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In this study, red mud (RM), an industrial waste, was used as a raw material to prepare a novel red mud-based Co3O4–Fe2O3–Co2AlO4 (Co–Fe/RM) catalyst using a simple solid-phase method, and lomefloxacin hydrochloride (LOMH) was degraded by using Co–Fe/RM to activate peroxymonosulfate (PMS). The optimum preparation conditions of the mass ratio of Co(NO3)2·6H2O to RM, calcination temperature and calcination time were 1.5 : 1 (1.5 g of Co(NO3)2·6H2O and 1 g of RM), 700 °C, and 2 h, respectively. The characterization results showed that Fe2O3, Co3O4 and Co2AlO4 were the main active components in Co–Fe/RM, and Co–Fe/RM could expose more reaction sites compared with RM. The Co–O–Al bonds that existed on the Co–Fe/RM could facilitate the redox cycle between Co(II) and Co(III), thus improving the Co–Fe/RM catalytic activity. For 10 mg L−1 LOMH solution with a volume of 100 mL, the maximal removal ratio of LOMH (89.3%) was obtained at 20 min under the optimal parameters (0.3 g L−1 Co–Fe/RM dosage, 1 mmol L−1 PMS concentration, initial pH 5.5, and 30 °C of reaction temperature) in a Co–Fe/RM/PMS system. The trapping experiments proved that SO4˙−, 1O2 and O2˙− dominated the degradation of LOMH, and a possible catalytic mechanism of activating PMS using the prepared catalysts was proposed. For LOMH in the Co–Fe/RM/PMS system, degradation pathways were analyzed via density functional theory (DFT) calculations and liquid chromatography–mass spectrometry (LC–MS). A toxicity estimation software tool (TEST) and the Chlorella pyrenoidosa cultivation experiment were used to evaluate the biological toxicity of the treated LOMH solution. The recycling experiments found that the Co–Fe/RM had distinguished reusability and excellent stability. The mineralization assessment showed that organic carbon contents could be effectively diminished in the treated LOMH solution. This study provided a viable way for the beneficial use of RM to activate PMS and offered a low-cost and efficient catalyst for the degradation of pollutants in wastewater. [ABSTRACT FROM AUTHOR]

The catalytic efficiency of CeO2 in soot oxidation was significantly affected by its grain morphology and calcination temperature. Nanocube-shaped and nanorod-shaped CeO2 catalysts were synthesized via a hydrothermal method with different calcination temperatures. Activity tests revealed that the nanorod-shaped CeO2 exhibited superior catalytic activity compared to the nanocube-shaped catalysts at equivalent calcination temperatures. Furthermore, an inverse relationship between the catalytic activity and the calcination temperature was observed in the nanorod-shaped CeO2 catalysts, with those calcined at 300 °C exhibiting the most effective low-temperature catalytic performance. Combined characterization techniques and density functional theory calculations showed that the improved catalytic performance can be attributed to the increased abundance of oxygen vacancies, enhanced lattice oxygen mobility and higher surface energy due to their unique surface defect structure and electronic structural feature, in addition to the reduction in grain size. [ABSTRACT FROM AUTHOR]

Focusing on renewable energy, we developed an efficient and robust catalyst for overall water splitting (OWS). Using density functional theory (DFT) as the guide, a combination electrode with bifunctional activities based on Co-based carbonate hydroxides (CCHs) and pyrenely-graphdiyne nanowalls (Pyr-GDY-NWs) with three-dimensional structures was designed, and then a series of experiments were attempted to prepare the combination electrode CCH@Pyr-GDY-NWs. From the data of theory and experiment, we found that the combination electrode CCH@Pyr-GDY-NWs exhibits an outstanding catalytic activity towards OWS. The design approach reported herein could open up a new avenue for the construction of three-dimensional Pyr-GDY-NW-based electrodes with high catalytic activity. [ABSTRACT FROM AUTHOR]

