Catalyst Design Concept Research Articles

Electron transfer from yttrium hydride to Mo-carbonitride boosts low-temperature ammonia synthesis

Ammonia is pivotal to various chemical industries, which is produced using the Haber-Bosch process. This process requires harsh conditions (e.g., 20.0 MPa and (500–600)°C) to generate ammonia and thus, is an energy intensive process. The growing consensus is to mild the conditions for ammonia generation. Herein, we demonstrate the use of hydride to increase the activity of molybdenum carbonitride (MCN). YH@MCN (95:5, w/w) generates ammonia at a rate of 448μmolg−1h−1 at 255 °C and 0.1 MPa. To address the stability issue of hydride, we incorporate iron. The experiment demonstrates two-fold rates for such catalyst, comparing MCN alone. The activation energy (19.73kJmol-1) for YFeH@MCN is considerably low, owing to the electron transfer from YH to MCN that facilitates nitrogen dissociation. Hence, the use of distinct sites for easy dissociation of nitrogen molecules, and the synergy between them, results in an activity that exceeds of conventional molybdenum and iron-based catalysts, and is comparable to ruthenium-based catalysts. Our results illustrate the potential of using synergistic multiple active sites in catalysts, and introduce a design concept for ammonia synthesis catalysts, using readily available elements.

A novel high-entropy spinel ferrites (CoNiCuZnMg)Fe2O4 catalyst for H2 production via steam reforming of derived volatiles from polypropylene and waste cooking oil

Municipal organic waste conversion to high-value products is a vital carbon–neutral way to simultaneously tackle the energy crisis and environmental contamination. This study aims to develop and evaluate a novel high-entropy spinel ferrites (Co0.2Ni0.2Cu0.2Zn0.2Mg0.2)Fe2O4 catalyst (HEO) toward H2 production from co-pyrolysis volatiles of polypropylene (PP) and waste cooking oil (WCO) in an integrated two-stage reactor system. In the 1st stage of medium temperature reforming, the optimal 3:7 PP/WCO blend mass ratio facilitated H2 production. Under a catalytic reforming at high temperature of 750 °C in the 2nd stage, the HEO catalyst demonstrated remarkable efficiency, yielding 58.43 mmol·g−1 of H2 with a composition of 65.17 %, a notable 22.3 times higher than that without HEO. The catalyst exhibited a prolonged service life of 540 min without compromising H2 selectivity, maintaining a high yield of 510.2 mmol·gcat.−1·s−1. The exceptional performance of HEO arises from the synergistic effects of multiple elements, augments oxygen vacancy, enhances reducibility, and promotes structural stability in the high-entropy system, which causes the strong C–C breaking ability and the excellent C–H breaking abilities of Fe, Ni, Co, Cu, and Zn species. The analysis of tar, gaseous products, and deactivated HEO catalyst characterization results provides a comprehensive understanding of the co-pyrolysis route and volatiles catalytic reforming process. This study developed a high-entropy ferrite catalyst that not only achieves efficient and stable H2 production but also lays the foundation for a new high-entropy catalyst design concept, fostering the development of efficient reforming catalysts for H2 production.

Supported Ruthenium catalysts with electronic effect and acidity-basicity for efficient reductive amination of biomass-based carbonyl compounds

The efficiently reductive amination of carbonyl compounds to the corresponding primary amines under mild condition with NH3 and H2 as nitrogen and hydrogen sources is a challenging task in the chemistry community. Therefore, supported Ru catalysts with excellent catalytic activity for reductive amination of carbonyl compounds were synthesized in this work using a simple impregnation method. Among them, Ru/SBA-15 showed excellent catalytic performance for reductive amination of carbonyl compounds, and the yields were more than 91%. The Ru nanoparticles (Ru NPs) were uniformly dispersed on the support, and the structure of the support was not destroyed. The acidity-basicity and the appropriate electron density are the reasons for the high activity and selectivity of supported Ru catalysts. The catalyst design concept with both electronic effect and acidity-basicity combination provides a new strategy for the conversion of biomass-based carbonyl compounds.

