Primary Reduction Product Research Articles

Hydrogen peroxide mediated thermo-catalytic conversion of carbon dioxide to C1-C2 products over Cu (0)

The global challenge concerning CO2 conversion to valuable products is anticipated to execute an essential task towards net zero carbon emissions. Thermal CO2 reduction is advantageous in terms of higher conversion rates, selectivity, and already-established industrial thermal instruments for scalability. However, the method is energy-intensive, a hindrance to sustainably practical adoption. Herein, we present a comprehensive study of H2O2-mediated thermal CO2 conversion in the presence of dendritic zerovalent copper (d-ZCu) in a batch-type reactor, yielding C1 and C2 carbon products, with acetic acid (AcOH) as the major product (achieving an optimized yield of approximately 0.98 M and a selectivity of around 97 % at near ambient conditions of 25–150 °C and 1–15 bar), along with trace amounts of methanol and ethanol, and carbon monoxide (CO) as a gaseous product. The reaction parameters, including temperature, time, pressure, and concentrations, were optimized to gain better insight into the reaction. To further explore the feasibility of the process, experiments were conducted in a continuous flow-packed bed reactor using similar parameters as those in the batch reactor, where CO was identified as the primary product of CO2 reduction. For advanced real-life applicability, the as-emitted exhaust gases from diesel and petrol engines, as sources of anthropogenic CO2, were utilized to establish the practical applicability of the proposed method.

Electron gathering at violet phosphorene-Ag interface for photoreduction of CO2 to ethylene

Selective photoreduction of CO2 into ethylene is desirable but stays challenging due to easy desorption of primary reduction product CO. Herein, violet phosphorene nanosheets (VPNS) are for the first time demonstrated to be effective CO2 photoreduction catalysts to yield ethylene. Photoelectron was found to transfer from VPNS to co-catalyst Ag and aggregated on VPNS-Ag interface to enhance CO2 and CO* adsorption, and further lower the reduction energy barrier to yield ethylene, which was confirmed by in-situ diffuse reflectance infrared Fourier-transform, CO stripping voltammetry, CO reduction experiments, and density functional theory calculations. CO2 is reduced into COOH* and automatically transformed into CO* on VPNS-Ag surface, then protonized into CHO* with a low barrier of 0.64 eV and automatically coupled into COCHO* to yield ethylene. Only ethylene was detected from CO2 photoreduction with a yield of 10.34 μmol g−1 h−1 without any hole-sacrificial agent, much higher than most reported photocatalysts.

Interlayer anions modulated ZnAl-layered double hydroxides for enhanced photocatalytic CO2 reduction

Photocatalytic CO2 reduction has drawn widespread attention across all sectors of society. Layered double hydroxides (LDHs) have emerged as promising photocatalysts, renowned for their adjustable bandgaps and reaction sites. As a typical anionic layered material, LDHs exhibit intricate interactions between interlayer anions and brucite-like metal layers, greatly influencing their inherent physicochemical properties. In this work, we synthesized ZnAl-LDH samples intercalated with four distinct anions: carbonate (CO32–), chloridion (Cl–), nitrate (NO3–), and dodecyl sulfate (DS–), denoted as LDH-CO3, LDH-Cl, LDH-NO3, and LDH-DS, respectively. These LDHs samples have comparable crystallinity and morphology but differ in their interlayer spacing. XRD results reveal interlayer spacings of 0.77 nm for LDH-CO3, 0.78 nm for LDH-Cl, 0.88 nm for LDH-NO3, and 1.24 nm for LDH-DS, between adjacent brucite-like ZnAl hydroxide layers. Remarkably, LDH-NO3 demonstrates the highest photocatalytic CO2 reduction performance, with CO as the primary reduction product. Specifically, the average CO production rate of LDH-NO3 are 3.80 μmol g–1 h–1, surpassing that of LDH-CO3, LDH-Cl, and LDH-DS by 1.9, 2.1, and 2.5 times, respectively. This superior performance can be attributed to the intermediate interlayer spacing of LDH-NO3, which facilitates strong light absorption and a robust local built-in electric field. Theses properties enhance charge generation and separation abilities, leading to efficient photocatalytic reactions. The obtained results highlight the critical role of controlling small molecules within the interlayer, alongside defects, in the design and fabrication of layered-structure photocatalysts. This study provides valuable insights into optimizing the performance of LDH-based photocatalysts for CO2 reduction and potentially other photocatalytic applications.

