Adsorption-driven heat pumps (AHPs) based on metal–organic frameworks (MOFs) have been garnering rapidly growing research interests due to their outstanding adsorption performance.
Cu-based materials are promising catalysts for the electrochemical CO 2 reduction reaction (CO 2 RR). However, they frequently have a low Faradaic efficiency (FE) and selectivity for a specific single product. Particularly, the precise construction of a Cu microenvironment is a great challenge in the design and fabrication of excellent Cu-based CO 2 RR catalysts. In order to systematically regulate the Cu metal site environment, the classic HKUST-1 containing paddlewheel Cu coordination nodes was used as a template and modified with the atomic layer infiltration (ALI) technique in this work. A detailed structural analysis shows that a uniform distribution of Zn−O−Zn sites is introduced into HKUST-1 and linked to neighboring Cu nodes without changing the original morphology and structure. In comparison with pristine HKUST-1, the FE for CO increases from 20−30% to 70−80% for the ALI-modified HKUST-1 within the tested overpotential range. Density functional theory (DFT) simulations prove that the modification with Zn−O−Zn by ALI enhances the adsorption enthalpy of CO 2 and strengthens the bonding interaction between the COOH* intermediate and the adsorption center, thereby reducing the whole reaction barrier and accelerating CO formation. The proposed ALI technique elucidates the reliance of CO 2 RR selectivity on the Cu microenvironment and provides a platform for regulating the coordination environments of Cu or other metal-based electrocatalysts to facilitate the high selectivity of CO 2 RR in the future.
This paper describes the structural characteristics of zeolite; studies the factors influencing the defluorining capacity of activated zeolite, such as fluorine concentration, pH value, absorption time of the water examples, and further verifies the technical practicability of the application of activated zeolite in defluorining of drinking water. The results indicated at suitable condition of regeneration the adsorption capacity of zeolite was steady, it can be used repeatedly.
Carbon dioxide (CO2) is the most notorious greenhouse gas, released by both natural and artificial processes. In an ideal scenario, the production and consumption of CO2 should be balanced so that the concentration of CO2 in atmosphere remains constant to maintain environmental stability. Unfortunately, with the intensification of human industrial activities, this balance has gradually been disrupted, leading to more CO2 production and making global warming a pressing issue. With carbon neutrality gaining increasing attention, electrochemical CO2 reduction reaction (CO2RR) has emerged as a research orientation which converts CO2 to value-added products while storing renewable energy. Cu-based electrocatalysts have been studied extensively for the CO2RR into hydrocarbons in aqueous solutions under environmental conditions. However, they frequently endure low Faradaic Efficiency (FE) and selectivity of specific single product. Particularly, precise construction of Cu micro-environment is of great challenge for the design and fabrication of excellent Cu-based CO2RR catalysts.
Atomic layer infiltration (ALI) allows gas phase precursors to penetrate and diffuse into porous substrates through their nanoporous structures and to grow within the subsurface. Aiming at systematically regulating the Cu metal site micro-environment, porous HKUST-1 containing paddle-wheel Cu coordination nodes was chosen as a template and modified with ALI technique in this work. Various metals were introduced into HKUST-1 using ALI method to construct bimetallic sites which tended to produce CO, HCOOH and other products with high FEs. Density Functional Theory (DFT) calculations prove the modification with metals by ALI enhances the adsorption enthalpy of CO2 and alters the bonding interaction between reaction intermediates and adsorption center, thereby changing the reaction pathways. MOF conversion technique based on atomic layer deposition (ALD) will be utilized to fabricate HKUST-1 thin film in our future work, which allows nanometer precision of catalyst loading to balance active-site density with mass/charge transfer. The proposed ALI and ALD techniques elucidate the reliance of CO2RR selectivity on the Cu micro-environment and provide a platform for regulating Cu or other metal-base electrocatalyst coordination environment to facilitate high selectivity of CO2RR in the future
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