N/S co-doped Nb2CTx MXene as the effective catalyst for improving the hydrogen storage performance of MgH2

While MgH2 has high hydrogen storage capacity, its high dehydrogenation temperature and sluggish de-/hydrogenation rate have hindered practical application. In the present work, a non-metallic element (N, S) co-doped Nb2CTx MXene catalyst (N/S-Nb2CTx) is employed to improve the hydrogen storage property of MgH2. The dehydrogenation activation energy of MgH2+N/S-Nb2CTx composite is reduced to 70.00 kJ mol–1 H2, which is much lower than that of MgH2+Nb2CTx (99.44 kJ mol–1 H2) and Milled-MgH2 (133.19 kJ mol–1 H2). The composite can release about 4.78 wt% of H2 within 30 min at 225 °C and uptake about 4.00 wt% of H2 within 80 min even at 30 °C under 30 bar H2, which is significantly better than most of the reported MgH2+Nb-based-catalyst composites. The mechanism analysis reveals that the stable layered structure of the N/S-Nb2CTx catalyst provides enough nucleation sites for MgH2/Mg, and the in-situ formed substances (Nb, NbO2) play the role of elongating Mg–H bond. Besides, the N, S co-doped effectively enhances the ability of multivalent Nb elements to promote the electron transfer between Mg2+ and H–, and it promotes the diffusion of hydrogen through weakening the interaction between Nb and H atoms, thus the de-/hydrogenation kinetics and cyclic stability of MgH2 is significantly improved. This work not only proves that Nb2CTx can effectively enhance its catalytic activity by N and S co-doping, but also provides a MXene-based catalyst design concept for highly efficient hydrogen storage catalysts.

Highly Durable and Active Electrocatalysts Using Pt Nanorod Catalysts Supported on Nb Doped SnO2 for Polymer Electrolyte Fuel Cells Operating at Wide Temperature Range

The improvement of the durability and activity in cathode catalyst is required toward the wide spread use of polymer electrolyte fuel cells. One of the interesting catalysts is the Pt catalysts supported on SnO2 (Pt/M-SnO2, M = Nb, Ta) without carbon additives [1,2]. The durability (startup/shutdown, load cycling) and oxygen reduction reaction (ORR) activity of the Pt/M-SnO2 is superior to those of commercial Pt catalysts supported on carbon black (Pt/CB) etc. [3-8]. The non-carbon support of M-SnO2 nanoparticles has a unique carbon-like microstructure of a fused-aggregate network structure, which supply the essential function of the electronically constructing pathways via necking of each support particles and the gas diffusion pathways via the open pores surrounded by particles. The Pt nanorod catalyst on M-SnO2 also improves the ORR activity as shown in the catalyst design concept (Fig. 1)[9]. The IV performance of the single cell using the Pt nanorod/Nb-SnO2 cathode catalyst layers at operating temperatures from 80oC to 120oC is quite high to approach the NEDO target performance (Fig. 2) with keeping high durability. The catalyst is considered to have possibilities for application of the heavy-duty vehicles operating at wide-temperature range (< 120oC)[10]. Acknowledgments This work was partially supported by funds for the project “Electrolytes, Catalysts and Catalyst layers with Extraordinary Efficiency, power and Durability for PEFCs-2030 (ECCEED’30) from the New Energy and Industrial Technology Development Organization (NEDO) of Japan, and JSPS KAKENHI Grant Number (23H02059) from the Ministry of Education, Culture, Sports, Science and Technology. References A. Masao, S. Noda, F. Takasaki, K. Ito, K. Sasaki, Electrochem. Solid-State Lett.,12, B119 (2009).E. Fabbri, A. Rabis, R. Kötz, T.J. Schmidt, Phys. Chem. Chem. Phys., 16, 13672 (2014).K. Kakinuma, M. Uchida, T. Kamino, H. Uchida, M. Watanabe, Electrochim. Acta, 56, 2881 (2011).Y. Senoo, K. Kakinuma, M. Uchida, H. Uchida, S. Deki, M. Watanabe, RSC Adv., 6, 321800 (2014).Y. Chino, K. Taniguchi, Y. Senoo, K. Kakinuma, M. Watanabe, M. Uchida, J. Electrochem. Soc., 162, F736 (2015).K. Kakinuma, R. Kobayashi, A. Iiyama, M. Uchida, J. Electrochem. Soc., 165, J3083 (2018).K. Kakinuma, K. Suda, R. Kobayashi, T. Tano, C. Arata, I. Amemiya, S. Watanabe, M. Matsumoto, H. Imai, A. Iiyama, M. Uchida, ACS Appl. Mater. Interfaces 11, 34957 (2019).K. Kakinuma, M. Hayashi, T. Hashimoto, A. Iiyama, M. Uchida, ACS Appl. Energy Mater., 3, 6922 (2020).G. Shi, T. Tano, D.A. Tryk, A. Iiyama, M. Uchida, K.Kakinuma, ACS Catal., 11, 5222 (2021).K. Kakinuma, H. Taniguchi, T. Asakawa, T. Miyao, M. Uchida, Y. Aoki, T. Akiyama, A. Masuda, N. Sato, A. Iiyama J. Electrochem. Soc. 169 (2022) 044522. Figure 1