Electrochemical Reduction of CO2: A Common Acetyl Path to Ethylene, Ethanol or Acetate

Ethylene is well known as the primary product of CO2 reduction at Cu electrocatalysts using zero-gap membrane electrode assembly cells with gas diffusion cathodes. Other types of Cu electrocatalysts including oxide-derived Cu, CuSn and CuSe yield relatively more C2 oxygenates; however, the mechanisms for C2 product selectivity are not well established. This work considers selectivity trends of Cu-P0.065, Cu-Sn0.03, and Cu2Se electrocatalysts made using a standard one pot synthesis method. Results show that Cu-P0.065 electrocatalysts (Cu δ+ = 0.13) retain ethylene as a primary product with relatively higher Faradaic efficiencies (FE = 43% at 350 mA cm−2) than undoped Cu electrocatalysts (FE = 31% at 350 mA cm−2) at the same current density. The primary CO2 reduction product at Cu-Sn0.03 (Cu δ+ = 0.27) electrocatalysts shifts to ethanol (FE = 48% at 350 mA cm−2) while CO2 reduction at Cu2Se (Cu δ+ = 0.47) electrocatalysts favor acetate production (FE = 40% at 350 mA cm−2). Based on these results, we propose a common acetyl intermediate and a mechanism for selective formation of ethylene, ethanol or acetate based on the degree of partial positive charge (δ + ) of Cu reaction sites.

Electrochemical cell design and performance evaluation of polyvinyl ferrocene/carbon nanotube electrodes for selective formate separation

Selective ion separation is a fundamental challenge with applications ranging from the manufacturing of pharmaceuticals & industrial salts to water desalination. In particular, the separation of formate, a primary product of electrochemical carbon dioxide reduction, has attracted attention not only to reduce carbon emissions and energy costs but to provide new routes to value-added chemicals. In the present study, selective formate separation from an aqueous solution is demonstrated using an electrochemical flow cell with symmetric redox-active polyvinyl ferrocene electrodes. An electrosorption system equipped with an electrosorption cell, inline conductivity, and pH sensors was constructed to provide real-time measurements of the formate adsorption performance in continuous flow mode while varying operating conditions such as the flow rate, cell voltage, and electrolyte concentration. These parameters were optimized using a Box–Behnken experimental design to improve the formate adsorption selectivity. The flow cell results showed a selectivity higher than 6.0 toward the removal of formate in an electrolyte containing a 30-fold excess of perchlorate under optimal operation conditions (i.e., 0.5 mL/min flow rate, 1.0 V, and 15 mM electrolyte concentration). The performance of the flow cell was also tested using a solution that contained different liquid CO2 reduction products, and formate separation was achieved. The results suggest that the proper design of the electrochemical cell and efficient operation of the flow platform pave the way for scaling up the technology for selective formate separation.

A novel calculation strategy for optimized prediction of the reduction of electrochemical window at anode

The reduction of the electrochemical window (EW) of electrolytes plays a significant role in assessing their compatibility with the anode in lithium-ion batteries. However, the accurate calculation of the reduction of EW is still challenging due to missing the solvation effects, condensation effects, kinetic factors, and the passivation on anodes. The theoretical prediction of the intrinsic and apparent EW is confirmed by a comprehensive experimental analysis of ethylene carbonate-dimethyl carbonate (EC-DMC) electrolytes, combining linear sweep voltammetry (LSV) and gas chromatography-mass spectrometry (GC-MS). The proposed novel kinetic normal distribution theory model can quantitatively explain the current density from LSV and affirm acetaldehyde (MeCHO) as one of the primary reduction products of EC. The solvent effect restricts the intrinsic EW of EC-DMC without lithium salt to 2.6 V (vs. Li+/Li) arising from the Marcus–Gerischer theory and the passivation of MeCHO on the anode broadens the apparent EW to 0.3 V (vs. Li+/Li) arising from the normal distribution of the lowest unoccupied molecular orbital (LUMO) for MeCHO produced by thermal motion. In addition, the passivation on the anode depends intensively on the lithium salt, resulting in more complicated influences on the apparent EW.

