Synergy of staggered stacking confinement and microporous defect fixation for high‐density atomic Fe^(Ⅱ)‐N_(4)oxygen reduction active sites

The development of high‐performance nonprecious metal catalysts(NPMCs)to supersede Pt‐based catalysts for the oxygen reduction reaction(ORR)in polymer electrolyte membrane fuel cells is highly desirable but remains challenging.In this paper,we present a pyrolysis strategy for spatial confinement and active‐site fixation using iron phthalocyanine(FePc),phthalocyanine(Pc)and Zn salts as precursors.In the obtained carbon‐based NPMC with a hierarchically porous nanostructure of thin‐layered carbon nanosheets,nearly 100%of the total Fe species are Fe^(Ⅱ)‐N_(4) active sites.In contrast,pyrolyzing FePc alone forms Fe‐based nanoparticles embedded in amorphous carbon with only 5.9%Fe^(Ⅱ)‐N_(4) active sites.Both experimental characterization and density functional theory calculations reveal that spatial confinement through the staggeredπ–πstacking of Pc macrocycles effectively prevents the demetallation of Fe atoms and the formation of Fe‐based nanoparticles via aggregation.Furthermore,Zn‐induced microporous defects allow the fixation of Fe^(Ⅱ)‐N_(4) active sites.The synergistic effect of staggered stacking confinement and microporous defect fixation results in a high density of atomic Fe^(Ⅱ)‐N_(4) active sites that can enhance the ORR.The optimal Fe^(Ⅱ)‐N_(4)‐C electro‐catalyst outperforms a commercial Pt/C catalyst in terms of half‐wave potential,methanol toler‐ance,and long‐term stability in alkaline media.This modulation strategy can greatly advance efforts to develop high‐performance NPMCs.

Synthetic strategy of biomimetic sea urchin-like Co-NC@PANI modified MXene-based magnetic aerogels with enhanced electromagnetic wave absorption properties

The rational and effective combination of multicomponent materials and ingenious microstructure design for efficient electromagnetic wave(EMW)absorption are still challenging.In this paper,MXene was used as the aerogel matrix,modified with sea urchin-like magnetic Co/N-doped carbon@polyaniline(Co-NC@PANI),gelatin was introduced as the reinforcement phase of the aerogel backbone,and a microwave absorber with high efficiency and excellent performance was successfully prepared.The sea urchin-like Co-NC@PANI not only adjusted the impedance matching of the MXene but also introduced a magnetic loss mode into the composite.The multicomponent interfacial polarization,heterostructure,three-dimensional(3D)lightweight porous structure,and electromagnetic synergy strategy enabled the MXene-based aerogel modified by Co-NC@PANI(MCoP)to exhibit surprising EMW absorption properties.The maximum reflection loss(RL_(max))of the aerogel composite reached-62.4 dB,and the effective absorption bandwidth(EAB)reached 6.56 GHz when the loading was only 12%.In addition,through electromagnetic simulation experiments,the change in the electromagnetic field before and after EMW passed through the materials and the distribution of the volume loss density of EMW by the coaxial ring were observed.The coordinated electromagnetic balance strategy in the 3D network provides inspiration for the construction of materials and expands the research direction of lightweight and outstanding microwave absorbers.

Initiative and Visions:Synergy between Development Strategies of China and the Arab States

The economic development of Arab states faces long-time impediments,including the paradox between security and development,de-industrialisation,and market fragmentation.Reflecting on the above-mentioned problems,the Arab states have put forward development strategies for themselves in the first two decades of the 21st century.There are different focuses in the three categories of these strategies,namely labour-intensive industrialisation and urbanisation plans adopted typically by Egypt,Morocco,and Tunisia,economic diversification plans adopted mainly by the Gulf Cooperation Council(GCC)countries,as well as post-conflict reconstruction and development plans of Iraq and Syria.This paper argues that,in terms of trade and investment,capacity relocation and technology transfer,as well as infrastructure construction and market integration,these development plans have considerable potential to be strategically synergized with China’s Belt and Road Initiative,and the various featured paths of synergy of development strategies(SDS)have emerged accordingly.To better implement the Sino-Arab SDS,both sides have created various major“interfaces,”including multilateral and bilateral governmental dialogue mechanisms,the participation of China’s state-owned enterprises in the landmark projects of Arab states,and the market-oriented cooperation between their private sectors.