Nitrogen-doped and nitrogen and oxygen codoped carbon nanobelts (CNBs) (denoted as N-CNBs and N-O-CNBs, respectively) are respectively obtained by pyrolyzing the self-aligned polypyrrole (PPy) NBs and Se@poly(2-methoxy-5-nitroaniline) core@shell nanowires. Particularly, the uniform size, unique nanostructure, and well-defined edges of the PPy NBs result in the uniform size of the doped CNBs with an extraordinarily high N doping level (≈16 at%), especially the very large concentrations of the redox active pyridinic (9 at%) and pyrrolic N (3.5 at%) species. Furthermore, the precursors in highly self-aligned, dense arrays give rise to a very high packing density for the N-CNBs and N-O-CNBs. These incomparable features provide not only appropriate pathways for the introduction of pseudocapacitance via rapid Faradaic reactions and enhancement of volumetric capacitance but also structural design and synthesis approach to new types of nanostructured carbon. Notably, the N-CNBs obtained at the pyrolysis temperature of 800 °C (N-CNB8) in symmetric electrochemical cells deliver a specific capacitance of 458 F g and ultrahigh volumetric capacitance of 645 F cm in aqueous solution, which are among the best performance ever reported for carbon-based supercapacitive materials.
The core−shell-structured Co−Z@TiO 2 (N 2 +O 2 ) catalyst, which was prepared by subsequent pyrolysis and calcination from precursor ZIF-67 coated by amorphous TiO 2 , was applied in Fischer− Tropsch synthesis (FTS). Compared with Co−Z@TiO 2 catalyst, which was directly calcinated in air (Co−Z@TiO 2 (O 2 )) or pyrolyzed in N 2 (Co−Z@TiO 2 (N 2 )), the Co−Z@TiO 2 (N 2 +O 2 ) catalyst showed better dispersion, easier reducibility, and optimal metal cobalt particle size (8.4 nm) due to the intermediate pyrolysis treatment and core−shell structure. The Co−Z@TiO 2 (N 2 +O 2 ) catalyst exhibited high cobalt time yield (14.84 μmol CO •g Co −1•s −1 ), high selectivity to C 5+ (81.5%), and low selectivity to low carbon hydrocarbon (CH 4 (12.7%) and C 2 −C 4 (5.8%)). The core−shell structure could enhance diffusion limitations to transform intermediate products into heavier hydrocarbons. After 110 h of evaluation, the Co−Z@TiO 2 (N 2 +O 2 ) catalyst still maintained good catalytic performance and cobalt particle size distribution.
Introduction: Urban resilience construction can aid in the management of urban crises and enhance the quality of the human living environment. Compared to metropolises in developed regions, cities in underdeveloped regions with unsatisfactory natural environments, insufficient economic and social development, and inadequate infrastructure construction are highly vulnerable to challenges posed by natural disasters, epidemics, and climate change. Comprehensive quantitative evaluations are needed to identify avenues for enhancing urban resilience.Methods: This study employs the TOPSIS entropy weight method and coupled coordination model to evaluate the economic, social, environmental, and infrastructure resilience of six cities and states along the Sichuan-Tibet Railway in China from 2015 to 2020. Furthermore, correlation and gray correlation analysis are used to identify the primary factors influencing the urban resilience of underdeveloped regions.Results: Firstly, during 2015-2020, the overall urban resilience of each city and state maintained an increasing trend, with different trends in the evolution of the four resilience indices and differences among cities, and the highest overall resilience is in Lhasa. Secondly, the coupling coordination between the overall resilience and each resilience aspect maintained an increasing trend and differed significantly from each other. Finally, the social and economic resilience of each city and state maintained an increasing trend and differed significantly from each other.Discussion: Economic, social, environmental, and infrastructure factors each have their own characteristics in influencing urban resilience. Based on the results, we present a three-dimensional evaluation model for analyzing the evolutionary trajectories and resilience patterns of cities. This work intends to present new concepts for assessing and optimizing urban resilience in underdeveloped regions using quantitative methodologies, as well as providing references for urban resilience construction in these places.
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