Rare-earth metal-N6 centers in porous carbon for electrocatalytic CO2 reduction.

Single-atom catalysts fabricated using rare earth elements have emerged for electrocatalytic carbon dioxide reduction, but they need to be studied systematically and intensively. Herein, density functional theory was employed to determine the electrocatalytic CO2 reduction activity of rare earth-N6 porous carbon (Re = Ce, Nd, Sm, Eu, Gd, Tb, Er, Tm, Yb, and Lu) single-atom catalysts. The results revealed that the binding energy of the rare-earth atoms to the N6C monolayers in the ten studied Re-N6C monatomic catalysts is much more negative than the cohesion energy of the bulk rare-earth metal, which makes rare-earth atoms stably dispersed in the N6C skeleton. CO is the primary chemical product of electrocatalytic CO2 reduction by Ce, Eu, and Lu. The primary product of the six monatomic species, i.e., Nd, Sm, Tb, Er, Tm, and Yb, is HCOOH. The dominant product of Gd is CH4. The limiting potentials of these catalysts are in the range of 0.31-0.786 V and their overpotentials are in the range of 0.06-0.707 V, all of which are relatively low, showing that they are potential and promising electrocatalysts for CO2 reduction. Subsequently, Eu-N6C was experimentally synthesized and used for electrocatalytic CO2 reduction to obtain CO products, and the overpotential showed good agreement with the theoretically calculated values.

Two-Dimensional (2D) TM-Tetrahydroxyquinone Metal-Organic Framework for Selective CO2 Electrocatalysis: A DFT Investigation.

The resource utilization of CO2 is one of the essential avenues to realize the goal of "double carbon". The metal-organic framework (MOF) has shown promising applications in CO2 catalytic reduction reactions due to its sufficient pore structure, abundant active sites and functionalizability. In this paper, we investigated the electrocatalytic carbon dioxide reduction reactions of single-atom catalysts created by MOF two-dimensional coordination network materials constructed from transition metal-tetrahydroxybenzoquinone using density function theory calculations. The results indicate that for 10 transition metals, TM-THQ single levels ranging from Sc to Zn, the metal atom binding energy to the THQ is large enough to allow the metal atoms to be stably dispersed in the THQ monolayer. The Ni-THQ catalyst does not compete with the HER reaction in an electrocatalytic CO2 reduction. The primary product of reduction for Sc-THQ is HCOOH, but the major product of Co-THQ is HCHO. The main product of Cu-THQ is CO, while the main product of six catalysts, Ti, V, Cr, Mn, Fe, and Zn, is CH4. The limit potential and overpotential of Ti-THQ are the highest, 1.043 V and 1.212 V, respectively. The overpotentials of the other monolayer catalysts ranged from 0.172 to 0.952 V, and they were all relatively low. Therefore, we forecast that the TM-HQ monolayer will show powerful activity in electrocatalytic carbon dioxide reduction, making it a prospective electrocatalyst for carbon dioxide reduction.

Two-Dimensional Transition Metal-Hexaaminobenzene Monolayer Single-Atom Catalyst for Electrocatalytic Carbon Dioxide Reduction.

