ABSTRACT
Electrocatalytic CO2 reduction to value-added hydrocarbon products using metallic copper (Cu) catalysts is a potentially sustainable approach to facilitate carbon neutrality. However, Cu metal suffers from unavoidable and uncontrollable surface reconstruction during electrocatalysis, which can have either adverse or beneficial effects on its electrocatalytic performance. In a break from the current catalyst design path, we propose a strategy guiding the reconstruction process in a favorable direction to improve the performance. Typically, the controlled surface reconstruction is facilely realized using an electrolyte additive, ethylenediamine tetramethylenephosphonic acid, to substantially promote CO2 electroreduction to CH4 for commercial polycrystalline Cu. As a result, a stable CH4 Faradaic efficiency of 64% with a partial current density of 192 mA cm-2, thus enabling an impressive CO2-to-CH4 conversion rate of 0.25 µmol cm-2 s-1, is achieved in an alkaline flow cell. We believe our study will promote the exploration of electrochemical reconstruction and provide a promising route for the discovery of high-performance electrocatalysts.
ABSTRACT
Objective@#To understand current situation of school meal program in Hebei Province and the satisfaction among students and their parents.@*Methods@#Multi-stage random cluster sampling was used to select 24 primary and secondary schools in the three cities of Shijiazhuang, Tangshan and Cangzhou in Hebei Province. A total of 2 739 students from grades 2, 5 and 8 were randomly selected, and 2 716 parents were surveyed.@*Results@#There were 958 students who were very satisfied with the school lunch, 717 who were more satisfied, 686 who were generally satisfied, 221 who were less satisfied, and 157 who were very dissatisfied. Among them, the satisfaction of students in Shijiazhuang and Tangshan was higher than that in Cangzhou(Z=51.42, P<0.01), and the satisfaction of students in urban areas was higher than that in suburbs(Z=4.12, P<0.01). The satisfaction of young students was higher than that of high students(Z=151.42, P<0.01). There were statistically significant differences in some aspects which as food hygiene, food appearance, lunch quantity, food tastes, foodpairing and lunch price among parents of students in the three cities(P<0.01).@*Conclusion@#Students and parents are generally statisfied with school lunches, but the taste of meals served in schools needs to be improved, and the government needs to invest more in school meals and provide scientific training for cafeteria staff on a regular basis. Parents’ opinions and suggestions on feeding to improve the quality of feeding.
ABSTRACT
Fischer-Tropsch synthesis (FTS) is a promising technology to convert syngas derived from non-petroleum-based resources to valuable chemicals or fuels. Selectively producing target products will bring great economic benefits, but unfortunately it is theoretically limited by Anderson-Schulz-Flory (ASF) law. Herein, we synthesize size-uniformed cobalt nanocrystals embedded into mesoporous SiO2 supports, which is likely the structure of water-melon seeds inside pulps. We successfully tune the selectivity of products from diesel-range hydrocarbons (66.2%) to gasoline-range hydrocarbons (62.4%) by controlling the crystallite sizes of confined cobalt from 7.2 to 11.4 nm, and modify the ASF law. Generally, larger Co crystallites increase carbon-chain growth, producing heavier hydrocarbons. But here, we interestingly observe a reverse phenomenon: the uniformly small-sized cobalt crystallites can strongly adsorb active C* species, and the confined structure will inhibit aggregation of cobalt crystallites and escape of reaction intermediates in FTS, inducing the higher selectivity towards heavier hydrocarbons.
