Catalytic Poisoning Research Articles

Influence of Catalyst Surface Structure on the Electrochemical Hydrogenation of Cis,Cis-Muconic Acid

Adipic acid (AA) production from petroleum-based cyclohexane is one of the largest chemical processes in terms of annual volumetric turnover accounting for 3 million tons as of 2022. The current commercial approach to synthesize AA is through the oxidation of petroleum-derived cyclohexane using nitric acid. The release of N2O in stoichiometric amounts makes it one of the most significant greenhouse gas (GhG) emitting processes. The abundance of biomass in the Midwestern United States has driven significant research efforts to synthesize bio-derived and sustainable commodity products and lower the chemical industry’s carbon footprint.1 cis,cis-Muconic acid (ccMA), a biobased C6 diunsaturated diacid platform molecule can be transformed to commodity chemicals like caprolactam, adipic acid, and terephthalic acid, with AA being of particular interest for the synthesis of nylon 6,6.2 For the first time in literature, we demonstrate appreciable production of AA (conversion: 91%, selectivity: >95%) through electrochemical hydrogenation (ECH) of ccMA on PGM catalysts. Carbon-supported palladium (Pd/C) and platinum (Pt/C) selectively produced AA while bulk Pd and Pt yielded the monounsaturated trans-3-hexenedioic acid (t3HDA) intermediate and H2 under all tested conditions. Such an influence of surface structure on the electrochemistry of organics is not unprecedented. Koper et. al3 studied Pt single crystals for the electrochemical hydrogenation of acetone and showed how activity, selectivity, and extent of catalytic poisoning are highly sensitive to the Pt surface structure. Similarly, we used density functional calculations to elucidate the structure-sensitive nature of ccMA ECH and its intermediates by identifying thermodynamically preferred reaction pathways as a function of surface geometry (terrace vs steps). The energetics coupled with experimental observations suggest that the reduction of ccMA to t3HDA occurs through an outer sphere proton-coupled electron transfer mechanism, while the reduction of HDA to AA preferentially occurs on Pd and Pt (111), the most abundant facet in Pd/C and Pt/C. Our calculations also explain the exceptional performance of Pd/C compared to Pt/C by the weaker binding of Pd terrace sites compared to Pt. Overall, combining renewable electricity, in-situ hydrogen generation from water, and a biologically-produced intermediate enabled us to open a sustainable route for bio-adipic acid production. This allows us to further design and optimize the catalyst for the selective production of biobased AA.

Optimizing potassium polysulfides for high performance potassium-sulfur batteries.

Potassium-sulfur batteries attract tremendous attention as high-energy and low-cost energy storage system, but achieving high utilization and long-term cycling of sulfur remains challenging. Here we show a strategy of optimizing potassium polysulfides for building high-performance potassium-sulfur batteries. We design the composite of tungsten single atom and tungsten carbide possessing potassium polysulfide migration/conversion bi-functionality by theoretical screening. We create two ligand environments for tungsten in the metal-organic framework, which respectively transmute into tungsten single atom and tungsten carbide nanocrystals during pyrolysis. Tungsten carbide provide catalytic sites for potassium polysulfides conversion, while tungsten single atoms facilitate sulfides migration thereby significantly alleviating the insulating sulfides accumulation and the associated catalytic poisoning. Resultantly, highly efficient potassium-sulfur electrochemistry is achieved under high-rate and long-cycling conditions. The batteries deliver 89.8% sulfur utilization (1504 mAh g-1), superior rate capability (1059 mAh g-1 at 1675 mA g-1) and long lifespan of 200 cycles at 25 °C. These advances enlighten direction for future KSBs development.

The Tishchenko reaction mediated by organo-f-complexes: the myths and obstacles.

For over a century, the Tishchenko reaction has been a valuable technique for synthesizing esters from aldehydes, serving a variety of applications in different domains. Beyond the remarkable advances in organoactinide and organolanthanide chemistry over the past two decades, there has been a significant increase in the research of the electrophilic d0/fn chemistry of organoactinide and organolanthanide compounds due to the captivating interplay between their structure and reactivity, and their exceptional performance in various homogeneous catalytic processes. The remarkable influence of ligand design, both in terms of steric hindrance and electronic properties, on the catalytic activity of organo-f-element complexes in organic transformations is well-established. However, the traditional view was that the significant oxophilicity of actinide and lanthanide complexes makes them unfavorable for reactions involving oxygen because of catalytic poisoning and their applications have been relatively limited, primarily focused on hydroalkoxylation, small-molecule activation, and cyclic ester polymerization. This review dissects the intricate interplay between ligand design and catalytic activity in actinide and lanthanide complexes, specifically in the context of the Tishchenko esterification.