Electrocatalytic reduction of CO2 to valuable fuels and chemicals can not only alleviate the energy crisis but also improve the atmospheric environment. The key is to develop electrocatalysts that are extremely stable, efficient, selective, and reasonably priced. In this study, spin-polarized density function theory (DFT) calculations were used to comprehensively examine the catalytic efficacy of transition metal-hexaaminobenzene (TM-HAB) monolayers as single-atom catalysts for the electroreduction of CO2. In the modified two-dimensional TM-HAB monolayer, our findings demonstrate that the binding of individual metal atoms to HAB can be strong enough for the atoms to be evenly disseminated and immobilized. In light of the conflicting hydrogen evolution processes, TM-HAB effectively inhibits hydrogen evolution. CH4 dominates the reduction byproducts of Sc, Ti, V, Cr, and Cu. HCOOH makes up the majority of Zn's reduction products. Co's primary reduction products are CH3OH and CH4, whereas Mn and Fe's primary reduction products are HCHO, CH3OH, and CH4. Among these, the Ti-HAB reduction products have a 1.14 eV limiting potential and a 1.31 V overpotential. The other monolayers have relatively low overpotentials between 0.01 V and 0.7 V; therefore, we predict that TM-HAB monolayers will exhibit strong catalytic activity in the electrocatalytic reduction of CO2, making them promising electrocatalysts for CO2 reduction.

Enhanced coagulation and oxidation by the Mn(VII)-Fe(III)/peroxymonosulfate process: Performance and mechanisms

To improve the performance of the conventional coagulation process, a permanganate (Mn(VII)) pre-oxidation combined with Fe(III)/peroxymonosulfate (PMS) coagulation process (Mn(VII)-Fe(III)/PMS) that can significantly improve the removal of dissolved organic carbon (DOC), turbidity, and micropollutants is proposed in this study. Compared with conventional Fe(III) coagulation, the Mn(VII)-Fe(III)/PMS process can also significantly enhance the removal of iohexol and sulfamethoxazole in raw water. During this process, the primary reduction product, Mn(IV), after Mn(VII) pre-oxidation was adsorbed on the floc surfaces and involved in the Fe(III)/PMS process. The natural organic matter (NOM) in raw water mediated the redox cycle of iron. The synergistic effect of NOM, Fe, and Mn facilitated the redox cycle of Mn(III)/Mn(IV) and Fe(III)/Fe(II) to promote the activation of PMS. The sulfate radical (SO4•−) played an important role in the degradation of micropollutants. The formation potential of the detected volatile disinfection by-product (DBP) during the subsequent chlorination was reduced by 21.9% after the Mn(VII)-Fe(III)/PMS process. This study demonstrated the promising application of the Mn(VII)-Fe(III)/PMS process for coagulation and micropollutant control and illustrated the reaction mechanism. This study provides guidance for improving conventional drinking water treatment processes.

Cooperative pathway of O2 reduction to H2O2 in chloroplast thylakoid membrane: new insight into the Mehler reaction.

Oxygen reduction in chloroplasts in the light was discovered by (Mehler Arch Biochem Biophys 33:65-77, 1951) as production of hydrogen peroxide. Later, it was shown that the primary product of the oxygen reduction is superoxide radical produced in thylakoids by one-electron transfer from reduced components of photosynthetic electron transport chain to O2 molecule. For a long time, the formation of hydrogen peroxide was considered to be a result of disproportionation of superoxide radicals in chloroplast stroma. Here, we overview a growing number of evidence indicating on another one, additional to disproportionation, pathway of hydrogen peroxide formation in chloroplasts, namely its formation in thylakoid membrane due to reaction of superoxide radical generated in the membrane with the reduced plastoquinone molecule, plastohydroquinone. Since various components of photosynthetic electron transport chain (primarily photosystem I) can supply superoxide radicals to this reaction, we refer this two-step O2 photoreduction to H2O2 as a cooperative process. The significance of hydrogen peroxide production via this pathway for redox signaling and scavenging of reactive oxygen species is discussed.

