Carbon-Intercalated 0D/2D Hybrid of Hematite Quantum Dots/Graphitic Carbon Nitride Nanosheets as Superior Catalyst for Advanced Oxidation.

Efficient charge separation and sufficiently exposed active sites are important for light-driving Fenton catalysts. 0D/2D hybrids, especially quantum dots (QDs)/nanosheets (NSs), offer a better opportunity for improving photo-Fenton activity due to their high charge mobility and more catalytic sites, which is highly desirable but remains a great challenge. Herein, a 0D hematite quantum dots/2D ultrathin g-C3 N4 nanosheets hybrid (Fe2 O3 QDs/g-C3 N4 NS) is developed via a facile chemical reaction and subsequent low-temperature calcination. As expected, the specially designed 0D/2D structure shows remarkable catalytic performance toward the removal of p-nitrophenol. By virtue of large surface area, adequate active sites, and strong interfacial coupling, the 0D Fe2 O3 QDs/2D g-C3 N4 nanosheets establish efficient charge transport paths by local in-plane carbon species, expediting the separation and transfer of electron/hole pairs. Simultaneously, highly efficient charge mobility can lead to continuous and fast Fe(III)/Fe(II) conversion, promoting a cooperative effect between the photocatalysis and chemical activation of H2 O2 . The developed carbon-intercalated 0D/2D hybrid provides a new insight in developing heterogeneous catalysis for a large variety of photoelectronic applications, not limited in photo-Fenton catalysis.

Mixed-phase 1T/2H-WS2 nanosheets on N-doped multichannel carbon nanofiber as current collector-integrated electrode for potassium battery anode.

Potassium-ion batteries (PIBs) have attracted enormous attention due to the increasing lithium battery cost, but their development is still in the pre-mature stage due to the limited selection of electrodes. Herein, a free-standing current-collector-integrated electrode, composed of mixed-phase WS2 nanosheets with nitrogen-doped multichannel carbon nanofibers (N-MCNFs) membrane, is reported for high-performance potassium ion batteries anode. Benefiting the unique multichannel carbon nanostructure as a current collector-integrated electrode as well as mixed-phase lamellar structure WS2 for enhanced potassium ion entry, the 1T/2H-WS2/N-MCNFs hybrid current-collector-free anode delivers an outstanding areal capacity of 2.88 mAh cm-2 (corresponding to 411 mAh/g based on the mass of both electrode and current collector) at a current of 0.7 mA cm-2 as well as long-term cycling stability for over 1000 cycles at a high current of 14 mA cm-2, surpassing the current state-of-art PIB anode. It is believed that our findings based on the high energy current collector integrated electrode at high mass loading would boost future research on practical metal ion batteries.

A General Method for Transition Metal Single Atoms Anchored on Honeycomb-Like Nitrogen-Doped Carbon Nanosheets.

Excavating and developing highly efficient and cost-effective nonnoble metal single-atom catalysts for electrocatalytic reactions is of paramount significance but still in its infancy. Herein, reported is a general NaCl template-assisted strategy for rationally designing and preparing a series of isolated transition metal single atoms (Fe/Co/Ni) anchored on honeycomb-like nitrogen-doped carbon matrix (M1 -HNC-T1 -T2 , M = Fe/Co/Ni, T1 = 500 °C, T2 = 850 °C). The resulting M1 -HNC-500-850 with M-N4 active sites exhibits superior capability for oxygen reduction reaction (ORR) with the half-wave potential order of Fe1 -HNC-500-850 > Co1 -HNC-500-850 > Ni1 -HNC-500-850, in which Fe1 -HNC-500-850 shows better performance than commercial Pt/C. Density functional theory calculations reveal a choice strategy that the strong p-d-coupled spatial charge separation results the Fe-N4 effectively merges active electrons for elevating d-band activity in a van-Hove singularity like character. This essentially generalizes an optimal electronic exchange-and-transfer (ExT) capability for boosting sluggish alkaline ORR activity. This work not only presents a universal strategy for preparing single-atom electrocatalyst to accelerate the kinetics of cathodic ORR but also provides an insight into the relationship between the electronic structure and the electrocatalytical activity.

MXene/Si@SiO x@C Layer-by-Layer Superstructure with Autoadjustable Function for Superior Stable Lithium Storage.

Despite its very high capacity (4200 mAh g-1), the widespread application of the silicon anode is still hampered by severe volume changes (up to 300%) during cycling, which results in electrical contact loss and thus dramatic capacity fading with poor cycle life. To address this challenge, 3D advanced Mxene/Si-based superstructures including MXene matrix, silicon, SiO x layer, and nitrogen-doped carbon (MXene/Si@SiO x@C) in a layer-by-layer manner were rationally designed and fabricated for boosting lithium-ion batteries (LIBs). The MXene/Si@SiO x@C anode takes the advantages of high Li+ ion capacity offered by Si, mechanical stability by the synergistic effect of SiO x, MXene, and N-doped carbon coating, and excellent structural stability by forming a strong Ti-N bond among the layers. Such an interesting superstructure boosts the lithium storage performance (390 mAh g-1 with 99.9% Coulombic efficiency and 76.4% capacity retention after 1000 cycles at 10 C) and effectively suppresses electrode swelling only to 12% with no noticeable fracture or pulverization after long-term cycling. Furthermore, a soft package full LIB with MXene/Si@SiO x@C anode and Li[Ni0.6Co0.2Mn0.2]O2 (NCM622) cathode was demonstrated, which delivers a stable capacity of 171 mAh g-1 at 0.2 C, a promising energy density of 485 Wh kg-1 based on positive active material, as well as good cycling stability for 200 cycles even after bending. The present MXene/Si@SiO x@C becomes among the best Si-based anode materials for LIBs.

Synergetic interaction between neighboring platinum and ruthenium monomers boosts CO oxidation.

Sub-nanometer noble metal catalysts, especially single atom (SA), are a new class of catalytic materials for boosting catalysis and possess unique catalytic properties and high atomic utilization efficiency. Exploring the interaction between two neighboring atom monomers has great potential to further improve the performance of SA catalysts and deepen the understanding on the catalytic mechanism of heterogeneous catalysis at the atomic level. Herein, we demonstrate that the synergetic effect between neighboring Pt and Ru monomers supported on N vacancy-rich g-C3N4 promotes the catalytic CO oxidation. The experimental observation and theoretical simulation reveal that the N vacancy in the g-C3N4 structure builds an optimized triangular sub-nanometer cavity for stabilizing the neighboring Pt-Ru monomers by forming Pt-C and Ru-N bonds. The mechanistic studies based on the in situ IR spectrum and theoretical simulation confirm that the neighboring Pt-Ru monomers possess a higher performance for optimizing O2 activation than Ru-Ru/Pt-Pt monomers or isolated Ru/Pt atoms by balancing the energy evolution of reaction steps in the catalytic CO oxidation. The discovery of the synergetic effect between neighboring monomers may create a new path for manipulating the catalytic properties of SA catalysts.