A series of reusable polystyrene-supported imidazolium acidic ionic liquid catalysts were synthesized to replace industrial sulfuric acid for the synthesis of bisphenol compounds. These ionic liquids were covalently bonded to the support, reaching a high loading of 1.62–1.80 mmol g−1, respectively. As expected, they achieved a catalytic effect comparable to that of sulfuric acid in the condensation reaction of 9-fluorenone with phenol. Under the optimum reaction parameters, a high yield and high selectivity of 99.9% and 99.7% were achieved for 9,9-bis(4-hydroxyphenyl)fluorene (BHPF). Moreover, this catalyst was also employed for synthesizing other bisphenol compounds and 99.0% conversion of the substrate was achieved. Based on the experimental results and density functional theory (DFT) calculations, a possible reaction mechanism was proposed, which indicated that 9-fluorenone and phenol were simultaneously activated through the synergistic catalysis of anions and cations in a polystyrene-supported ionic liquid catalyst. The recycling experiment results suggested that [PS-PsIm][CF3SO3] maintained a high catalytic activity in five reaction runs, making this a promising catalyst for the synthesis of bisphenol compounds. [ABSTRACT FROM AUTHOR]

The mechanisms of Cu(II)/DBU-catalyzed carboxylation of homopropargylic amines with CO2 to construct 6-methylene-1,3-oxazin-2-ones are studied via density functional theory. The calculations suggest that Cu(II) catalysts exhibit a positive effect on the process of intramolecular cyclization, and the catalytic activities of which are determined by their coordination abilities ((DBU)CuCl2 < CuCl2 < [(DBU)CuCl]+). Furthermore, three roles of DBU are revealed in this study: (a) DBU acts as the proton-acceptor to capture a proton of homopropargylic amines. (b) DBU attacks CO2 to form DBU-CO2 as the nucleophilic agent, and then DBU-CO2 assists the H+ shift as the proton shuttle. (c) DBU serves as the ligand replacing one Cl− anion of CuCl2, forming the activated species [(DBU)CuCl]+. Besides, the theoretical study well explains the selectivity of Cu(II)-catalyzed reactions (6- vs. 7-membered cyclization), and the 6-membered products are found to be formed selectively. Overall, our work reproduces the experimental results well and provides an indispensable understanding of CO2-conversion to synthesize various high-value chemicals with the assistance of a catalytic system combining transition-metal catalysts and organic bases. [ABSTRACT FROM AUTHOR]

The development of substantial, environment-friendly and low-cost electrocatalysts for an efficient oxygen reduction reaction (ORR) is essentially important for the production and storage of green energy which has sparked the curiosity of researchers for scalable production of metal-free electrocatalysts from biowaste. We report an easy transformation of chestnut-derived biowaste into reduced graphene oxide (rGO) and pyridinic-N-dominated nitrogen-doped rGO (NCS-rGO). The synthesized catalyst exhibits better ORR activity with an onset and half-wave potential of 0.93 V and 0.86 V, respectively, along with a high diffusion-limiting current density of 5.05 mA cm−2. Under alkaline conditions, we found that NCS-rGO shows an unusually high electrocatalytic activity that is superior to that of the commercial 20% Pt/C catalyst. More notably, the NCS-rGO-based ORR electrocatalyst manifests higher methanol tolerance, without deterioration in catalytic activity even in the presence of significant amount of methanol, outperforming the current state-of-the-art Pt electrocatalyst. Density functional theory (DFT) studies illustrate that pyridinic N is a decisive part of NCS-rGO to achieve the best ORR performance. [ABSTRACT FROM AUTHOR]

Dimethyldichlorosilane, which is the most important organic silicon monomer, can be prepared using a novel core–shell catalyst. However, the debate continues regarding its redistribution mechanism. In the current study, the redistribution mechanism catalyzed by the ZSM-5(5T)@MIL-53(Al) catalyst was theoretically studied via density functional theory on the level of M06-2X/def2-TZVP. Then, the catalytic performances of different active centers modified with AlCl3 were evaluated. The results showed that the active center of the former was Brønsted acid, while that of the latter modified by AlCl3 was Lewis acid. In addition, Lewis acid increased the catalytic activity in comparison with Brønsted acid. The calculations of activation energy, frequency vibrational analysis, bond order analysis, frontier molecular orbital theory, electronic localization function, and localized orbital locator analyses were in agreement with the said mechanism and results. [ABSTRACT FROM AUTHOR]

