varying the applied potentials and reducing environment at different volumetric ratio of CO2/CO and CO2/H2, electrochemical measurements are carried out to understand the role of reducing atmosphere. On the Cu-PDC composite electrode, a significantly improved reduction current (− 0.84 A cm−2 at Vapp = 2.5 V) is measured as compared to the Cu-infiltrated electrode reported earlier. Oxygen vacancy formation energy on doped ceria surface is calculated, using density functional theory, and found to be relatively lower (∆Evac = 84.6 kJ mole−1) as compared to the un-doped ceria surface (∆Evac = 152.8 kJ mole−1), indicating facile oxygen anion transport in Cu-PDC. Density of state calculations shows Pr substitution in ceria responsible for the reduction in band gap [O(2p) → Ce(4f)] from 1.75 to 0.4 eV, contributing to electronic conduction. The theoretical results thus elucidate the activity of Pr-doped ceria materials for CO2 reduction to CO. The theoretical results combined with experiments conducted on Cu-PDC electrode are therefore expected to provide a basis for the development of a new electrocatalyst for CO2 reduction.