First-principles simulation of oxygen evolution reaction (OER) catalytic performance of IrO2 bulk-like structures: Nanosphere, nanowire and nanotube

Abstract

Developing high-efficiency IrO2 catalysts is significant but still challenging in water electrolyzers. Using density functional theory (DFT) calculations, a theoretical study of the OER electrocatalyst was conducted with three types of IrO2 bulk-like surface structures: nanowires, nanospheres and nanotubes. The electron transfer and distribution between adjacent Ir and O atoms were evaluated using Mulliken charge analysis. IrO2 nanowires have strong chemical bond strength with a large average bond population of 0.375 and electron transfer of −0.56/1.109e. Compared with nanospheres, the overpotential of nanowires (0.387 V) is only 63.4% of that of rutile IrO2 bulk. IrO2 nanotubes presented the largest specific-surface area, and its active atom utilization rate was 2–3 times that of nanospheres. By modifying the electronic structure and oxygen adsorption strength of catalysts, the one-dimensional bulk-like structure can effectively enhance the electrochemical stability and catalytic activity. IrO2 nanowires showed the best overall performance due to their stable bond structure and outstanding catalytic activity. Although nanotubes with hollow structures exhibited higher potential, the stability was relativity poor due to the low bond population (0.354). This research theoretically analyzes catalytic and electronic performance of IrO2 catalysts from unit cells to bulk-like surface structures and provides guidance for electrocatalyst development.