Producing molecular hydrogen (H2) using water provides a sustainable approach for developing clean energy technologies. Herein, we report highly active ruthenium (Ru) clusters supported on iron oxide (Ru/Fe3O4) and Fe3O4/multi-walled carbon nanotubes (Ru/Fe3O4/MWCNTs) by simple electrochemical deposition in a neutral aqueous medium. The supported catalyst exhibits good hydrogen evolution reaction (HER) activity in an acidic environment. Cyclic voltammograms (CVs) of potassium ferrocyanide (K4[Fe(CN)6]) confirm that MWCNTs enhance the electron transfer process by decreasing the redox formal potential. The overpotentials of Ru/Fe3O4/MWCNTs and Ru/Fe3O4 electrocatalysts versus the reversible hydrogen electrode (RHE) were found to be 101 mV and 306 mV to reach a current density of 10 mA cm−2. As prepared, the catalyst displays good stability and retain its HER activity even after 1000 cycles. Furthermore, the stability of Ru/Fe3O4/MWCNTs was studied using the chronopotentiometric (CP) technique for 12 h and found negligible loss in the catalytic activity towards the HER. To explore the role of Ru and underneath MWCNTs in improving the catalytic performance of Fe3O4, density functional theory (DFT) calculations were carried out. DFT calculations indicate that the octahedral site of Ru/Fe3O4 favors the HER with a low overpotential. However, Ru/Fe3O4/MWCNTs are more efficient towards the HER, which could be due to the availability of both octahedral and tetrahedral catalytic sites. [ABSTRACT FROM AUTHOR]

The removal of sulfur in diesel fuel requires efficient hydrodesulfurization catalysts during the upgrading process. However, although the traditionally prepared CoMoS catalyst is effective for hydrodesulfurization, it often is associated with problems such as a poor activity and deactivation susceptibility at high temperatures. In this work, chemical exfoliation and hydrothermal methods were employed to prepare MoS2 for modification with isolated Co atoms. The results showed that the prepared catalyst had a higher catalytic activity and could be used at lower temperatures. Subsequently, periodic density functional theory (DFT) calculations were used to discuss the effect of isolated Co doping on the catalytic performances of single-layer MoS2. DFT calculations revealed that the electronic structure of the MoS2 basal surface was changed by Co atom doping, making the originally inert basal surface catalytically active. Based on the energetic analysis, the influence of isolated Co atom doping on the adsorption performance, hydrogenolysis activity, and hydrodesulfurization performance of the basal surface is discussed. This work paves a new path for improving HDS catalytic activity via synergistic structure and charge characteristics. [ABSTRACT FROM AUTHOR]

The potential of Al- and Ga-doped graphene (Al–Gr/Ga–Gr) to activate the C–H bond of CH4 by N2O to generate methanol is explored using density functional theory calculations. Both surfaces have a higher affinity for capturing N2O than CH4. The oxidation of CH4 starts with the decomposition of N2O into N2 and Oads species, followed by a hydrogen transfer from CH4 to Oads, resulting in CH3 and HOads species. Our results demonstrate that CH3 combining with HOads to yield CH3OH needs only 0.18 eV on Al–Gr, which is 0.11 eV lower than on Ga–Gr. On the other hand, the competing CO oxidation reaction (CO + Oads → CO2) is inhibited over the Ga–Gr because of its greater activation barrier than the CH4 oxidation process. These findings may provide valuable information for fine-tuning the catalytic activity of graphene-based materials in low-temperature partial oxidation of CH4. [ABSTRACT FROM AUTHOR]

The large amount of carbon dioxide (CO2) emissions has seriously threatened the living environment of human beings. Electrocatalytic conversion of CO2 is one of the most promising methods as it can not only reduce the hazards associated with excessive emissions but also obtain fuels or other chemicals. Current research has found that the changes in the performance of catalysts are caused by the external environment, but their mechanisms affecting CO2 reduction are still not clear enough. Herein, based on density functional theory (DFT) calculations, ions X (X = Cl−, Na+ and S2−) were introduced to change the atomic environment of metalloporphyrins (MPPs). The effects of the atomic environment of the active site on CO2 catalytic performance were systematically investigated. Our results show that the doping of ions regulates the metal electronic state, which can change the CO2 catalytic activity and selectivity on MPPs. Deeply understanding the CO2 reduction mechanism provides a theoretical fundament for designing high-performance and high-selectivity CO2 electrochemical reduction schemes. [ABSTRACT FROM AUTHOR]