Metal–organic framework derived synergistic carbon nanoarchitectures boost bifunctional electrocatalytic performances toward methanol oxidation and oxygen reduction in Pt-nanoparticles

Anchoring platinum (Pt) catalysts on appropriate supports through nanoarchitectonics is crucial in achieving a desirable high-performance electrode with low Pt content for direct methanol fuel cells (DMFCs). This manuscript presents the development of two low Pt-content electrocatalysts, Pt-NP@CNR and Pt-NP@CNF, synthesized from the same precursor MOF via two different pyrolysis techniques. Comparative experimental results demonstrate that the Pt-NP@CNR exhibits superior bifunctional activity for the Methanol Oxidation Reaction (MOR) and Oxygen Reduction Reaction (ORR) compared to Pt-NP@CNF. This enhanced performance is attributed to the synergistic effect between Pt-NPs and the high-surface area of porous carbon rod, which serves as the base material in Pt-NP@CNR. Pt-NP@CNR displays an impressive mass activity of 2.12 A mgPt−1, with exceptional cycle stability and minimal catalytic poisoning during MOR. Additionally, it achieves a remarkable E1/2 value of 0.71 V (vs. RHE), a maximum kinetic current density of approximately 2.13 mA cm−2, and low peroxide production, outperforming Pt-NP@CNF and commercial 10 % Pt/C in an alkaline medium. These findings demonstrate Pt-NP@CNR as a promising candidate for future commercializing of an efficient electrode for DMFCs due to its outstanding catalytic performance and versatile characteristics.

Effect of the Fe2O3@TiO2 core-shell structure on CO catalytic oxidation and SO2 poisoning resistance

The core-shell Fe2O3@TiO2 and FeTiOx mixed oxide catalysts were prepared to explore the effect of the core-shell structure on the catalytic oxidation of CO under a high concentration of SO2. The core-shell structure helped inhibit the sintering of nanoparticles and enabled Fe2O3@TiO2 to share a larger specific surface area, pore size and more active chemisorbed oxygen species than FeTiOx, promoting the CO catalytic performance. FeTiOx and Fe2O3@TiO2 reached 84% and 96% conversion efficiency in the flue gas containing 1000 ppm CO at 300 °C. When SO2 was added to the flue gas, the CO conversion efficiency of FeTiOx dropped to about 10% after 5 h, while Fe2O3@TiO2 still achieved 60% CO conversion efficiency. The TiO2 shell of Fe2O3@TiO2 reacted with SO2 to protect the inner active sites from exposure to SO2, while the FeTiOx surface without shell protection was deposited by ferric sulfate and deactivated. Although the amount of sulfate on Fe2O3@TiO2 was larger than that on FeTiOx, the poor thermal stability of titanic sulfate made it decompose more easily than ferric sulfate. Therefore, the core-shell structure showed a critical role in promoting the resistance to SO2-poisoning of Fe2O3@TiO2 in CO catalytic oxidation.

Catalytic Deactivation and Regeneration of Nickel Microparticle in a Home-build Microchannel-coupled-Millireactor: Substrate-Specificity and Multiphase Flow Dependency.

Substrate-assisted product desorption often proposed in heterogeneous catalysis (nanozymes) denounces the catalytic deactivation of heterogenous catalysts. On contrary, the catalytic deactivation of rigid heterogeneous catalysts becomes noticeable in a continuous flow reactor. Surprisingly, it has been addressed inadequately and in an isolated manner. In this study, we have developed a cost-effective non-lithographic method for fabrication of PDMS-based microchannel-coupled-millireactor. Immobilized Nickel particles are resistant to leaching in flow process. During continuous operation, millireactors show strong catalytic activity for reduction of resazurin andp-nitrophenol with a conversion rate of almost 100%. The catalytic poisoning is ubiquitous and being gradually prominent whereas complete catalytic deactivation of magnetic Ni-microparticle is found to be an instantaneous process. Relatively larger-sized resorufin binds predominantly to the surface and thereby blocks the access of substrate to Ni-particle. The dissociations of product molecules - resorufin and p-aminophenol are the rate-limiting steps that caused the abrupt deactivation of Ni-microparticle. The kinetic mechanism of heterogeneous derived from the Langmuir-Hinshelwood mechanism satisfactorily explain the catalytic poisoning and deactivation of Nickel microparticle. This study sheds light on the intricacies of catalytic activity and poisoning of magnetic Nickel microparticles.

