Research Progress

Researchers Developed Linkage Engineering of Covalent Organic Frameworks for the Oxygen Reduction Reaction

A joint team lead by Prof. ZENG Gaofeng and Associate Prof. XU Qing from Shanghai Advanced Research Institute, CAS and Prof. JIANG Zheng from University of Science and Technology of China employed catalytic linkage engineering to modulate the catalytic behaviors and found the catalytic performance is determined solely by the electron states of carbon atoms in the linkages. The research results were published in Angew Chem Int Ed.


  Covalent organic frameworks (COFs) are the ideal templates to create metal-free catalysts because of their well-defined porous structures, predictable sites distribution and tailored environments. Attention has been put on employing different knots or linkers to advance the catalytic performance, however, the important roles of linkages toward catalyzing the oxygen reduction reaction (ORR) have not been investigated, and which linkage is more suitable for ORR is still under investigation.
  Recently, a joint team lead by Prof. ZENG Gaofeng and Associate Prof. XU Qing from Shanghai Advanced Research Institute, CAS and Prof. JIANG Zheng from University of Science and Technology of China employed catalytic linkage engineering to modulate the catalytic behaviors and found the catalytic performance is determined solely by the electron states of carbon atoms in the linkages.
  The research results were published in Angew Chem Int Ed.
  Researchers developed catalytic COFs using different bonds such as imine, amide, azine, and oxazole bonds to link benzene units to catalyze ORR. Among these COFs, the oxazole-linkage in COFs enables to catalyze the ORR with the highest activity, which achieved a half-wave potential of 0.75V and a limited current density of 5.5mA cm -2.
  Theoretical calculations showed that the carbon atoms in oxazole linkages promoted the formation of the OOH* and OH* intermediates, thus advancing the catalytic activity. This work provides guidance in choosing suitable linkages for ORR. 
  Chemical structures of COFs (azine-, imine-, amide-, and oxazole-COF) with different linkages (Image by SARI)
  

2023-06-02 more+

Researchers Constructed Noninterpenetrated Three-dimensional Covalent Organic Framework for Au Ions Capture

A research team led by Prof. ZENG Gaofeng and Associate Prof. XU Qing at the Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences constructed a novel non-interpenetration 3D COF towards Au ions capture by imine bonds in the frameworks. The research results were published in Adv. Funct. Mater. on Apr. 23rd.

Covalent organic frameworks (COFs) can be ideal platform for detecting or extracting metal ions because of the different functional building units and large surface area. However, most of 3D COFs have interpenetration because of the existence of non-covalent interactions between the adjacent nets, which resulting in decreased surface areas and porosizes, and thus limited their applications in catalysis and molecular/gas adsorption.Recently, a research team led by Prof. ZENG Gaofeng and Associate Prof. XU Qing at the Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences constructed a novel non-interpenetration 3D COF towards Au ions capture by imine bonds in the frameworks. The high surface area and abundant cavities due to the non-interpenetration provided the high Au3+ capacity (570.18 mg g-1), selectivity (99.5%) and efficiency (68.3% adsorption of maximum capacity in 5 mins).The research results were published in Adv. Funct. Mater.on Apr. 23rd. The synthesized BMTA-TFPM-COF displayed good crystallinity with dia topology and a high BET surface area of 1924 m2 g-1. Importantly, the open cavities and exposed C=N bonds from non-fold interpenetration contributed to high capacity, selectivity and stability of Au3+ uptake.The experiments showed the mechanism of Au capture. The protonated C=N bonds due to the influence of the HAuCl4 and the protonated nitrogenous groups could adsorb AuCl4 - and reduce Au(III) to Au(I) and Au(0) in acidic solution. Thus, the BMTA-TFPM-COF with abundant exposed C=N bonds could promote the conversion from Au(III) to Au(I) and Au(0) through the protonated C=N bonds, which further verified that the C=N bonds could participate in the reduction of Au(III).
   Mechanism of 3D COFs (Image by SARI)This study gives new insight into the development of 3D COFs for Au3+ capture. 

2023-04-28 more+

Researchers Developed a Novel Graphene/Silicon Catalyst for Highly Selective Photoelectroreduction of Carbon Dioxide to Ethanol

a research team led by Profs. CHEN Wei and WEI Wei from the Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences reported efficient CO2 photoelectroreduction to ethanol (C2H5OH) over graphene/silicon carbide (SiC) catalysts under simulated solar irradiation with ethanol (C2H5OH) selectivity of >99% and a CO2 conversion rate of up to 17.1mmol gcat-1h-1. The results were published in Angew. Chem. Int. Ed.