Dual-atom catalysts (DACs) have attracted growing research interest recently because of their higher metal atom loading and more flexible active sites compared to single-atom catalysts (SACs). Transitional metal dichalcogenides have been regarded as effective substrates. However, the corresponding research in transition metal dichalcogenides is insufficient for oxygen reactions. In this work, a prototype investigation of dual transition-metal (TM) atoms doped MoTe2 (CoM/MoTe2, M = Fe, Co, Ni, Cu, Zn, Pd, Pt) is performed with density functional theory (DFT). The results indicate that proper dual doping configuration can effectively enhance the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalytic activity of MoTe2 compared to single Co doping. Further research suggests that the regulated electronic property and moderated adsorption strength of reaction intermediates could help to accelerate the OER and ORR processes. This investigation provides an effective strategy for TMD-based catalysts designing by dual transition-metal atoms doping. [ABSTRACT FROM AUTHOR]

Three zirconium–porphyrin based MOFs with different linker connectivity, PCN-222, PCN-223 and PCN-224, and their Zn(II) ion metalated analogues, were prepared and used as catalysts for the photoreduction of CO2 under visible-light irradiation. Before metalation with Zn2+ in the porphyrin linkers, the lowest linker-connected PCN-224 (6-fold) exhibited a higher formate yield rate of 45.2 μmol g−1 h−1 compared to PCN-222 and PCN-223. However, after the incorporation of Zn2+ into the porphyrin, PCN-222-Zn showed the highest formate yield rate of 120.2 μmol g−1 h−1. The density functional theory (DFT) computational results revealed that the catalytic activity correlated with the CO2 adsorption affinity. The CO2 adsorption energy on PCN-222-Zn (294.4 kJ mol−1) was the highest among all of the samples. The overall catalytic performance was affected by the Zr6-oxo cluster connectivity and the introduced dual reaction sites when the porphyrin linkers were metalated with Zn(II) ions. [ABSTRACT FROM AUTHOR]

Colloidal nanoparticles of Earth-abundant, first-row transition metal oxides and sulfide, namely magnetite (Fe3O4), manganese and cobalt ferrite, (MnFe2O4, CoFe2O4), manganese(II) oxide (MnO) and sulfide (α-MnS), were used as catalysts in the cycloaddition between azides and methyl propiolate. The presence of these nanoparticles allowed us to carry out the cycloadditions under milder conditions and with a regioselectivity comparable to the classic "metal-free" thermal processes. Ferrite nanoparticles gave higher conversion than MnO and α-MnS nanoparticles. The feasibility of the cycloaddition onto 1,2-disubstituted acetylenes was also proved. Ferrite nanocatalysts could be magnetically recovered and reused without significant loss of catalytic activity. Density functional theory (DFT) calculations support a mechanistic hypothesis that attributes the increased cycloaddition rate to the adsorption of the azide onto to the nanocatalyst surface. [ABSTRACT FROM AUTHOR]

