查看更多>>摘要：Low electrical conductivity and poor accessibility of MoS2 reaction sites raise great challenges in maximizing the triple-phase-boundary (TPB) sites of MoS2-based electrodes and minimizing ohmic losses for efficient hydrogen evolution reaction (HER) in practical proton exchange membrane (PEM) water electrolysis. Herein, we report a scalable hydrothermal approach to fabricate ionomer-free integrated electrodes with engineered 1T-2 H heterophase and defect-rich MoS2 nanosheets (MoS2NSS) in-situ grown onto the carbon fiber paper (CFP). With an ultralow loading of 0.14 mg/cm2, a small voltage of 2.25 V was obtained at 2000 mA/cm~2 in a practical cell with Nafionll5 membrane, which outperforms all previously reported high-loading non-precious catalyst-based electrodes. Impressively, it shows 44 times higher mass activity than a high-loading and ionomer-mixed MoS2 assemblies electrode. This work builds a bridge from catalyst optimization to electrode fabrication and provides a promising direction for improving intrinsic catalytic activity, electrode conductivity and stability for practical PEM water electrolysis.
查看更多>>摘要：Poly(ionic liquid)-metal (PIL-metal) hybrids were developed as a platform for facilely constructing tandem catalysts to reach highly efficient electrocatalytic reduction of CO2 (CO2RR). By introducing extra metal with distinct CO2RR response to Cu-PIL hybrids, Cu@PIL@Ag and Cu@PIL@Bi were obtained. Remarkably, Cu@PIL@Ag exhibits an excellent C_(2+) Faradaic efficiency (FE_(C2+)) of 83.2% with a high partial current density (j_(C2+)) of 416.1 mA cm~(-2) in 3 M KOH and an even higher j_(C2+) (708.9 mA cm~(-2)) in 1 M KOH, while Cu@PIL@Bi possesses high FE_(C1) (>60%) and low FE_(C2+) (< 5%) in a wide potential range. Mechanistic studies demonstrate the output of such a tandem system, either synergistic or maladjusted, depends on not only CO2RR response of Ag and Bi but also specific Cu-Ag and Cu-Bi interactions. Besides, the PIL layer could adjust the reactivity by promoting the dispersion and availability of active sites and enriching the local key intermediates.
查看更多>>摘要：Oily wastewater from solvent extraction is hard to be treated due to a large number of organic pollutants and high salt content. Here, we found a photocatalyst (natural sphalerite (NS), (Zn, Fe)S)) with great application potential for treating oily wastewater of solvent extraction, and studied its application in removal organics from actual solvent extraction wastewater of spent lithium-ion battery recycling. It found that doping Fe participated in the formation of new energy bands and accepted transferred-electrons from ZnS as electron acceptor, thus enhanced the visible-light absorption ability and carrier mobility. The photo catalysis activity of NS was further improved by adding hydrogen peroxide (H2O2), mainly because it prevented the recombination of photo-generated electron-hole pairs. Consequently, 86.20% removal of total organic carbon was achieved with H2O2-assisted NS under the optimum conditions. This work is expected to shed light on the application of photocatalysis in treatment of oily wastewater of solvent extraction.
查看更多>>摘要：H2O2 has been widely used as a green oxidant in many heterogeneous reactions. However, its disproportionation accelerated by either Bronsted acid (BA) or redox metal sites often results in low H2O2 utilization. Given this, metals less able to redox have been used because the formation of surface metal-peroxo species exhibits a certain degree of selectivity towards substrates. However, those catalysts often bear BA sites on their surface for charge balance, making it imperative to study H2O2 activation pathway in the presence of both sites. Herein, layered HNb3O8 with structurally preserved BA sites was used for this purpose. We found that the exposure of Nb sites via bulk-to-nano regulation of this material hinders H2O2 disproportionation promoted by BA sites. Among various Nb-peroxo species, its bidentate configuration formed on highly distorted NbOx was found to provide the best reactivity in alkene epoxidation with a near stoichiometric H2O2 utilization.
查看更多>>摘要：The realization of efficient and fully controllable synthesis of single atom catalysts is an exciting frontier, yet still challenging in the modern catalysis field. Here we describe a straightforward high-temperature quenching approach to precisely construct isolated palladium atoms supported over cubic indium oxide, with individual palladium atoms coordinated with four neighboring oxygen atoms. This palladium catalyst achieves exceptional catalytic efficiency in the selective hydrogenation of nitrobenzene to aniline, with more than 99% chemoselectivity under almost 100% conversion. Moreover, it delivers excellent recyclability, anti-CO poisoning ability, storage stability, and substrate tolerance. DFT calculations further reveal that the high catalytic activity stems from the optimized electronic structure and the charge states of palladium atoms in the defect-containing indium oxide. Our findings provide an effective approach to engineering single atom catalysts at the atomic level and open the door to a wide variety of catalytic reactions.