Understanding the Effect of Lithium Nitrate As Additive in Carbonate Based Electrolytes for Silicon Anodes

Owed to its high specific capacity and its natural abundance, silicon is one of the most promising anode materials for next generation lithium-ion batteries. However, large volumetric changes of silicon upon (de-)lithiation of ~300 % lead to severe degradation phenomena such as particle pulverization and rupture of the solid electrolyte interphase (SEI), resulting in continuous electrolyte consumption and irreversible loss of lithium upon cycling.[1-3] Electrolyte additives such as FEC can improve the cycling performance of silicon anodes significantly by forming a more stable and effective SEI, which can accommodate the morphological changes. However, FEC has only a limited thermal stability when used with LiPF6 as electrolyte salt[4] and shows higher gassing compared to an EC-based electrolyte.[5] Lithium nitrate (LiNO3), predominantly used to passivate the lithium metal electrode in Li-sulfur or Li-air battery systems, was recently demonstrated to be also an efficient additive for silicon anodes.[6-9] In contrast to FEC, the reaction mechanism of LiNO3 in carbonate-based electrolyte systems is not completely understood yet.In the present study, the reduction mechanism of LiNO3 and LiNO2 in 1 M LiPF6 in EC/DEC (1:2, v:v) is investigated using cyclic voltammetry on carbon black electrodes with a high surface area (C65/PvDF 5:5 w/w; 4.8 m2 BET cm-2 el) in half-cells, further supported by post mortem investigations on the harvested electrodes via X-ray photoelectron spectroscopy (XPS). First, the reductive features of LiNO3 and LiNO2 are identified: here, two distinct features with peaks at 1.56 V vs. Li+/Li and 1.39 V vs. Li+/Li are observed for the LiNO3-based electrolyte (see Figure 1). However, the electrolyte containing LiNO2 revealed only the second feature at 1.39 V vs. Li+/Li, indicating that this peak is the reduction feature of LiNO2 as compared to the feature at 1.56 V vs. Li+/Li corresponding to the reduction of LiNO3 to LiNO2. In addition, no EC reduction feature is perceived at 0.8 V vs. Li+/Li for both additives, suggesting the complete and effective passivation of the C65 particle surface by LiNO3 and LiNO2 before the EC reduction potential is reached. Combining these findings with the post mortem XPS analysis we deduced the reduction reaction mechanism of LiNO3. We found that the primary reduction product of LiNO3 – also reported in literature to be LiNO2 [10,11] – is soluble in carbonate-based electrolyte systems and therefore does not act as direct SEI component. Both, LiNO3 and LiNO2 are finally tested as electrolyte additives in long term cycling experiments in Si||NMC622 full-cells, comparing the performance with the additive-free electrolyte.

Pendent Relay Enhances H2O2 Selectivity during Dioxygen Reduction Mediated by Bipyridine-Based Co-N2O2 Complexes.

Generally, cobalt-N2O2 complexes show selectivity for hydrogen peroxide during electrochemical dioxygen (O2) reduction. We recently reported a Co(III)-N2O2 complex with a 2,2'-bipyridine-based ligand backbone which showed alternative selectivity: H2O was observed as the primary reduction product from O2 (71 ± 5%) with decamethylferrocene as a chemical reductant and acetic acid as a proton donor in methanol solution. We hypothesized that the key selectivity difference in this case arises in part from increased favorability of protonation at the distal O position of the key intermediate Co(III)-hydroperoxide species. To interrogate this hypothesis, we have prepared a new Co(III) compound that contains pendent -OMe groups poised to direct protonation toward the proximal O atom of this hydroperoxo intermediate. Mechanistic studies in acetonitrile (MeCN) solution reveal two regimes are possible in the catalytic response, dependent on added acid strength and the presence of the pendent proton donor relay. In the presence of stronger acids, the activity of the complex containing pendent relays becomes O2 dependent, implying a shift to Co(III)-superoxide protonation as the rate-determining step. Interestingly, the inclusion of the relay results in primarily H2O2 production in MeCN, despite minimal difference between the standard reduction potentials of the three complexes tested. EPR spectroscopic studies indicate the formation of Co(III)-superoxide species in the presence of exogenous base, with greater O2 reactivity observed in the presence of the pendent -OMe groups.