Tuning the Crystal Phase to Form MnGaOx -Spinel for Highly Efficient Syngas to Light Olefins.

The oxide-zeolite (OXZEO) catalyst design concept has been demonstrated in an increasing number of studies as an alternative avenue for direct syngas conversion to light olefins. We report that face-centered cubic (FCC) MnGaOx -Spinel gives 40 % CO conversion, 81 % light olefins selectivity, and a 0.17 g gcat -1 h-1 space-time yield of light olefins in combination with SAPO-18. In comparison, solid solution MnGaOx (characterized by Mn-doped hexagonal close-packed (HCP) Ga2 O3 ) with a similar chemical composition gives a much inferior activity, i.e., the specific surface activity is one order of magnitude lower than the spinel oxide. Photoluminescence (PL), in situ Fourier-transform infrared (FT-IR), and density functional theory (DFT) calculations indicate that the superior activity of MnGaOx -Spinel can be attributed to its higher reducibility (higher concentration of oxygen vacancies) and the presence of coordinatively unsaturated Ga3+ sites, which facilitates the dissociation of the C-O bond via a more efficient ketene-acetate pathway to light olefins.

Tuning the Crystal Phase to Form MnGaOx‐Spinel for Highly Efficient Syngas to Light Olefins

AbstractThe oxide–zeolite (OXZEO) catalyst design concept has been demonstrated in an increasing number of studies as an alternative avenue for direct syngas conversion to light olefins. We report that face‐centered cubic (FCC) MnGaOx‐Spinel gives 40 % CO conversion, 81 % light olefins selectivity, and a 0.17 g gcat−1 h−1 space‐time yield of light olefins in combination with SAPO‐18. In comparison, solid solution MnGaOx (characterized by Mn‐doped hexagonal close‐packed (HCP) Ga2O3) with a similar chemical composition gives a much inferior activity, i.e., the specific surface activity is one order of magnitude lower than the spinel oxide. Photoluminescence (PL), in situ Fourier‐transform infrared (FT‐IR), and density functional theory (DFT) calculations indicate that the superior activity of MnGaOx‐Spinel can be attributed to its higher reducibility (higher concentration of oxygen vacancies) and the presence of coordinatively unsaturated Ga3+ sites, which facilitates the dissociation of the C−O bond via a more efficient ketene–acetate pathway to light olefins.

Surface Engineering of Titania Boosts Electroassisted Propane Dehydrogenation at Low Temperature.

Electric field catalysis using surface proton conduction, in which proton hopping and collision on the reactant are promoted by external electricity, is a promising approach to break the thermodynamic equilibrium limitation in endothermic propane dehydrogenation (PDH). This study proposes a catalyst design concept for more efficient electroassisted PDH at low temperature. Sm was doped into the anatase TiO2 surface to increase surface proton density by charge compensation. Pt-In alloy was deposited on the Sm-doped TiO2 for more favorable proton collision and selective propylene formation. The catalytic activity in electroassisted PDH drastically increased by doping an appropriate amount of Sm (1 mol % to Ti) where the highest propylene yield of 19.3 % was obtained at 300 °C where the thermodynamic equilibrium yield was only 0.5 %. Results show that surface proton enrichment boosts alkane dehydrogenation at low temperature.