Does the Spin State and Oriented External Electric Field Boost the Efficiency of Fe(II) Pincer Catalyst toward CO2Hydrogenation Reaction?

In this study, we have explored the catalytic reactivities of four PNP-pincer supported Fe(II) complexes, namely, [(iPrPNMeP)FeH2(CO)] (1), [(iPrPNMeP)FeH(CO)(BH4)] (2), [(iPrPNHP)FeH2(CO)] (3), and [(iPrPNMeP)FeH(BH4)] (4) (iPrPNMeP = MeN{CH2CH2(PiPr2)}2 and iPrPNHP = HN{CH2CH2(PiPr2)}2) toward reductive CO2 hydrogenation for formate production. Our density functional theory and ab initio complete active space self-consistent field study have identified three fundamental steps in this catalytic transformation: (i) anchoring of the CO2 molecule in the vicinity of the metal using noncovalent interactions, (ii) catalyst regeneration via H2 cleavage, and (iii) formate rebound step leading to catalytic poisoning. The variations in the catalytic efficiency observed among these catalysts were attributed to either easing of steps (i) and (ii) or the hampering step (iii). This can be achieved in various chemical/non-chemical ways, for instance, (a) incorporation of strong-field ligands such as CO facilitating single-state reactivity and eliminating two-state reactivity that generally enhances the rate and (b) inclusion of Lewis acids such as LiOTf and strong bases found to either avoid catalytic poisoning or ease the H-H cleavages, to enhance the rate of reaction (c) evading mixing of excited open-shell singlet states to the ground closed-shell singlet state that hampers the catalytic regeneration. We have probed the role of oriented external electric fields (OEEFs) in the entire mechanistic profile for the best and worst catalyst, and our study suggests that imposing OEEFs opposite to the reaction axis (z-axis) fastens the catalytic regeneration step and, at the same time, hampers catalytic poisoning. The application of OEEFs is found to regulate the energetics of various spin states and can hamper two-state reactivity, therefore increasing the efficiency. Thus, this study provides insights into the CO2 hydrogenation mechanism where the role of bases/Lewis acid, ligand design, spin states, and electric field in a particular direction has been established and is, therefore, likely to pave the way forward for a new generation of catalysts.

Synthesis and characterization of NiCr2O3-CeO2NRs anode electrocatalyst for ethanol electrooxidation reaction in alkaline media.

In this paper, ceria (CeO2) nanorod (NR) supported Ni-Cr2O3 anode electrocatalysts were synthesized as nonnoble metal-based anode electrocatalysts for ethanol electrooxidation reaction (EOR) in alkaline media. Physicochemical characterization of the electrocatalysts was investigated by XRD, SEM, and TEM techniques. Electrochemical performances of the catalysts were investigated via cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronoamperometry (CA) techniques. The data from linear LSV were used for the diffusion coefficient of the electrocatalysts. The CA experiments' results showed the tolerance for catalytic poisoning and durability of the synthesized electrocatalysts.

Unraveling Molecular Fingerprints of Catalytic Sulfur Poisoning at the Nanometer Scale with Near-Field Infrared Spectroscopy.

Fundamental understanding of catalytic deactivation phenomena such as sulfur poisoning occurring on metal/metal-oxide interfaces is essential for the development of high-performance heterogeneous catalysts with extended lifetimes. Unambiguous identification of catalytic poisoning species requires experimental methods simultaneously delivering accurate information regarding adsorption sites and adsorption geometries of adsorbates with nanometer-scale spatial resolution, as well as their detailed chemical structure and surface functional groups. However, to date, it has not been possible to study catalytic sulfur poisoning of metal/metal-oxide interfaces at the nanometer scale without sacrificing chemical definition. Here, we demonstrate that near-field nano-infrared spectroscopy can effectively identify the chemical nature, adsorption sites, and adsorption geometries of sulfur-based catalytic poisons on a Pd(nanodisk)/Al2O3 (thin-film) planar model catalyst surface at the nanometer scale. The current results reveal striking variations in the nature of sulfate species from one nanoparticle to another, vast alterations of sulfur poisoning on a single Pd nanoparticle as well as at the assortment of sulfate species at the active metal–metal-oxide support interfacial sites. These findings provide critical molecular-level insights crucial for the development of long-lifetime precious metal catalysts resistant toward deactivation by sulfur.

