AB INITIO STUDY ON ACTIVITY OF EDGE-SITE NI/N/C CATALYST FOR CO2 ELECTROCHEMICAL REDUCTION REACTION WITH EFFECT OF BORON DOPANT ADDITION

• Main Author: Luthfi Maulana, Arifin
• Format: Theses
• Language: Indonesia
• Subjects: Teknik tertentu, alat, perlengkapan, materi
• Online Access: https://digilib.itb.ac.id/gdl/view/56269
• Institution: Institut Teknologi Bandung

Electrochemical reduction of CO2 is a profitable mean in reducing the atmospheric greenhouse gas emission and simultaneously producing valuable chemicals of higher value than CO2 itself. One challenge in designing the electrocatalytic system is to engineer a selective catalyst with low overpotential requirement. Ni-based single atom catalyst demonstrates an exceptional performance; however, its active site-related nature is not yet fully understood and overpotential issues are not uncommon to find. In this research, the thermodynamic stability and CO2 electroreduction activity trend of active sites located in the zigzag- and armchair-edge of graphene support are evaluated using ab initio study. In an attempt to reduce the overpotential, BN dopant is introduced to the Ni-based single atom catalyst structure. The result of formation energy analysis shows that site with NiN4 motif located in the edge-most position of graphene edge is more stable than that positioned in the interior side. BN dopant substitution adjacent to the NiN4 site could decrease the total energy of the system and also the energy barrier of CO2 electrochemical reduction actively (HCOOH pathway) or passively (CO pathway). The presence of BN dopant also generally alters the product selectivity from CO to HCOOH. Zigzag- and armchair-edge sites show the tendency to be CO- and HCOOH-selective, respectively; however, the competing hydrogen evolution reaction obscures this potential. The energetic analysis result is also corroborated with microkinetic simulation via normalized current density analysis. In order to supress the competing hydrogen evolution reaction, looking for the best metal center and dopant pair is not sufficient since the hydrogen adsorption generally occurs on top of a neighboring C atom adjacent to the NiN4 center.