Surface Engineering of Titania Boosts Electroassisted Propane Dehydrogenation at Low Temperature

AbstractElectric field catalysis using surface proton conduction, in which proton hopping and collision on the reactant are promoted by external electricity, is a promising approach to break the thermodynamic equilibrium limitation in endothermic propane dehydrogenation (PDH). This study proposes a catalyst design concept for more efficient electroassisted PDH at low temperature. Sm was doped into the anatase TiO2 surface to increase surface proton density by charge compensation. Pt−In alloy was deposited on the Sm‐doped TiO2 for more favorable proton collision and selective propylene formation. The catalytic activity in electroassisted PDH drastically increased by doping an appropriate amount of Sm (1 mol % to Ti) where the highest propylene yield of 19.3 % was obtained at 300 °C where the thermodynamic equilibrium yield was only 0.5 %. Results show that surface proton enrichment boosts alkane dehydrogenation at low temperature.

Processing renewable and waste-based feedstocks with fluid catalytic cracking: Impact on catalytic performance and considerations for improved catalyst design.

Refiners around the globe are either considering or are actively replacing a portion of their crude oil inputs originating from fossil sources with alternative sources, including recycled materials (plastics, urban waste, mixed solid waste) and renewable materials (bio-mass waste, vegetable oils). In this paper, we explore such replacement, specifically focusing on the fluid catalytic cracking (FCC) operation. Five pyrolysis oils, obtained from municipal solid waste (MSW) and biogenic material (olive stones/pits), were fully characterized and tested at 10% loading against a standard fluid catalytic cracking (FCC) vacuum gasoil (VGO) feed in a bench scale reactor using an industrially available fluid catalytic cracking catalyst based on ultrastable Y zeolite to simulate fluid catalytic cracking co-processing. Despite having unique feed properties, including high Conradson carbon (e.g., up to 19.41wt%), water (e.g., up to 5.7wt%), and contaminants (e.g., up to 227ppm Cl) in some cases, the five pyrolysis oils gave similar yield patterns as vacuum gasoil. Gasoline was slightly (ca. 1wt%) higher in all cases and LPG slightly (ca. 1wt%) lower. Olefinicity in the LPG streams were unchanged, bottoms and light cycle oil (LCO) showed no significant changes, while dry gas was slightly (up to -0.2wt%) lower. Coke selectivity was also unchanged (maximum -7.7wt%, relatively), suggesting minimal to no heat balance concerns when co-processing in an industrial fluid catalytic cracking unit. The results demonstrate the applicability of municipal solid waste and biogenic originating pyrolysis oils into a refinery. A catalyst design concept is explored, based on higher rare Earth oxide exchange and/or utilization of ZSM-5 zeolite, that would further minimize the impacts of replacing fossil oils with pyrolysis oils, namely one that shifts the 1% higher gasoline into LPG.

CoW Bimetallic Carbide Nanocatalysts: Computational Exploration, Confined Disassembly-Assembly Synthesis and Alkaline/Seawater Hydrogen Evolution.

Earth-abundant tungsten carbide exhibits potential hydrogen evolution reaction (HER) catalytic activity owing to its Pt-like d-band electronic structure, which, unfortunately, suffers from the relatively strong tungsten-hydrogen binding, deteriorating its HER performance. Herein, a catalyst design concept of incorporating late transition metal into early transition metal carbide is proposed for regulating the metal-H bonding strength and largely enhancing the HER performance, which is employed to synthesize CoW bi-metallic carbide Co6 W6 C by a "disassembly-assembly" approach in a confined environment. Such synthesized Co6 W6 C nanocatalyst features the optimal Gibbs free energy of *H intermediate and dissociation barrier energy of H2 O molecules as well by taking advantage of the electron complementary effect between Co and W species, which endows the electrocatalyst with excellent HER performance in both alkaline and seawater/alkaline electrolytes featuring especially low overpotentials, elevated current densities, and much-enhanced operation durability in comparison to commercial Pt/C catalyst. Moreover, a proof-of-concept Mg/seawater battery equipped with Co6 W6 C-2-600 as cathode offers a peak power density of 9.1mW cm-2 and an open-circuit voltage of ≈1.71V, concurrently realizing hydrogen production and electricity output.

