Optimization of Electron Transport Pathway: A Novel Strategy to Solve the Photocorrosion of Ag-Based Photocatalysts.

Although Ag-containing photocatalysts exhibit excellent photocatalytic ability, they present great challenges owing to their photocorrosion and ease of reduction. Herein, an electron acceptor platform of Ag2O/La(OH)3/polyacrylonitrile (PAN) fiber was constructed using a heterojunction strategy and electrospinning technology to develop a novel photocatalytic membrane with a redesigned electron transport pathway. Computational and experimental results demonstrate that the optimized electron transport pathway included intercrystal electron transfer induced by the La-O bond between Ag2O and La(OH)3 as well as electron transfer between the catalyst crystal and electrophilic PAN membrane interface. In addition, the photocatalytic performance of the Ag2O/La(OH)3 membrane for tetracycline (TC) removal was still above 97% after five photocatalytic reaction cycles. Furthermore, the carrier life was greatly extended. Mechanistic study revealed that photogenerated holes on the Ag2O/La(OH)3 membrane were the main reactive species in TC degradation. Overall, this study proposes a novel electron transport pathway strategy that effectively solves the problems of photocatalyst photocorrosion and structural instability.

N,S-Doped Porous Carbon Nanobelts Embedded with MoS2 Nanosheets as a Self-Standing Host for Dendrite-Free Li Metal Anodes.

Metallic Li is one of the most promising anodes for high-energy secondary batteries. However, the enormous volume changes and severe dendrite formation during the Li plating/stripping process hinder the practical application of Li metal anodes (LMAs). We have developed a sulfate-assisted strategy to synthesize a self-standing host composed of N,S-doped porous carbon nanobelts embedded with MoS2 nanosheets (MoS2 @NSPCB) for use in LMAs. In situ measurements and theoretical calculations reveal that the uniformly distributed MoS2 derivatives within the carbon nanobelts serve as stable lithiophilic sites which effectively homogenize Li nucleation and suppress dendrite formation. In addition, the hierarchical porosity and 3D nanobelt networks ensure fast Li-ion diffusion and accommodate the volume change of Li deposits during the plating/stripping process. As a result, a Li-Li symmetric cell using the MoS2 @NSPCB host operates steadily over 1500 h with an ultralow voltage hysteresis (≈24.2 mV) at 3 mA cm-2 /3 mAh cm-2 . When paired with a LiFePO4 cathode, the current collector-free LMA endows the full cell with a high energy density of 460 Wh kg-1 and good cycling performance (with a capacity retention of ≈70% even after 1600 cycles at 10 C).

High Sulfur-doped hollow carbon sphere with multicavity for high-performance Potassium-ion hybrid capacitors.

S doping is an effective strategy to improve the potassium-ion storage performance of carbon-based materials. However, due to the large atomic radius of S and poor thermal stability, it is challenging to synthesize carbon materials with high sulfur content by solid-phase transformation. In this work, we designed a multi-cavity structure that can confine the molten S during heat treatment and make it fully react, then achieving high S doping (7.6 at. %). As we known, S doping can also effectively increase the active sites of carbon materials to obtain higher capacity. In addition, through different ex/in-situ characterizations and DFT calculations, we confirmed that the S atoms can effectively expand the interlayer spacing of carbon, which facilitates the intercalation/deintercalation reaction of K+, thereby significantly improving the rate performance. Therefore, benefiting from the effect of S-doping, the sample exhibits high reversible specific capacity (401.0 mAh g-1 at 0.1 A/g) and rate performance (167.2 mAh g-1 at 5 A/g). The as-assembled K+ hybrid capacitor delivers both high energy density and power density (138.5 W h kg-1 and 7692.5 W kg-1, respectively). This work provides a new approach to design S content carbon-based materials for high performance K+ storage.

B, N stabilization effect on multicavity carbon microspheres for boosting durable and fast potassium-ion storage.

Heteroatom-rich carbon materials deliver superior potassium storage capacity owing to the abundant active sites, but their stability and conductivity are damaged because of the numerous defects and distortion of π-conjugated system. In this work, we amended the adverse influences of heteroatoms on carbon materials through the B, N stabilization effect. Due to an amending effect of B atoms on the N-doped carbon matrix, the integrity of the carbon skeleton and stability of the system are significantly enhanced, and the undesirable defects are transformed into favorable active sites, resulting in the simultaneous improvement of K+ storage capacity, rate performance and cyclic stability. The stabilized materials have a highly reversible carbon structure and fast K+ transfer kinetics, leading to high reversible capacity (300 mA h g-1 at 0.1 A g-1), good rate performance (107.2 mA h g-1 at 10 A g-1) and superior cyclic stability (75.3 % capacity retention from cycle 11 to 2000 at 1 A g-1). Consequently, the constructed devices perform excellent energy densities of 158.8 and 40.7 Wh kg-1 under power densities of 100 and 11250 W kg-1, respectively. This work proposes an effective strategy for significantly improving heteroatom-rich carbon materials, which broadens its application fields in high-performance potassium ion storage.

Conductive bimetal organic framework nanorods decorated with highly dispersed Co3O4nanoparticles as bi-functional electrocatalyst.

The poor electronic conductivity and low intrinsic electrocatalytic activity of metal organic frameworks (MOFs) greatly limit their direct application in electrocatalytic reactions. Herein, we report a conductive two-dimensionalπ-dconjugated Ni and Co bimetal organic framework (MOF)-NiCo-(2,3,6,7,10,11-hexaiminotriphenylene) (NiCo-HITP) nanorods decorated with highly dispersed Co3O4nanoparticles (NPs) as a promising bi-functional electrocatalyst towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) through an effective and facile strategy by modifying the rod-shaped -Ni3HITP2crystals using cobalt ions. The triggered electrocatalytic activity of the resulting MOF-based materials was achieved by increasing the electrical conductivity (7.23 S cm-1) originated from Ni3HITP2substrate and also by creating the cooperative catalysis sites of Co-Nxand Co3O4NPs. Optimized syntheses show a promising ORR activity with a high half-wave potential (0.77 V) and also a significantly improved OER activity compared with pure Ni3HITP2in alkaline electrolyte. Furthermore, a rechargeable Zn-air battery using the as-prepared material as air-cathode also shows a high power density (143.1 mW cm-2)-even comparable to a commercial Pt/C-RuO2-based battery. This methodology offers a new prospect in the design and synthesis of non-carbonized MOF bi-functional electrocatalysts for efficient catalysis towards ORR and OER.