Polymer Chromophore–Catalyst Assembly for Photocatalytic CO2 Reduction

A polystyrene-based chromophore–catalyst assembly (PS-RuC/RuCat) was synthesized and applied for photocatalytic CO2 reduction in an organic solution in the presence of a sacrificial donor. The polymer assembly contains Ru(bpy)32+ (RuC, bpy = 2,2′-bipyridine) as the chromophore and a derivative of [Ru(tpy)(6-mbpy)(CH3CN)]2+ (RuCat, tpy = 4′-phenyl-2,2′:6′,2″-terpyridine and 6-mbpy = 6-methyl-2,2′-dipyridyl) as the CO2 reduction catalyst. The photophysical and electrochemical properties of the polymer assembly were investigated. Picosecond transient absorption and time-resolved emission reveal that the RuC chromophores are quenched by energy transfer to the RuCat units in the polymer assembly. Cyclic voltammetry shows that PS-RuC/RuCat effects electrocatalytic reduction of CO2 with an onset of approximately −1.25 V versus Ag/AgCl. Photocatalytic studies were conducted separately for the PS-RuC/RuCat polymer assembly and a mixture of monomers RuC and RuCat in a mixture of dimethylformamide and triethanolamine with 1-benzyl-1,4-dihydronicotinamide as a sacrificial reductant. The primary CO2 reduction products CO and H2 were detected in both photocatalytic systems. Formic acid was detected at low levels by nuclear magnetic resonance and is a very minor product. The polymer assembly system shows a lower photocatalytic CO2 reduction quantum yield (6.7%) but exhibits improved stability compared with a mixed molecular chromophore/catalyst system.

PdAg Alloy Nanocatalysts: Toward Economically Viable Nitrite Reduction in Drinking Water

Nitrite (NO2–) is the primary reduction product of nitrate (NO3–), which is the most predominant contaminant in global freshwater. Both species present major environmental challenges; NO2– is also ...

Guanine-adenine interactions in DNA tetranucleotide cation radicals revealed by UV/vis photodissociation action spectroscopy and theory.

Hydrogen-rich cation radicals (GATT + 2H)+˙ and (AGTT + 2H)+˙ represent oligonucleotide models of charged hydrogen atom adducts to DNA. These tetranucleotide cation radicals were generated in the gas phase by one-electron reduction of the respective (GATT + 2H)2+ and (AGTT + 2H)2+ dications in which the charging protons were placed on the guanine and adenine nucleobases. We used wavelength-dependent UV/Vis photodissociation in the valence-electron excitation region of 210-700 nm to produce action spectra of (GATT + 2H)+˙ and (AGTT + 2H)+˙ that showed radical-associated absorption bands in the near-UV (330 nm) and visible (400-440 nm) regions. Born-Oppenheimer molecular dynamics and density-functional theory calculations were used to obtain and rank by energy multiple (GATT + 2H) dication and cation-radical structures. Time-dependent density functional theory (TD-DFT) calculations of excited-state energies and electronic transitions in (GATT + 2H)+˙ were augmented by vibronic spectra calculations at 310 K for selected low-energy cation radicals to provide a match with the action spectrum. The stable product of one-electron reduction was identified as having a 7,8-dihydroguanine cation radical moiety, formed by intramolecular hydrogen atom migration from adenine N-1-H. The hydrogen migration was calculated to have a transition state with a low activation energy, Ea = 96.5 kJ mol-1, and positive activation entropy, ΔS‡ = 75 J mol-1 K-1. This allowed for a fast isomerization of the primary reduction products on the ion-trap time scale of 150 ms that was substantially accelerated by highly exothermic electron transfer.

A Technological and Typological Analysis of Lithic Material from Skovmosen I, Denmark

During road construction work, material attributed to the Final Palaeolithic was discovered at Skovmosen I, near Kongens Lyngby on Zealand, eastern Denmark. Although it is regularly mentioned in reviews of the southern Scandinavian Final Palaeolithic, the Skovmosen I assemblage has hitherto remained poorly described. We here review the site’s discovery history and its context. Aided by a three-dimensional digital recording protocol, this article details the assemblage composition and its technology. The assemblage is comprised of tanged points, scrapers and burins, alongside blades and cores as primary reduction products. Although evidently disturbed by the road construction that led to the site’s discovery, the material likely reflects the remains of a small Final Palaeolithic locale, where diverse activities were carried out.