Identification of Catalytic Active Sites for Durable Proton Exchange Membrane Fuel Cell: Catalytic Degradation and Poisoning Perspectives.

Recent progress in synthetic strategies, analysis techniques, and computational modeling assist researchers to develop more active catalysts including metallic clusters to single-atom active sites (SACs). Metal coordinated N-doped carbons (M-N-C) are the most auspicious, with a large number of atomic sites, markedly performing for a series of electrochemical reactions. This perspective sums up the latest innovative and computational comprehension, while giving credit to earlier/pioneering work in carbonaceous assembly materials towards robust electrocatalytic activity for proton exchange membrane fuel cells via inclusive performance assessment of the oxygen reduction reaction (ORR). M-Nx -Cy are exclusively defined active sites for ORR, so there is a unique possibility to intellectually design the relatively new catalysts with much improved activity, selectivity, and durability. Moreover, some SACs structures provide better performance in fuel cells testing with long-term durability. The efforts to understand the connection in SACs based M-Nx -Cy moieties and how these relate to catalytic ORR performance are also conveyed. Owing to comprehensive practical application in the field, this study has covered very encouraging aspects to the current durability status of M-N-C based catalysts for fuel cells followed by degradation mechanisms such as macro-, microdegradation, catalytic poisoning, and future challenges.

Halometallate ionic liquids: thermal properties, decomposition pathways, and life cycle considerations

A balance between cost, impact, and physicochemical properties is crucial for halometallate ILs, especially considering their susceptibility to catalytic poisoning.

Pyrrolic, pyridinic, and graphitic sumanene as metal‐free catalyst for oxygen reduction reaction – A density functional theory study

AbstractThis study investigates the nitrogen (N)‐doped sumanene (SUMA) molecule's catalytic behavior for the four‐electron oxygen reduction reaction (ORR) process. Accordingly, the N atom is doped at three different positions on the SUMA molecule to obtain the pyrrolic, pyridinic, and graphitic SUMA. The free energy value for the individual reaction processes in the four‐electron reduction reaction shows high exothermicity and feasibility for the N‐doped SUMA molecules. Moreover, the free energy for the entire four‐electron reduction reaction lies well below the value of O2 reduction into two water (H2O) molecules –474.71 kJ/mol. The N‐doped SUMA molecules exhibit stronger adsorption energy despite being metal‐free. The physisorption of the final product (H2O molecule) over the SUMA molecules suggests the possibility of regeneration of the catalyst, thereby controlling catalytic poisoning. Specifically, the graphitic SUMA shows a prominent catalytic behavior due to a lower highest occupied molecular orbital‐lowest unoccupied molecular orbital energy gap, which arises due to the increased charge density of the carbon atoms present near the graphitic N site. Besides, doping carbon‐based materials with N at the central benzene ring significantly enhances their catalytic efficiency due to localized π‐orbitals. Overall, the results reveal that N‐doped SUMA molecules are a promising metal‐free catalyst for ORR activity.

Low concentration hydrogen peroxide decomposition inside a minichannel with annual silver catalyst

Hydrogen peroxide is a green propellant which apart from space propulsion is used in various industrial applications. Though hydrazine was used initially, the nature of hydrazine which is a toxic, carcinogenic and hazardous fuel resulted in various space agencies’ interest in green propellants. The essential step for high test peroxide (HTP) as a green mono propellant realization is on development of a reliable, effective, long life catalytic beds which are not affected by catalytic poisoning and impurities. In the present study, a 3D model is developed using COMSOL Multiphysics software to know the catalytic decomposition of 30% hydrogen peroxide flowing inside a 3 mm diameter 300 mm length channel. The effect of annular silver catalyst (I.D – 1.6 mm, O.D. – 2 mm, length 10 mm) on decomposition rate is studied in detail. The positioning of silver catalyst bed and number of beds increased the reaction rate with varying pressure drop. Among the variations simulated, the 4 catalyst model gives the better performance and gets decomposed to a greater extent. This model will help in the design of a micro thruster which can operate efficiently with low pressure drop.

