RESUMEN
The copper-based (Cu-based) electrocatalytic materials effectively carry out the electrocatalytic carbon dioxide reduction reaction (CO2RR) toward C2+ products, yet the superiority and stability of the oxidation state of Cu are still worth studying. Herein, we designed and prepared three Cu-based electrocatalysts with different oxidation states to study the valence state-activity relationship. Among these Cu-based electrocatalysts, the Cu2O nanosheets with thickness of only 0.9 nm show an extremely high C2+ Faraday efficiency (FEC2+) of â¼81%, and the FEC2+ has an increase of 37% compared with the traditional CuOx phase. The ultrathin two-dimensional (2D) nanosheet structure with abundant oxygen vacancies can stabilize the oxidation state of Cu to improve the selectivity for C2+ products in CO2RR. In situ Raman spectroscopy and density functional theory calculations demonstrate that the rich Cu+ in the ultrathin 2D Cu2O nanosheets is the most suitable oxidation state for *CO adsorption and coverage on the catalyst surface, which promotes the C-C coupling reaction in CO2RR. This work provides an excellent catalyst for CO2RR toward C2+ products.
RESUMEN
The conventional production technique employed for low-permeability tight reservoirs exhibits limited productivity. To solve the problem, an acetate-type supercritical carbon dioxide (scCO2) thickener, PVE, which contains a large number of microporous structures, was prepared using the atom transfer radical polymerization (ATRP) method. The product exhibited an ability to decrease the minimum miscibility pressure of scCO2 during a solubility test and demonstrated a favorable extraction efficiency in a low-permeability tight core displacement test. At 15 MPa and 70 °C, PVE-scCO2 at a concentration of 0.2% exhibits effective oil recovery rates of 5.61% for the 0.25 mD core and 2.65% for the 5 mD core. The result demonstrates that the incorporation of the thickener PVE can effectively mitigate gas channeling, further improve oil displacement efficiency, and inflict minimal damage to crude oil. The mechanism of thickening was analyzed through molecular simulation. The calculated trend of thickening exhibited excellent agreement with the experimental measurement rule. The simulation results demonstrate that the contact area between the polymer and CO2 increases in direct proportion to both the number of thickener molecules and the viscosity of the system. The study presents an effective strategy for mitigating gas channeling during scCO2 flooding and has a wide application prospect.