1. Experimental design of the electrocatalytic CO2 reduction of single-atom electrocatalysts based on the first-principle calculation.
- Author
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WANG Zhaojie, CAO Shoufu, LIU Siyuan, LI Jiao, and HU Yuying
- Subjects
SCIENTIFIC literacy ,CATALYST structure ,EXPERIMENTAL design ,CATALYTIC activity ,CARBON offsetting ,ELECTROCATALYSTS ,GEOLOGICAL carbon sequestration ,OXYGEN reduction - Abstract
[Objective] The problems of excessive CO
2 emission, the greenhouse effect, and energy shortage have been widely discussed among countries worldwide. Electrocatalytic CO2 reduction reaction (ECO2 RR) can realize the conversion of CO2 into value-added chemical fuel under mild conditions and the storage of renewable electricity, which is an effective way to promote China's aim of carbon peak and carbon neutrality. To pursue higher catalytic activity and product selectivity, researchers are committed to developing highly efficient ECO2 RR electrocatalysts. In this paper, we designed Mo2 CO2 MXene-based single-atom catalysts (SACs) (TM@Mo2 CO2 -Ov, TM = Fe, Co, Ni) according to the needs of ECO2 RR, focusing on their electronic structure, catalytic performance, as well as reaction mechanism through theoretical simulation of the electrocatalytic process. [Methods] In this work, the CIF file of the Mo2 CO2 MXene structure downloaded from the crystal structure database was first imported into the Materials Studio software. Then, the (110) crystal plane was cleaved, and a vacuum layer of 15 A was created. Afterward, a 3 x 3 supercell treatment was applied to the system. Next, the VASP software was utilized to perform structure optimization. After the Mo2 CO2 structure was optimized, a vacancy site for an oxygen atom on the surface was constructed. Subsequently, the Fe, Co, and Ni metal atoms were introduced into the respective vacancy sites to create the Fe@Mo2 CO2 -Ov, Co@Mo2 CO2 -Ov, and Ni@Mo2 CO2 -Ov catalyst models, respectively. Finally, the VASP software was employed to optimize the catalyst structures and the adsorption structures of the reaction intermediates. The performance evaluation of ECO2 RR on different SACs was obtained by studying the reaction mechanism of the production of C products (CO, HCOOH, CH3 OH, and CH4 ). The free energy of ECO2 RR was calculated using the computational hydrogen electrode mode, wherein the energy of (H+ + e- ) remained equivalent to that of 1/2H2 at normal pressure and temperature. [Results] The calculated results showed the following: 1) In the Mo2 CO2 -Ov framework, single Fe, Co, and Ni atoms replaced the Mo atom at the center of the O defect. After structural optimization, it was found that these three structures did not change significantly, and the bond lengths only changed slightly. 2) The CO2 molecule was stably adsorbed on Fe@Mo2 CO2 -Ov, Co@Mo2 CO2 -Ov, and Ni@Mo2 CO2 -Ov via chemisorption. The structures of CO2 were significantly bent after adsorption, and the calculated absolute values of the interaction exceeded four. The DOS analysis showed that the occupation of d orbitals of Ni, Co, and Fe led to the adsorption difference. The d orbitals of Co and Fe were hybridized with the ng and nM* orbitals of CO2 , which promoted the adsorption and activation of CO2 . 3) The ECO2 RR free energy diagram and reaction path analysis showed that Co@Mo2 CO2 -Ov had higher ECO2 RR activity and better CH4 selectivity and was a better electrocatalyst for the formation of C1 products from ECO2 RR than Fe@Mo2 CO2 -Ov and Ni@Mo2 CO2 -Ov. [Conclusions] By integrating the geometrical analysis, DOS calculation, and free energy analysis, Co@Mo2 CO2 -Ov was established as the ideal ECO2 RR catalyst. The work can achieve the expected goal of significantly enhancing the ECO2 RR performance and improving students' scientific research literacy to explore micromechanisms and processes through the extension of the experimental process. [ABSTRACT FROM AUTHOR]- Published
- 2024
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