Reaction-based kinetic model for the reduction of supported NiO oxygen transfer materials by CH4

Abstract The focus of this study is to assess the reaction rate-based kinetics of three NiO-based oxygen transfer materials (OTMs) supported on ZrO2, Al2O3 and SiO2 under CH4 reduction. Both NiO weight change data and gaseous phase composition from TGA-MS tests are utilized for the elucidation of the reaction scheme. We show that mainly CH4, as well as CO and H2 (primary NiO reduction products by CH4), are involved in the reduction process under a varying extent that depends on the support used. The developed kinetic model is first order dependent on the concentration of the main reductant at each reaction and a function of the NiO/Ni concentration. On ZrO2, NiO is exclusively reduced by CH4 via both total and partial oxidation. On the other hand, in addition to CH4, CO and H2 also contribute to NiO reduction on Al2O3 and SiO2. Still, total and partial CH4 oxidation are the dominant routes. In the case of SiO2 in particular, the reduction rate of NiO by CO and H2 is the highest among all OTMs. The CH4 decomposition reaction, catalyzed by the metallic nickel sites, also takes place via the Langmuir-Hinshelwood mechanism after the completion of the NiO reduction. The rate of this reaction correlates with the surface area of the materials due to the higher population of active metallic nickel sites on the surface, leading to carbon deposition in the order NiO/Al2O3 > NiO/SiO2 > NiO/ZrO2.

Efficient electrocatalytic reduction of carbon dioxide by metal-doped β12-borophene monolayers.

Electrochemical reduction of CO2 to value-added chemicals and fuels shows great promise in contributing to reducing the energy crisis and environment problems. This progress has been slowed by a lack of stable, efficient and selective catalysts. In this paper, density functional theory (DFT) was used to study the catalytic performance of the first transition metal series anchored TM–Bβ12 monolayers as catalysts for electrochemical reduction of CO2. The results show that the TM–Bβ12 monolayer structure has excellent catalytic stability and electrocatalytic selectivity. The primary reduction product of Sc–Bβ12 is CO and the overpotential is 0.45 V. The primary reduction product of the remaining metals (Ti–Zn) is CH4, where Fe–Bβ12 has the minimum overpotential of 0.45 V. Therefore, these new catalytic materials are exciting. Furthermore, the underlying reaction mechanisms of CO2 reduction via the TM–Bβ12 monolayers have been revealed. This work will shed insights on both experimental and theoretical studies of electroreduction of CO2.

Deoxidation Mechanism in Reduced Titanium Powder Prepared by Multistage Deep Reduction of TiO2

There are technical bottlenecks in the preparation of metallic titanium powder by conventional thermal reduction of TiO2 with calcium, magnesium, or other metals, such as low efficiency and incomplete deoxidation. Based on the thermodynamic equilibrium characteristics of the step-by-step reduction of TiO2, a comparative study method was used, and the thermodynamic and kinetic differences between thermal reduction reactions of TiO2 with magnesia and calcium were investigated in this paper. Considering the difference in the electronegativity characteristics between magnesium and calcium, a new idea was put forward that the primary reduction product is prepared through a primary reduction process of TiO2 in the form of magnesiothermic self-propagating high-temperature synthesis (SHS), and then the reduced titanium powder is obtained through the primary reduction product for a deep calcium-thermal reduction reaction. The reduction degree and mechanism of TiO2 during the primary magnesium thermal reaction and deoxidation mechanism of primary reduction products in different deep reduction modes were investigated in this paper. The results showed that it is more conducive to undergo complete deoxygenation such that the primary reduction product is first acid impregnated, followed by deep calciothermic reduction. High-purity reduced titanium powder with a final oxygen content of only 0.21 pct and purity greater than 99.0 pct was obtained.