Two-Dimensional Covalent Framework Derived Nonprecious Transition Metal Single-Atomic-Site Electrocatalyst toward High-Efficiency Oxygen Reduction.

Designing an active, stable, and nonprecious metal catalyst substitute for Pt in the oxygen reduction reaction (ORR) is highly demanded for energy-efficient and cost-effective prototype devices. Single-atomic-site catalysts (SASCs) have been widely concerning because of their maximum atomic utilization and precise structural regulation. Despite being challenging, the controllable synthesis of SASCs is crucial for optimizing ORR activity. Here, we demonstrate an ultrathin organometallic framework template-assisted pyrolysis strategy to synthesize SASCs with a unique two-dimensional (2D) architecture. Electrochemical measurements revealed that Fe-SASCs displayed an excellent ORR activity in an alkaline media, having a half-wave potential and a diffusion-limited current density comparable to those of commercial Pt/C. Remarkably, the durability and methanol tolerance of Fe-SASCs were even superior to those of Pt/C. Furthermore, Fe-SASCs displayed a maximum power density of 142 mW cm-2 with a current density of 235 mA cm-2 as a cathode catalyst in a zinc-air battery, showing its great potential for practical applications.

A Two-Dimensional van der Waals Heterostructure with Isolated Electron-Deficient Cobalt Sites toward High-Efficiency CO2 Electroreduction.

Electrochemical CO2 conversion is a promising way for sustainable chemical fuel production, yet the conversion efficiency is strongly limited by the sluggish kinetics and complex reaction pathways. Here we report the ultrathin conjugated metalloporphyrin covalent organic framework epitaxially grown on graphene as a two-dimensional van der Waals heterostructure to catalyze CO2 reduction. Operando X-ray absorption and density functional theory calculations reveal the strong interlayer coupling leads to electron-deficient metal centers and speeds up electrocatalysis. The Co(III)-N4 centers exhibit a CO Faradaic efficiency of 97% at a partial current density of 8.2 mA cm-2 in an H-cell, along with a stable running over 30 h. The selectivity of CO approached 99% with a partial current density of 191 mA cm-2 in a liquid flow cell, and the turnover frequency achieved 50 400 h-1 at -1.15 V vs RHE, outperforming most reported organometallic frameworks. This work highlights the key role of strong electronic coupling between van der Waals layers for accelerating the dynamics of CO2 conversion.

Graphdiyne/Graphene Heterostructure: A Universal 2D Scaffold Anchoring Monodispersed Transition-Metal Phthalocyanines for Selective and Durable CO2 Electroreduction.

Electrochemical CO2 reduction (CO2R) is a sustainable way of producing carbon-neutral fuels, yet the efficiency is limited by its sluggish kinetics and complex reaction pathways. Developing active, selective, and stable CO2R electrocatalysts is challenging and entails intelligent material structure design and tailoring. Here we show a graphdiyne/graphene (GDY/G) heterostructure as a 2D conductive scaffold to anchor monodispersed cobalt phthalocyanine (CoPc) and reduce CO2 with an appreciable activity, selectivity, and durability. Advanced characterizations, e.g., synchrotron-based X-ray absorption spectroscopy (XAS), and density functional theory (DFT) calculation disclose that the strong electronic coupling between GDY and CoPc, together with the high surface area, abundant reactive centers, and electron conductivity provided by graphene, synergistically contribute to this distinguished electrocatalytic performance. Electrochemical measurements revealed a high FECO of 96% at a partial current density of 12 mA cm-2 in a H-cell and an FECO of 97% at 100 mA cm-2 in a liquid flow cell, along with a durability over 24 h. The per-site turnover frequency of CoPc reaches 37 s-1 at -1.0 V vs RHE, outperforming most of the reported phthalocyanine- and porphyrin-based electrocatalysts. The usage of the GDY/G heterostructure as a scaffold can be further extended to other organometallic complexes beyond CoPc. Our findings lend credence to the prospect of the GDY/G hybrid contributing to the design of single-molecule dispersed CO2R catalysts for sustainable energy conversion.

Highly efficient mesoporous polymer supported phosphine-gold(i) complex catalysts for amination of allylic alcohols and intramolecular cyclization reactions.

A series of novel heterogeneous gold(i) catalysts were synthesized by immobilizing gold(i) complexes on ordered mesoporous polymer FDU-15 and characterized by XRD, N2 adsorption-desorption, FT-IR, TEM, EDS, etc. The catalytic activities of these catalysts were evaluated by the amination reactions of allylic alcohols. Among the catalysts investigated, FDU-(p-CF3Ph)2PAuCl (3d) was identified as the most efficient catalyst. Compared to the homogeneous catalyst, the enhanced catalytic activity of the heterogeneous gold(i) catalyst is closely related to the mesoporous structure of FDU-15. The catalytic system was suitable for a broad range of substrates and can be easily recovered and recycled at least twelve times without significant loss of catalytic activity. In addition, the catalytic performance of 3d was further examined for intramolecular cyclization for the synthesis of heterocyclic compounds.

Label-free electrochemical immunoassay of Bcl-2 protein expression on tumor cells.

Bcl-2 protein is one of the anti-apoptotic members in Bcl-2 family proteins. It can regulate apoptosis in response to a wide variety of toxic agents, which has a close relationship with drug-resistance of tumor cells. Electrochemical impedance spectroscopy measurements were employed to quantify the cell concentration and analyze the expression of Bcl-2 protein on tumor cells and drug-resistant tumor cells based on the competitive immunoassay. Bcl-2 antibody and bovine serum albumin were adsorbed on Au nanoparticles to construct nanocomposites that could be captured on the Bcl-2 protein modified electrode. The binding of the nanocomposites resulted in a great increase of the charge-transfer resistance (Rct) due to the strong steric hindrance effect and this effect was inhibited in the presence of MCF-7 cells and MCF-7/ADR cells owing to the competitive immunoreaction between the nanocomposites and Bcl-2 proteins on cells. Under the optimal conditions, the charge-transfer resistance change (ΔRct) is proportional to the logarithm of the cells concentration from 5×10(2) to 1.6×10(6) cell mL(-1) with a detection limit of 170 cell mL(-1). The expression of Bcl-2 protein on MCF-7/ADR cells was found to be significantly higher than that in MCF-7 cells, indicating that the up-regulation of Bcl-2 protein is one of characteristics of drug-resistant tumor cells.