Platinum nanoparticles/phosphotungstic acid nanorods anchored poly(diphenylamine) nanohybrid coated electrode as a superior electro-catalyst for oxidation of methanol

Solvation of energy crises is the need of the era which urges for alternate energy resources. Direct methanol fuel cells (DMFCs) are an integral part of alternate energy and fuel concerns. This study demonstrates the facile fabrication of polydiphenylamine/phosphotungstic acid/platinum (PDPA/PTA/Pt) nanocomposites modified electrode via electrodeposition method for efficient electro-oxidation of methanol in acidic medium. The physicochemical characterization of PDPA/PTA/Pt nanocomposite modified electrode morphology using SEM with EDX mapping, and crystallinity behavior was examined using powder XRD analysis. The morphology of the PDPA/PTA/Pt nanocomposites demonstrates that the size of Pt nanospheres is ~200 nm, and the size of PTA nanorods is ~300 nm in the PDPA matrix. The electrochemical properties were also evaluated using cyclic voltammetry, chronoamperometric and electrochemical impedance studies techniques. The PDPA/PTA/Pt nanocomposite modified electrode showed superior electrocatalytic activity, higher current density (14.807 mA cm−2), longer stability and durability (30 min), and excellent catalytic poisoning tolerance to carbonaceous species accumulation towards methanol electro-oxidation reaction (MEOR), which is because of the synergistic existence of Pt nanospheres and PTA nanorods with PDPA matrix which enhances the electron transfer. The obtained results proved that the developed electro-catalyst is an excellent alternative for efficient MEOR in fuel cells applications.

Engineering ionomer homogeneously distributed onto the fuel cell electrode with superbly retrieved activity towards oxygen reduction reaction

Polymer electrolyte fuel cell electrode, especially at lower Pt loadings, suffer from an inevitable performance reduction, primarily as a result of reduced catalytic activity and enlarged mass-transport resistance triggered by ionomer layer enveloping Pt. In course of the conventional slurry method, severe agglomeration leads to formation of larger ionomer particles attributed to electrostatic attraction between sulfonic acid groups and Pt, effectuating catalytic poisoning and creating substantially tortuous pathways for O2. Here, we propose an electrode architecture with infinitesimally thin ionomer deposited onto Pt using electrostatic spray deposition under hot and humid environments. The resultant electrode possesses a hierarchical structure with distinctively homogeneous distribution of ionomer, enabling tripled mass activity and doubled cell performance when compared to the state-of-the-art decal-transferred electrode, and concurrently, improved stability towards carbon degradation. Given the cost-effectiveness and excellent scalability, this work leads the way towards a sustainable trajectory in the long-term targets on global hydrogen mobility.

Pr-Doping Motivating the Phase Transformation of the BaFeO3-δ Perovskite as a High-Performance Solid Oxide Fuel Cell Cathode.

Intermediate temperature solid oxide fuel cells (IT-SOFCs) have been extensively studied due to high efficiency, cleanliness, and fuel flexibility. To develop highly active and stable IT-SOFCs for the practical application, preparing an efficient cathode is necessary to address the challenges such as poor catalytic activity and CO2 poisoning. Herein, an efficient optimized strategy for designing a high-performance cathode is demonstrated. By motivating the phase transformation of BaFeO3-δ perovskites, achieved by doping Pr at the B site, remarkably enhanced electrochemical activity and CO2 resistance are thus achieved. The appropriate content of Pr substitution at Fe sites increases the oxygen vacancy concentration of the material, promotes the reaction on the oxygen electrode, and shows excellent electrochemical performance and efficient catalytic activity. The improved reaction kinetics of the BaFe0.95Pr0.05O3-δ (BFP05) cathode is also reflected by a lower electrochemical impedance value (0.061 Ω·cm2 at 750 °C) and activation energy, which is attributed to high surface oxygen exchange and chemical bulk diffusion. The single cells with the BFP05 cathode achieve a peak power density of 798.7 mW·cm-2 at 750 °C and a stability over 50 h with no observed performance degradation in CO2-containing gas. In conclusion, these results represent a promising optimized strategy in developing electrode materials of IT-SOFCs.

Pt modulates the electronic structure of Pd to improve the performance of Pd-based catalytic combustion catalyst

The electronic modulation between the catalytic active components can improve the catalytic activity and stability of the catalyst. The Pd-based catalysts can easily react with SOX to form stable and inactive sulfates. In this paper, the Pd–Pt-based catalytic combustion catalyst was prepared by replacing part of Pd with a small amount of Pt. The storage tank VOCs catalytic combustion activity and the anti-SO2 poisoning performance of the Pd–Pt-based catalyst and Pd-based catalyst were tested. The Pd 3d binding energy of each Pd-based catalyst was detected by XPS characterization, and the electronic structure changes of Pd active components was analyzed by the change of Pd 3d binding energy. The effect of electrons transfer between Pd and Pt on the improvement of catalytic combustion activity and SO2 poisoning resistance of Pd-based catalysts was analyzed. The results show that the Pt addition can increase the electron cloud density of the Pd active components, and improve the performance of the Pd active components to adsorb and activate oxygen. The reaction of Pd and SOX to form sulfate needs to gain electrons. The increase in the electron cloud density of the Pd active components in Pd–Pt-based catalyst makes it difficult for the Pd active components to adsorb SOX and difficult to react with SOX to form sulfate, thereby preventing the Pd active components from being poisoned and deactivated.