Using sunlight to produce valuable chemicals and fuels from carbon dioxide (CO2), i.e., artificial photosynthesis (AP) is a promising strategy to achieve solar energy storage as well as a negative carbon cycle.However, the AP is quite complex and involves multiple sequential and parallel steps. What’s more, thermodynamically favorable C1 products can be produced from multiple AP intermediates, making it challenging to selectively produce target chemicals containing C-C bonds. Therefore, selective synthesis of C2 compounds with a high CO2 conversion rate remains challenging for current AP technologies.Motivated by such a challenge, a research team led by Profs. CHEN Wei and WEI Wei from the Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences reported efficient CO2 photoelectroreduction to ethanol (C2H5OH) over graphene/silicon carbide (SiC) catalysts under simulated solar irradiation with ethanol (C2H5OH) selectivity of >99% and a CO2 conversion rate of up to 17.1mmol gcat-1h-1.The results were published in Angew. Chem. Int. Ed.A graphene/silicon carbon (SiC) composite catalyst, which comprises a SiC substrate, interfacial layer (IL), and few-layer graphene overlayer can help to achieve the precise control of active intermediates for C?C coupling. An optimal IL structure allows photogenerated electrons from the SiC substrate to be facilely transferred to the active sites on the graphene overlayer. Reaction intermediates can then be efficiently formed and stabilized owing to their strong adsorption at the active sites and the high electron density of the graphene surface.Experimental results and first principles calculations show that CH3OH formation is largely suppressed in favor of C-C coupling. C2H5OH is therefore exclusively formed with a selectivity of>99% and a CO2 conversion rate of 17.1mmol gcat-1h-1 under simulated solar irradiation with a small bias (-50 mV bias vs. Ag/AgCl) and ambient conditions. Thus, the photoelectrocatalytic performance of the optimal catalyst in producing C2 products from CO2 was at least two orders of magnitude higher than those of the state-of-the-art AP catalysts.This work paves the way toward an advanced AP strategy to efficiently valorize greenhouse CO2.
  Figure1. Schematic diagram a for highly selective photoelectroreduction of carbon dioxide over graphene/silicon carbide composites (image by SARI)
  Figure 2. Synthetic Scheme, Raman spectra and CO2 photoelectrocatalytic performances. (image by SARI)
  

2023-03-20 more+

Researchers Propose an Effective and Reusable Tandem Catalyst for Plastic Waste Conversion

a research group led by Prof. WANG Hui and Associate Prof. LUO Hu at the Shanghai Advanced Research Institute, Chinese Academy of Sciences developed a tandem catalytic reaction to efficiently convert low-density polyethylene (LDPE) into naphtha, where a naphtha yield of 89.5% is obtained with 96.8% selectivity of C5?C9 hydrocarbons at 250 °C, catalyzed by mechanically mixed β zeolite and Pt@S-1 catalysts.The research results were published in Journal of the American Chemical Society recently.


  The rapid growth of plastic waste is an ever-growing environmental and energy challenge. Selectively converting waste plastics to naphtha, a main feedstock for ethylene and the plastic industry, shows high potential to partially replace petroleum-route naphtha and alleviate global net carbon emissions. However, these active metals on supported catalysts with an open microenvironment showed less effect on the generation of intermediates and selectivity of naphtha.
  Motivated by such a challenge, a research group led by Prof. WANG Hui and Associate Prof. LUO Hu at the Shanghai Advanced Research Institute, Chinese Academy of Sciences developed a tandem catalytic reaction to efficiently convert low-density polyethylene (LDPE) into naphtha, where a naphtha yield of 89.5% is obtained with 96.8% selectivity of C5-C9 hydrocarbons at 250 °C, catalyzed by mechanically mixed β zeolite and Pt@S-1 catalysts.
  The research results were published in Journal of the American Chemical Society recently.
  The selectivity of normal alkanes catalyzed by Pt@S-1 and β zeolite reached 34%, about 10-20% higher than that on Pt/S-1, and the alkane products were narrower. The differences between the two catalysts were possibly due to the confinement effect and shape-selectivity of Pt@S-1. Thus, combined density functional theory (DFT) and molecular dynamics simulations were used to reveal the shape-selectivity process, as the diffusion and shipping of olefin intermediates with the right size were boosted within Pt@S-1, which led to narrower-distributed products.
  This catalyst system displayed stability and high performance for most abundant plastic waste like low-/high-density polyethylene and polypropylene at moderate conditions. With life cycle assessment (LCA), this approach showed 15% energy saving and 30% reduced greenhouse gas emissions compared with conventional routes for plastic production.
  This work provides an upgrading strategy for retaining the value of waste plastics more efficiently and serving as a significant step to realize the circular economy.
  DFT and molecular dynamics calculations (image by SARI)
  

2023-01-19 more+

Researchers Propose a Novel Ordered MEA for High-performance PEMWE

a research team led by Prof. YANG Hui at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences reported a novel ordered MEA based on anode with 3D membrane/catalytic layer (CL) interface and gradient tapered arrays, which not only greatly increases the electrochemical active area but also decreases the overpotentials of both mass transport and ohmic polarization.The research results were published in Nano Letters recently.