This work concerns the adsorption and dissociation of CO on doped Ni3M clusters, where M = Sc, Ti, V, Cr, Mn, Fe, Co, Cu, Rh, Ru, Ag, Pd and Pt, applying density functional theory to search for the best catalyst for CO dissociation. Butterfly geometry is observed for Ni3Sc, Ni3Ti and Ni3Cr, while the other clusters retain the distorted tetrahedral geometry. The presence of odd numbers of valence electrons, e.g. in Ni3Sc, Ni3V, Ni3Mn, Ni3Co, Ni3Cu, Ni3Rh and Ni3Ag clusters, allows open shell structures to show greater stability than closed shell clusters. However, the higher stability of the closed shell Ni3Ti cluster is due to the presence of a greater number of polar M–M bonds. Adsorption of CO on all the doped clusters is thermodynamically feasible under standard conditions. Dissociation is not thermodynamically feasible for any of the clusters, except on Ni3Sc. Though doping of any of the metals into the Ni4 cluster decreases the CO dissociation barrier, none of the bimetallic clusters are good catalysts for CO dissociation. The formation of TiO, VO, CoO and MnO species reduces the catalytic activity of the doped Ni4 cluster. Surface C binds at threefold coordination sites for most of the clusters. However, for the Ni3Fe cluster, surface C is tetra-coordinated and strongly binds to Fe, forming a σ and a π bond, and its greater s character favors hydrogenation. Surface O in Ni3Cu binds at threefold sites and has unpaired electrons, making it radical in nature, and more reactive than surface O in the Ni3Fe cluster. Greater positive ΔG values, the lower stability of the doped clusters, and a tendency toward adsorption all reduce the efficiency of the catalyst. Thus, Ni3Fe and Ni3Cu appear to be the best catalysts for CO dissociation. [ABSTRACT FROM AUTHOR]

The focus of this work was on the synthesis, characterization and catalytic activity of Mo(vi) complexes with hemilabile polydentate ligands that show a high tendency to form discrete small-sized self-assembled structures. A series of mononuclear, [MoO2(L1 or 3)(MeOH)] (1a and 3a) and [MoO2(L1)(EtOH)] (1b), and dinuclear, [MoO2(L1–3)]2 (1–3), complexes was synthesised by using 2-aminobenzoylhydrazone ligands derived from salicylaldehyde (H2L1), 3-methoxy-2-hydroxybenzaldehyde (H2L2) and 4-methoxy-2-hydroxybenzaldehyde (H2L3). Different reaction conditions led to the formation of several crystalline forms of the dinuclear cyclic species [MoO2(L1 or 3)]2 (1-α, 1-β, 1-γ, 1·CH3CN, 3-α, 3-β and 3·2CH3CN), a feature which is observed for the first time in the case of the metallosupramolecular compounds incorporating cis-MoO22+ subunits. These complexes were tested as catalysts for cyclooctene epoxidation under eco-friendly reaction conditions by using aqueous tert-butyl hydroperoxide as an oxidant without the addition of an organic solvent. The use of the hemilabile ligands provided the opportunity to employ relatively stable coordinatively saturated dinuclear Mo(vi) complexes, which in turn offered access to highly reactive pentacoordinated species in the presence of olefins. Lastly, the hemilabile ligand induced catalytic enhancement was addressed by using density functional theory calculations. [ABSTRACT FROM AUTHOR]

Herein, CO oxidation on Ni-doped graphene (Ni-Gr) is investigated by first-principle calculations. The strong binding energy (−7.57 eV) of the Ni atom at a single vacancy in graphene and high energy barrier (3.41 eV) for Ni atom mobility in graphene suggest that graphene is stable even after Ni doping, which avoids the problem of metal clustering. The stronger binding interaction between Ni-Gr and O2 than that between Ni-Gr and CO can prevent CO poisoning to Ni-Gr. To explore the catalytic effect of CO oxidation on Ni-Gr, both the Eley–Rideal (ER) and Langmuir–Hinshelwood (LH) mechanisms are investigated. The overall energy barrier at 0 K for the LH and ER mechanisms is 0.63 and 0.77 eV, respectively. At 298.15 K, the overall energy barrier for the LH mechanism decreases to 0.58 eV, whereas that for the ER mechanism increases to 0.88 eV, which implies that CO oxidation on Ni-Gr prefers to proceed via the LH mechanism kinetically. Our results show that the studied system, Ni-Gr, has chemical stability against metal clustering and CO poisoning, and it is a promising catalyst for CO oxidation at mild temperatures. This study provides a good theoretical guideline for the development of Ni-Gr based CO oxidation catalysts. [ABSTRACT FROM AUTHOR]

