Banca de DEFESA: FELIPE MARINHO FERNANDES

DESCRIPTION OF THE OXYGEN EVOLUTION REACTION ON THE (101) AND (100)

TiO2 SURFACE.

Electrocatalysis, TiO₂, OER, Density Functional Theory.

The oxygen evolution reaction (OER) is the rate-limiting step of water electrolysis and is essential for sustainable hydrogen production. In this work, we investigate the OER on the (101) and (100) surfaces of TiO₂ in the anatase phase, using Density Functional Theory (DFT) calculations to determine thermodynamic and kinetic profiles of the reaction. The analysis of the Gibbs free energies showed that the (100) surface presents a lower thermodynamic overpotential (2.32 V), while the (101) surface exhibits a slightly higher value (2.85 V). However, when considering the activation barriers for the elementary steps of the OER, it was observed that the (101) surface has lower energy barriers, ranging from 0.87 eV to 1.18 eV, while, on the (100) surface, these barriers are significantly higher, reaching up to 2.84 eV. The absence of an activation barrier in the formation of the OOH* intermediate on the (101) surface is one of the factors that favor its greater catalytic efficiency. The scaling relationship between the OOH* and OH* intermediates was analyzed, indicating that the free energy difference between these intermediates remains close to 3.2 eV, which imposes an intrinsic limitation on the catalytic performance. The overestimation of the energy of the O₂* intermediate in the DFT calculations was corrected by adopting an adjustment based on the expected thermodynamic value for the formation of molecular oxygen (4.92 eV), avoiding distortions in the energy profile of the reaction. The results indicate that the isolated evaluation of the thermodynamic overpotential can lead to inaccurate conclusions about the catalytic efficiency, reinforcing the need to also consider the kinetic aspects of the reaction. Thus, the (101) surface of anatase TiO₂ stands out as the most efficient for OER, providing valuable information for the rational design of new catalytic materials aiming at optimizing the energy conversion in electrochemical devices.