Proton exchange membrane water electrolysis (PEMWE) is under intensive investigation because of its advantages as high energy efficiency and hydrogen purity compared to the conventional alkaline water electrolysis. However, as the practical application of the PEMWEs usually runs at high current densities ( ≥1-2 A m-2), insufficient catalyst utilization, limited mass transport and high ohmic resistance of the conventional membrane electrode assembly (MEA) restrict the performance of PEMWE.
  Motivated by such a challenge, a research team led by Prof. YANG Hui at Shanghai Advanced Research Institute (SARI) of the Chinese Academy of Sciences reported a novel ordered MEA based on anode with 3D membrane/catalytic layer (CL) interface and gradient tapered arrays, which not only greatly increases the electrochemical active area but also decreases the overpotentials of both mass transport and ohmic polarization.
  The research results were published in Nano Letters recently.  
  An overall design of the MEA based on anode with ordered arrays, gradient CL and 3D membrane/CL interface structure was proposed and confirmed by scanning electron microscopy, energy disperse spectroscopy and X-ray photoelectron spectroscopy.
  Benefiting from the maximized triple-phase interface, rapid mass transport and gradient CL, such an ordered structure not only greatly increases the electrochemical active area by 4.2 times but also decreases the overpotentials of both mass transport and ohmic polarization by 13.9% and 8.7%, respectively.
  This ordered MEA ensures a performance of 1.801 V @ 2 A cm-2 even with Ir loading as low as 0.2 mg cm-2, which is comparable with conventional MEA with Ir loading of 2 mg cm-2. Further, it can operate stably over 300 h under 1 A cm-2.
  The study provides a simple but effective strategy for the overall design of nanostructured MEA for high-performance and stable PEMWE with low Ir loading.
  Structure and performance of the prepared MEA-GTAs-T1 (Image by SARI)
  

2023-01-09 more+

Researchers Design a Novel Copper Gas Penetration Electrode to Efficiently Reduce CO2 to Multicarbon Products

a research team from the Shanghai Advanced Research Institute of the Chinese Academy of Sciences reported a hierarchical micro/nanostructured Cu(100)-rich hollow-fiber gas penetration electrode (GPE), breaking through the bottleneck of low CO2 solubility limit and realizing electrochemical reduction of CO2 to multicarbon products under ampere level current density.

Electrochemical conversion of CO2 into value-added chemical fuels driven by renewable electrical energy has twofold roles in reducing net CO2 emission and in addressing energy consumption.Although considerable progress has been made in CO2 electroreduction, the current density of CO2 to multicarbon products remains a challenge for sustained industrial-scale implementation. Therefore, it is crucial to develop efficient electrodes with high C2+ yield at high current density.Motivated by this challenge, a research team from the Shanghai Advanced Research Institute of the Chinese Academy of Sciences reported a hierarchical micro/nanostructured Cu(100)-rich hollow-fiber gas penetration electrode (GPE), breaking through the bottleneck of low CO2 solubility limit and realizing electrochemical reduction of CO2 to multicarbon products under ampere level current density.The results were published in Energy & Environmental Science on November 2. The Cu GPEs composed only of metallic copper for electrochemical CO2 reduction reaction to C2+ product, reducing CO2 to C2+ product with a faradaic efficiency of 62.8% and a current density of 2.3 A cm-2 in 0.5 M KHCO3 solution at -1.94 V, approximating to or even outperforming state-of-the-art Cu-based catalysts.Electrochemical results show that optimized mass transfer and enhanced three-phase interface reaction synergistically promote CO2 activation and reduction kinetics. Theoretical calculations further suggest that the Cu(100) facet of Cu GPE favors CO adsorption and dimerization, thus enhancing its catalytic activity.This work represents an encouraging headway in the design and development of new electrode configurations to realize CO2 electroreduction to high-value C2+ chemicals with scalable applications.
  Schematic diagram and electrocatalytic performance of efficient CO2 reduction over copper hollow fiber gas penetration electrode (image by SARI)
  

2022-11-08 more+