Highly Durable and Active Electrocatalysts Using Pt Nanorod Catalysts Supported on Nb Doped SnO2 for Polymer Electrolyte Fuel Cells

In proton exchange membrane fuel cells (PEMFCs) operating with the use of Pt/carbon (Pt/C) cathode catalysts, severe corrosion of the carbon support has been recognized at high potentials. The improvement of the catalyst durability with high activity is required for heavy use applications. Alternative candidate catalysts with high durability and high activity are Pt catalysts supported on non-carbon ceramic supports [1,2]. Our group confirmed that Pt catalysts supported on SnO2 (Pt/M-SnO2, M = Nb, Ta) without carbon additive were superior in durability (startup/shutdown, load cycling) and oxygen reduction reaction (ORR) activity to those of commercial Pt catalysts, e.g., supported on either graphitized carbon black (Pt/GCB, TEC10EA30E, TKK) or carbon black (Pt/CB, TEC10E50E, TKK), by evaluation of membrane-electrode assemblies (MEA) [3-9]. The non-carbon support of SnO2 nanoparticles has a unique carbon-like microstructure consisting of a fused-aggregate network structure, which enhances the electronically conducting pathways via the aggregated microstructure and gas diffusion pathways via the open pores in the microstructure. We have also proposed ways to design the Pt nanorod supported on the Nb-SnO2 based on the catalyst design concept (Fig. 1)[10]. The cell performance using the Pt/SnO2 cathode catalyst layers at operating temperatures from 80oC to 120oC is quite promising for the development of high-power density (Fig. 2) with simultaneous high durability. Acknowledgments This work was partially supported by funds for the project “Electrolytes, Catalysts and Catalyst layers with Extraordinary Efficiency, power and Durability for PEFCs-2030 (ECCEED’30) from the New Energy and Industrial Technology Development Organization (NEDO) of Japan, and JSPS KAKENHI Grant Number (20H02839) from the Ministry of Education, Culture, Sports, Science and Technology. References A. Masao, S. Noda, F. Takasaki, K. Ito, K. Sasaki, Electrochem. Solid-State Lett., 12, B119 (2009).E. Fabbri, A. Rabis, R. Kötz, T.J. Schmidt, Phys. Chem. Chem. Phys., 16, 13672 (2014).K. Kakinuma, M. Uchida, T. Kamino, H. Uchida, M. Watanabe, Electrochim. Acta, 56, 2881 (2011).Y. Senoo, K. Kakinuma, M. Uchida, H. Uchida, S. Deki, M. Watanabe, RSC Adv., 6, 321800 (2014).Y. Chino, K. Taniguchi, Y. Senoo, K. Kakinuma, M. Watanabe, M. Uchida, J. Electrochem. Soc., 162, F736 (2015).K. Kakinuma, R. Kobayashi, A. Iiyama, M. Uchida, J. Electrochem. Soc., 165, J3083 (2018).K. Kakinuma, K. Suda, R. Kobayashi, T. Tano, C. Arata, I. Amemiya, S. Watanabe, M. Matsumoto, H. Imai,Iiyama, M. Uchida, ACS Appl. Mater. Interfaces 11, 34957 (2019).K. Kakinuma, M. Hayashi, T. Hashimoto, A. Iiyama, M. Uchida, ACS Appl. Energy Mater., 3, 6922 (2020).G. Shi, T. Tano, D.A. Tryk, A. Iiyama, M. Uchida, K.Kakinuma, ACS Catal., 11, 5222 (2021). Figure 1

High-entropy intermetallics on ceria as efficient catalysts for the oxidative dehydrogenation of propane using CO2

The oxidative dehydrogenation of propane using CO2 (CO2-ODP) is a promising technique for high-yield propylene production and CO2 utilization. The development of a highly efficient catalyst for CO2-ODP is of great interest and benefit to the chemical industry as well as net zero emissions. Here, we report a unique catalyst material and design concept based on high-entropy intermetallics for this challenging chemistry. A senary (PtCoNi)(SnInGa) catalyst supported on CeO2 with a PtSn intermetallic structure exhibits a considerably higher catalytic activity, C3H6 selectivity, long-term stability, and CO2 utilization efficiency at 600 °C than previously reported. Multi-metallization of the Pt and Sn sites by Co/Ni and In/Ga, respectively, greatly enhances propylene selectivity, CO2 activation ability, thermal stability, and regenerable ability. The results obtained in this study can promote carbon-neutralization of industrial processes for light alkane conversion.