查看更多>>摘要：The rational integration of multiple functional units into heterogeneous materials to improve catalytic performance is highly desirable for CO2 value-added processes. Herein, a catalyst composed of porous carbon matrix with atomically dispersed Lewis acid sites (i.e., AIO5 motifs) and imidazolium-based poly(ionic liquid)s (denoted as PILs@Al-O-C) was fabricated. Compared with pure Al-O-C or PILs, the optimized PILs@Al-O-C exhibits superior catalytic performance (>90% yield) towards cycloaddition reaction of CO2 and epoxides in the absence of solvent and co-catalyst. The enhanced activity of PILs@Al-O-C is attributed to the synergistic effect among the uniform N sites (Lewis base sites) and abundant bromide anions (nucleophilic agents) in the PILs network, as well as the atomically dispersed Al sites (Lewis acid sites) in the Al-O-C matrix. This work provides an advanced PILs@Al-O-C catalyst for constructing a neat catalytic system towards CO2 fixation.
查看更多>>摘要：Nitrogen coordinated Fe single atoms (Fe-Nx SAs) anchored in carbon support is one of the most efficient electrocatalysts for oxygen reduction reaction (ORR). Engineering the microenvironment of Fe-Nx sites to achieve enhanced activity is still challenging. Herein, we theoretically demonstrate that nitrogen dopants in carbon skeletons can optimize the adsorption of ORR intermediates on Fe-N4 sites. Then, we introduce a rational strategy to anchor Fe-N4 sites in nitrogen-rich carbon support with abundant tubular channels (Fe-SAs@NCTCs). Fe-SAs@NCTCs exhibits encouraging ORR performance with a half-wave potential of 0.91 V in 0.1 M KOH and 0.80 V in 0.1 M HClO4. The assembled rechargeable Zn-air battery presents high power density and operates steadily with a narrow voltage gap of 0.76 V for 650 h. The results verify that the outstanding ORR activity can be attributed to the abundant nitrogen dopant, hierarchical porous structure, and abundant tubular channels.
查看更多>>摘要：The water-gas shift reaction (WGSR) is an important industrial process for H2 production. Here, we rationally construct alumina supported dual-site copper catalysts, i.e. Cu~+ single atoms (Cu1~+) surrounding Cu nanoparticles (Cu_(NP)~0), for WGSR. Our findings show that CO is tightly adsorbed on surface-enriched Cu1~+ sites to inhibit competitive adsorption with H2O on Cu_(NP)~0 sites. The number of adsorbed CO is two orders of magnitude higher than that on conventional Cu-based catalysts. It significantly increases surface CO concentration, and forms a unique structure of Cu_(NP)~0 "islands" immerged in CO "pool". Benefiting from synergy of Cu1~+ and Cu_(NP)~0 sites, the catalyst with 12% Cu loading exhibits extraordinary and robust catalytic activity, compared to benchmark Cu-Zn-Al catalyst, especially at low temperatures, e.g. 200 °C. The catalyst design strategy and facile synthesis methodology employed in this work could be potentially applied in other related industrial reactions.
查看更多>>摘要：It is highly desirable but challenging to accelerate the dissociative adsorption of CO and lower the energy barriers of C-C coupling in the Fischer-Tropsch synthesis (FTS), both of which are prerequisite for high productivities of long-chain hydrocarbons. Herein, we report the fabrication of N-doped carbon nanotubes assembled hollow polyhedrons with embedded hollow Co (H-Co) nanoparticles (NPs) (H-Co@NCNHP) for highly efficient FTS. H-Co@NCNHP affords an extremely high C_(5+) space time yield of 1.67 × 10~(-5) mol g_(cat)~(-1) s~(-1), outperforming most of Co-based catalysts reported to date. Theoretical calculations demonstrate that, as compared with solid Co NPs with symmetric arrangement of d-orbital electrons, H-Co NPs induce the electron rearrangement of d orbitals (especially d_(z2)) toward the Fermi level, promoting the d-2π* /p coupling between Co active sites and adsorbed CO/intermediates.
查看更多>>摘要：Cadmium sulfide (CdS) has been extensively employed to achieve highly efficient H2 production under visible-light irradiation due to its features of narrow bandgap and appropriate conduction band position. However, fast carriers recombination and severe photocorrosion inevitably result in low carriers utilization, leading to undesirable photocatalytic performance and poor durability. To address the issues, N heteroatoms were introduced into the lattice of hexagonal CdS NPs to prepare the N-doped CdS (N-CdS) nanocatalyst via a wet chemical precipitation coupled with a hydrothermal process. Due to the synergetic promotion of heteroatom-semiconductor coordination (HSC) interaction to body carriers migration of CdS, their recombination behavior was effectively hampered, resulting obviously increased photocurrent density (～2 times) and significantly improved photoexcited carriers utilization. Thereby, high apparent quantum yield (AQY = 32.41%, X = 500 nm) was achieved by the optimized N_(0.2)-CdS nanocatalyst. Under simulated sunlight (SSL) irradiation, about 3983.4 μmol - h~(-1) · g~(-1) of HER rate with excellent photo stability was achieved at absence of cocatalyst, which raises to about 9-fold greater than that of bare CdS NPs. Moreover, density functional theory (DFT) calculations proved that the energy barrier of water splitting on Cd sites and |△G_(H*)| of H2 generation on S sites were reduced obviously due to the synergetic HSC interaction, which thermodynamically accelerated the H2 generation. This study provides a simple and green strategy for gaining highly stable CdS photocatalyst with improved HER photoactivity.
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