The range of molybdenum hydride complexes that are sought to participate in the important catalytic hydrodenitrogenation process (HDN) of nitrogen containing polycyclic aromatic hydrocarbons were evaluated by DFT studies. The previously synthesized stable (η6-quinoline)Mo(PMe3)3 complex 1N, in which molybdenum is bonded to the heterocyclic ring, was chosen as a model. The hydrogenation of the quinone heterocycle, which was postulated as the initial step in the overall HDN reaction, is found to occur via three consecutive steps of the oxidative addition of dihydrogen to Mo in 1N. Successive transfer of hydrogen atoms from the metal to the heterocycle leads to the ultimate formation of the tetrahydrido molybdenum intermediate Mo(PMe3)4H413 and 2,2,3,3-tetrahydroquinoline C9H11N 14. All the involved intermediates and transition states have been fully characterized by DFT. This computational modeling of the hydrogenation of quinoline, as a part of extended HDN catalytic processes, provides a fundamental understanding of such mechanisms. [ABSTRACT FROM AUTHOR]

A new chiral linear tetramine (N1-(1-(2-aminophenylamino)propan-2-yl)benzene-1,2-diamine), CLT, and its Schiff base ligand, which was derived from CLT with 2-hydroxybenzaldehyde, was synthesized and transformed into the corresponding manganese(iii) complex. The Schiff base ligand was studied by 1H NMR, 13C NMR, COSY, HSQC, DEPT and microanalysis. Density functional theory (DFT) calculations were performed to determine the structure of the [MnIIIL]+ complex. This manganese complex catalyzes the oxidation of alcohols using 30% H2O2 as an oxidant. Over-oxidation of aldehydes to carboxylic acid and the formation of by-products was not observed. α–β unsaturated alcohol was oxidized smoothly without the oxidation of the double bond. [ABSTRACT FROM AUTHOR]

The ability to improve the intrinsic activity of nanoalloy electrocatalysts is essential for designing highly efficient electrocatalysts by optimizing the basic physical properties of the nanoalloy. This report describes that the electrocatalytic performance of ultrathin PtnCo100-n alloy nanowires (PtnCo100-n NWs) toward the oxygen reduction reaction (ORR) is enhanced by regulating the lattice strain, highly active facets, and the electronic structure of the alloy, which can be achieved by optimizing the ratio of platinum-to-cobalt in alloys. The catalyst of PtnCo100-n nanoalloy NWs features subtle lattice strain and (111) facets. The electrochemical results show excellent activity and durability toward ORR at a Pt:Co ratio of B70: 30, which suggests compressively-strained single-phase alloy state revealed by X-ray diffraction (XRD) results. The correlation of facets, lattice strain, electronic structure, and activity is evaluated by the theoretical model based on the density functional theory (DFT) calculations of nanoalloy clusters, which show electron transfer from the PtCo alloy to oxygen. There is a relatively low energy difference between the HOMO of the PtCo nanoalloy and the LUMO of oxygen as the Pt:Co atom ratio is 70: 30. By analyzing the adsorption of OH, O, and OOH intermediates on the surface of PtCo(111) facets of different compositions, it is observed that the adsorption energy of the Pt2Co8 cluster (Pt: Co20: 80) is the strongest, resulting in low activity. Interestingly, the adsorption energy of the Pt7Co3 cluster is between that of the Pt6Co4 and Pt10 cluster, which is thought to be related to the highest catalytic activity of the nanoalloy when the Pt: Co atom ratio is B70: 30. This finding will provide a new strategy for studying the relationship between the structure and the catalytic activity of nanocatalysts. [ABSTRACT FROM AUTHOR]

Developing highly efficient electrocatalysts for multiple electrode reactions is of great importance for the large-scale applications of some energy conversion and storage devices. In this work, by means of spin-polarized density functional theory (DFT) computations, we have systematically explored the catalytic performance of several palladium (Pdn, n = 1–6, and 13) nanoclusters anchored on the experimentally available defective MoS2 monolayer with S monovacancy (Pdn/MoS2) for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Our results revealed that these studied Pdn/MoS2 materials have high stability due to the strong interaction of Pd clusters with the dangling Mo atoms and the S atoms around the vacancy with the binding energy per Pd atom ranging from −3.12 to −4.36 eV. Interestingly, the ORR/OER catalytic activity of these Pdn/MoS2 catalysts was greatly dependent on the sizes of the anchored Pd clusters: Pd6/MoS2 is predicted to exhibit the highest ORR catalytic activity due to its lowest overpotential of 0.59 V among all the studied catalysts, while Pd2/MoS2 is identified as the best OER catalyst due to its ultra-low overpotential of 0.32 V. Thus, our DFT results suggested that the ORR/OER catalytic performance could be effectively tuned by precisely controlling the sizes of the anchored Pd clusters on the MoS2 monolayer, which provides an important insight to further design novel and efficient ORR/OER catalysts. [ABSTRACT FROM AUTHOR]

