MODELING OF THE OXYGEN EVOLUTION REACTION MECHANISM ON NICKEL-MANGANESE PHOSPHATE SURFACE ACTIVE SITES

• Main Author: Ahmad Syaifullah, Dzaki
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/81285
• Institution: Institut Teknologi Bandung

Hydrogen is a promising clean energy source that is expected to replace fossil fuels in the future. Electrolysis is an environmentally friendly method for producing hydrogen. However, the efficiency of electrolysis is currently low. The oxygen evolution reaction (OER), which requires a high overpotential, is the main obstacle in improving electrolysis efficiency. Therefore, it is necessary to develop electrocatalyst with high catalytic activity for the OER. Transition metal phosphate catalysts have been reported to provide good OER performance, but further exploration is still needed. In this study, nickel-manganese phosphate was modeled using the density functional theory (DFT) to analyze its thermodynamic performance as an OER catalyst. Nickel-manganese phosphate was compared with other catalysts, namely nickel phosphate, nickel-cobalt phosphate, iridium dioxide, and platinum. Thermodynamic analysis was performed through the calculation of Gibbs free energy profile using the computational hydrogen electrode (CHE) method. The surface model with Miller index (100) was identified as the most stable among the various facets. Consequently, facet (100) was selected to model the nickel-manganese phosphate (Ni3Mn3(PO4)4) surface. OER can occur at two sites (Mn and Ni metals) on Ni3Mn3(PO4)4 (100) and one site (Ni metal) on Ni3(PO4)2 (100). Ni3Mn3(PO4)4 (100) was found to have an overpotential that was comparable to that of platinum and iridium dioxide, which were used as reference catalysts. At the Ni site, the overpotential obtained was ?= 0.36 V, which is close to the value of platinum (?= 0.33 V). Meanwhile, at the Mn site, the overpotential was found to be approximately ?= 0.51 V, comparable to iridium dioxide (?= 0.51 V). This suggests that Ni3Mn3(PO4)4 (100) has good performance as an OER catalyst. Performance trend analysis was also conducted by employing Sabatier’s principle and d-band theory.