Because of the permission of the manipulations of modular construction on the atomic level, covalent organic frameworks (COFs) have attracted extensive attention in the electrocatalytic field. Owing to the lack of metal sites in pristine COFs constructed only by metal-free organic building units, it generally exhibits extremely low electrocatalytic activity. Thereby, linking metal sites on the backbone of pyrolysis-free COFs but not loading them on the surface to enhance the electrocatalytic activity is highly desirable but still remains a huge challenge. To this end, herein, we report an efficient and general cation-exchange strategy to synthesize Ni/Fe metal-ion-incorporated COFs (Ni x Fe1–x @COF-SO3) for the oxygen evolution reaction (OER) based on the fundamental structure design of COFs. Impressively, the turnover frequency (TOF) value in Ni0.5Fe0.5@COF-SO3 reaches 0.14 s–1 at the overpotential of 300 mV, which outperforms most recently reported OER electrocatalysts, indicative of ultrahigh metal-atom utilization efficiency.
O2/H2O combustion technology, as the next generation of oxy-fuel combustion technology with great potential, can greatly increase the utilization rate of clean energy CH4. In this paper, the natural gas combustion process under 6 operating conditions of O2/H2O atmosphere and O2/FH2O atmosphere is numerically simulated. The horizontal analysis is carried out on the characteristics of H2O fraction, CO2 volume fraction and the amount of pollutants (NOx, carbon black), and in-depth exploration of the content of additive H2O and the influence of chemical action on the above characteristics. The research results show that the chemical effects of H2O have a negative effect on combustion temperature, and the physical effects are dominant. The chemical effects of H2O have a great impact on CO production and little effect on the production of CO when the proportion of H2O is 65-79%. The chemical effects of H2O inhibit the formation of NOx and carbon black when the proportion of H2O is within the range of 55-70%. The chemical effect has the greatest impact on the formation of dyes (NOx, carbon black) when the proportion of H2O is within the range of 65-70%.
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