Photoreduction of CO2 to hydrocarbons has lately attracted increased attention. Understanding the reaction mechanism of photocatalytic reduction of CO2 is crucial for the development of CO2 photocatalysts. CO2 adsorption and activation are the first steps of CO2 photoreduction. In this work, the adsorption and activation of CO2 on TiO2-supported Au and Au–Cu clusters were studied using density functional theory (DFT) calculations to identify the key factors for improving its adsorption and activation. The presence of Cu atoms was found to have great significance in the adsorption and activation of CO2, and the Cu7 atom on the Au7Cu3/TiO2(101) surface exhibited the strongest CO2 adsorption ability. By analyzing the surface electronic structure, we found that the up-shift of the d-band center toward the Fermi level in the presence of Cu atoms increased the binding strength of CO2. Additionally, the Cu atoms were positively charged on the Au7Cu3/TiO2(101) surface and promoted the adsorption of CO2 by increasing the electrostatic attraction between the O atom of CO2 and the Cu atom. Therefore, compared to the Au10/TiO2(101) surface, the activity of the Au7Cu3/TiO2(101) surface can be definitely improved. Our results can provide useful insights into the design and development of more efficient bimetallic cluster supported TiO2 photocatalysts, which are used as catalysts for the synthesis of hydrocarbon fuels by CO2 hydrogenation. [ABSTRACT FROM AUTHOR]

Converting CO2 into useful fuels and chemicals offers a promising strategy for mitigating the issues of energy crisis and global warming. However, it is still a fundamental challenge to find highly efficient catalysts for the CO2 electrochemical reduction (CO2ER) reaction. In this work, the catalytic performance of heteroatom (B, P, Si, and S)-doped C3N materials as metal-free CO2ER electrocatalysts was investigated by means of density functional theory (DFT) calculations. The results reveal that these heteroatom-doped C3N materials exhibit high stability. On the basis of the calculated Gibbs free energies, BN-doped C3N exhibits superior CO2ER catalytic activity for CO2 reduction to HCOOH with a low overpotential of 0.14 V vs. RHE. The present work demonstrates the promising potential of BN-doped C3N as an active and selective CO2ER catalyst, and provides an effective strategy for electrochemical applications. [ABSTRACT FROM AUTHOR]

Recently, heteroatom co-doped carbon material catalysts have shown extraordinary oxygen reduction reaction (ORR) catalytic activity, but a lack of understanding of the specific mechanism of the ORR has hindered their further development. In this study, we studied the geometric structure, stability, electronic properties, catalytic sites and detailed ORR pathways of P, N co-doped graphene (PN-Gra) by density functional theory (DFT) calculations, trying to reveal the effect of N and P co-doped graphene on the catalytic activity of the ORR. Our calculations indicate that the PN-Gra structure remains stable at high temperature (1000 K) and P, N atoms with their adjacent four carbon atoms constitute the active region to adsorb O2 more efficiently than single phosphorus or nitrogen doped catalysts. Combining energy barrier and free energy diagram analysis, the most favorable pathway is O2* → O* + O* → OH* + O* → 2OH* → OH* + H2O → 2H2O, which is thermodynamically favorable and the associated energy barrier is low, with an overpotential of 0.96 V. After comprehensive analysis and comparison, P, N co-doping does improve the catalytic ability due to the synergistic effect compared to single doping. We believe that this study provides researchers a way to understand the reaction mechanism and ways to improve the catalytic properties of carbon-based materials. [ABSTRACT FROM AUTHOR]