Molybdenum compound cocatalyzed Ni‐based anode electrocatalysts for EOR in alkaline media

In this study, Mo2C and MoS2 were used as cocatalyst for a non-noble metal for the first time for ethanol electro-oxidation reaction (EOR) in alkaline media. Anode electrocatalysts containing Nickel, Mo compound, and carbon support were synthesized at different weight ratios of Ni and Mo2C (or MoS2) while keeping the carbon support weight constant in each catalyst combination to investigate the best weight ratio among our range. Physical characterizations of the electrocatalysts were investigated by XRD, XPS, SEM-EDS, EDAX, and TEM techniques. Electrochemical performance of the catalysts was studied via cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronoamperometry (CA) by using a home-made electrochemical cell test system exhibiting similar alkaline direct ethanol fuel cell (ADEFC) architecture by giving the opportunity of using an anion exchange membrane. All of the Ni-Mo2C/C and Ni-MoS2/C at different weight ratios were shown better performance than pristine Ni and Ni/C. The highest current density was measured with Ni-Mo2C/C-2 (11.4 mA cm−2) anode catalyst, which exhibits the highest electrochemical reaction rate. The diffusion coefficient of the catalysts was calculated by using the data from linear LSV. CA experiment results showed that the tolerance for catalytic poisoning and durability of Ni-Mo2C/C-2 was better among all the electrocatalysts. Highlights Literature survey showed that Mo2C and MoS2 are promising co-catalysts for EOR. However, there is a lack of study on the use of Mo2C or MoS2 as co-catalyst with a non-noble metal. Molybdenum compound containing transition metal-based anode electro-catalysts were synthesized for EOR in alkaline media. A home-made electrochemical cell is designed to make the system more similar to an ADEFC system. The results of the electrochemical characterizations are showed that the Mo compound addition increased the catalytic activity and stability.

Theoretical Study of the Catalytic Activity and Anti-SO2 Poisoning of a MoO3/V2O5 Selective Catalytic Reduction Catalyst.

In this paper, density functional theory has been applied to study the mechanism of anti-SO2 poisoning and selective catalytic reduction (SCR) reaction on a MoO3/V2O5 surface. According to the calculation results, the SO2 molecule can be converted into SO3 on V2O5(010) and further transformed into NH4HSO4, which poisons V2O5. If V2O5 and MoO3 are combined with each other, charge separation of V2O5 and MoO3, which are negatively and positively charged, respectively, occurs at the interface. In ammonium bisulfate liquid droplets on the MoO3/V2O5 surface, NH4+ tends to adhere to the V2O5(010) surface and can be removed through the SCR reaction and HSO4– tends to adhere to the MoO3(100) surface and can be resolved into SO3 and H2O, which can be released into the gas phase. Thus, MoO3/V2O5 materials are resistant to SO2 poisoning. In the MoO3/V2O5 material, Brønsted acid sites are easily formed on the negatively charged V2O5(010) surface; this reduces the energy barrier of the NH3 dissociation step in the NH3-SCR process and further improves the catalytic activity.

Photocatalytic conversion of biomass-based monosaccharides to lactic acid by ultrathin porous oxygen doped carbon nitride

Application of photocatalysis to biorefinery conforms to the requirement of sustainable development of the society. It is of great significance, yet limited success has been achieved. Here, we report oxygen atom doped on the ultrathin porous carbon nitride (Ut-OCN) as an efficient photocatalyst for lactic acid production. The Ut-OCN photocatalyst represents an increase in the absorption range of visible-light via tunable band structure. Remarkably, the photocatalyst exhibited effective activity with lactic acid yield above 89.7 %, and this system is universal for the synthesis of lactic acid from biomass-based monosaccharides. Catalytic poisoning and recycling experiments revealed that the selectivity of ·O2− is superior to ·OH, 1O2, h+ in proper order. The photocatalyst is highly stable and recyclable. Moreover, the yield of lactic acid of one-thousand-fold scale-up experiment irradiated by sunlight retained 98.4 % of one-time experiment. It is believed that this work paves a way for the lactic acid production via photocatalysis.