Initial catalytic behavior of chromium oxide during induction period of fluidized dehydrogenation of propane

Fluidized-bed propane dehydrogenation (PDH) has the advantage being energy efficient; however a new catalyst-design concept that overcomes short reaction time is required. While Pt and Cr are excellent catalysts for PDH, the formation of propylene is delayed for a few seconds due to the formation of CH4, CO and CO2. To better understand this induction period, we developed a reaction system for monitoring products on the second timescale and an analytical method (TPO) for distinguishing different oxygen species that develop over the Cr/Al2O3. A detailed correlation between the initial selectivity to propylene and the formation of oxygen species on a chromium-alumina catalyst was established by O2-TPO and Raman analysis. The properties of the oxygen species were found to depend on the degree of redox catalyst dispersion, and that lattice oxygen accumulated over the monolayer results in an oxidation reaction that is responsible for the induction period. We also introduce a catalyst-development strategy for fluidization process that reduces the induction period by control of oxygen species on catalyst and increases propylene selectivity within 3 s of the commencement of the reaction.

Catalytic coupling of CO2 and epoxides by lignin-based catalysts: A combined experimental and theoretical study

A new strategy for the construction of an amine-modified lignin has been developed through the Mannich reaction. The lignin-based catalyst, (PEI(70000)-SL/ZnBr2), acted as a green and reusable heterogeneous catalyst for the catalytic conversion of CO2 and epoxides into cyclic carbonates. This catalyst exhibited excellent conversion and selectivity in the CO2 cycloaddition reaction due to the synergistic effects of the hydroxyls (-OH) and metal (Zn2+) as Lewis acid sites, and organic amines (-NH2) and halogen anions (Br-) as nucleophiles. Some lignin model compounds were used to study the relationship between structure and activity in order to evaluate the synergistic effects during the cycloaddition reaction. Functional groups, such as Zn2+, -OH and -NH2, in adjacent positions of the lignin-based catalyst yielded the cyclic carbonates in high efficiencies and selectivities. Furthermore, DFT calculation and the experimental results revealed that Zn2+ enhanced the ring-opening process via SN1 mechanism, with the energy barrier of the ring-opening process of 18.9 kcal mol-1 due to the cooperation of the Zn2+ with phenolic hydroxyl groups. These findings do not only provide a novel design concept for biomass-based catalysts but also accomplished the transformation of CO2 into valuable products.

Coordination confinement pyrolysis to Flower-like nanocomposites composed of ultrathin nanosheets with embedded ultrasmall CoP nanoparticles for overall water splitting

Electrocatalytic water splitting is being widely studied to produce low-cost and clean fuels for energy saving and conversion. However, the development of efficient and stable electrocatalysts remains a huge challenge. In this study, a novel coordination confinement pyrolysis method was demonstrated to construct an efficient bifunctional electrocatalyst with inherited hierarchical flower-like morphology, in which the ultra-small CoP nanoparticles with ca. 4 nm in size were successfully embedded into the nanosheet assembly unit. The resulted catalyst product with a unique three-dimensional structure not only realizes the satisfying catalytic efficiencies with overpotentials of 143 and 298 mV for HER and OER at the current density of 10 mA·cm−2, but also delivers suitable stability after long-term electrolytic process. Therefore, this catalyst design concept integrating ultra-small nanoparticles, ultra-thin nanosheets, and three-dimensional assembly could provide a novel idea to evolve the other heterogeneous catalysts.

Co/MoC Nanoparticles Embedded in Carbon Nanoboxes as Robust Trifunctional Electrocatalysts for a Zn-Air Battery and Water Electrocatalysis.

To meet the application needs of rechargeable Zn-air battery and electrocatalytic overall water splitting (EOWS), developing high-efficiency, cost-effective, and durable trifunctional catalysts for the hydrogen evolution reaction (HER), oxygen evolution, and reduction reaction (OER and ORR) is extremely paramount yet challenging. Herein, the interface engineering concept and nanoscale hollowing design were proposed to fabricate N-doping carbon nanoboxes confined with Co/MoC nanoparticles. Uniform zeolitic imidazolate framework nanocube was employed as the starting material to construct the trifunctional electrocatalyst through the conformal polydopamine-Mo layer coating and the subsequent pyrolysis treatment. The Co@IC/MoC@PC catalyst displayed superior electrochemical ORR performances with a positive half-wave potential of 0.875 V and a high limiting current density of 5.89 mA/cm2. When practically employed as an electrocatalyst in regenerative Zn-air battery, a high specific capacity of 728 mAh/g, a large peak power density of 221 mW/cm2, a high open-circuit voltage of 1.482 V, and a low charge/discharge voltage gap of 0.41 V were obtained. Moreover, its practicability was further exploited by overall water splitting, affording low overpotentials of 277 and 68 mV at 10 mA/cm2 for the OER and HER in 1 M KOH solution, respectively, and a decent operating potential of 1.57 V for EOWS. Ultraviolet photoelectron spectroscopy and density functional theory calculation revealed that the Co/MoC interface synergistically facilitated the charge-transfer, thereby contributing to the enhancements of electrocatalytic ORR/OER/HER processes. More importantly, this catalyst design concept can offer some interesting prospects for the construction of outstanding trifunctional catalysts toward various energy conversion and storage devices.

Doubly Decorated Platinum–Gallium Intermetallics as Stable Catalysts for Propane Dehydrogenation

AbstractPropane dehydrogenation (PDH) is a promising chemical process that can satisfy the increasing global demand for propylene. However, the Pt‐based catalysts that have been reported thus far are typically deactivated at ≥600 °C by side reactions and coke formation. Thus, such catalysts possess an insufficient life. Herein, we report a novel catalyst design concept, namely, the double decoration of PtGa intermetallics by Pb and Ca, which synergize the geometric and electronic promotion effects on the catalyst stability, respectively. Pb is deposited on the three‐fold Pt3 sites of the PtGa nanoparticles to block them, whereas Ca, which affords an electron‐enriched single‐atom‐like Pt1 site, is placed around the nanoparticles. Thus, PtGa−Ca−Pb/SiO2 exhibits an outstandingly high catalytic stability, even at 600 °C (kd=0.00033 h−1, τ=3067 h), and almost no deactivation of the catalyst was observed for up to 1 month for the first time.

Doubly Decorated Platinum-Gallium Intermetallics as Stable Catalysts for Propane Dehydrogenation.

Propane dehydrogenation (PDH) is a promising chemical process that can satisfy the increasing global demand for propylene. However, the Pt-based catalysts that have been reported thus far are typically deactivated at ≥600 °C by side reactions and coke formation. Thus, such catalysts possess an insufficient life. Herein, we report a novel catalyst design concept, namely, the double decoration of PtGa intermetallics by Pb and Ca, which synergize the geometric and electronic promotion effects on the catalyst stability, respectively. Pb is deposited on the three-fold Pt3 sites of the PtGa nanoparticles to block them, whereas Ca, which affords an electron-enriched single-atom-like Pt1 site, is placed around the nanoparticles. Thus, PtGa-Ca-Pb/SiO2 exhibits an outstandingly high catalytic stability, even at 600 °C (kd =0.00033 h-1 , τ=3067 h), and almost no deactivation of the catalyst was observed for up to 1 month for the first time.

Oxide–Zeolite-Based Composite Catalyst Concept That Enables Syngas Chemistry beyond Fischer–Tropsch Synthesis

Syngas chemistry has been under study since Fischer-Tropsch synthesis (FTS) was invented in the 1920s. Despite the successful applications of FTS as the core technology of coal-to-liquid and gas-to-liquid processes in industry, the product selectivity control of syngas conversion still remains a great challenge, particularly for value-added chemicals such as light olefins. Recent studies show that the catalyst design concept of OXZEO (oxide-zeolite-based composite) enables direct syngas conversion to mixed light olefins with a selectivity reaching 80% and to ethylene with a selectivity of 83% among hydrocarbons. They both well-surpass the limits predicated by the Anderson-Schultz-Flory model via the conventional FTS route (58% and 30%, respectively). Furthermore, this catalyst concept allows one-step synthesis of gasoline-range isoparaffins and aromatic compounds, which is otherwise not possible in conventional FTS. A rapidly growing number of studies demonstrate the versatility of this concept and may form a technology platform for utilization of carbon resources including coal, natural gas, and biomass via syngas to a variety of basic chemicals and fuels. However, the selectivity control mechanism is far from being understood. Therefore, we focus mainly on the catalytic roles of the bifunctionalities of OXZEO while reviewing the development of bifunctional catalysts for selective syngas conversion by taking syngas-to-light olefins as an example. With this, we intend to provide insights into the selectivity control mechanism of the OXZEO concept in order to understand the challenges and prospects for future development of much more active and more selective catalysts.