Periodic DFT Study of Rutile IrO₂: Surface Reactivity and Catechol Adsorption

Abstract

IrO 2 is a key material for photocatalytic applications as water oxidation catalyst. Despite its increasing interest, little is known about its molecular structure and reactivity. In this study, the surface properties of stoichiometric rutile IrO 2 are investigated by means of periodic density functional theory (DFT), including the structural, energetic, electronic properties and chemical reactivity towards catechol, a probe molecule mimicking photocatalytic linkers. Our results show that the (110)-IrO 2 rutile termination is the most stable, and we discuss the role of the number and type of surface sites in the relative stability compared with (100), (001) and (101) terminations. Regarding the reactivity of the surfaces with catechol, our results show that the molecule dissociates and binds in bidentate, chelate and monodentate modes.Interestingly, we find the chelated mode selectively favored over the (001)

Operando XANES from first-principles and its application to iridium oxide

“…In agreement with previous theoretical studies 10,11,18,20,25 , results of our interface-stability analysis suggests that the (110) termination is among the most stable IrO 2 interfaces at moderate-potential conditions, while the (111) termination has the lowest surface energy at large applied potentials. However, our calculations suggest a reconstructed Ir-rich (101) termination to be the minimum-energy interface under open-circuit conditions.…”

Freestanding interconnected nanocluster textiles for efficient oxygen evolution reaction

“…These planes are thermodynamically less stable than the most stable surface plane (110). A presence of low CN atoms in unstable surface planes (CN < 6 of bulk Ir atom) has been theoretically demonstrated, 28 which is consistent with our STEM-HAADF observations. This could be an origin of high TOF, which we discuss further below.…”

“…Notably, although the heat treatment temperature was moderately low (around the Tammann temperature of $414 C, which is a half of the melting point of IrO 2 in the Kelvin scale, where the atoms acquire an sufficient energy to be mobile), cluster coarsening occurred due to greater atom mobility at high temperatures, and the number of edge sites at which the undercoordinated atoms were located decreased. Although a distortion was observed around the edge for the sample annealed at 450 C, no unstable planes were observed, unlike the sample annealed at 300 C. 28 These results suggest that OH is preferentially adsorbed by the undercoordinated Ir atoms. The reason why catalysts which have high OER activity exhibit high OH concentration was not clear previously 1,22,31 (ESI Fig.…”

Towards maximized utilization of iridium for the acidic oxygen evolution reaction

“…Nb2O5, TiO2, Ta2O3, Ta2O5) when combined with IrO2. For Sn-based materials, the similar lattice parameters, the same valency of Ir(IV) and Sn(IV), similar radii, comparable electronegativities, and interfacial energies between IrO2-rutile and SnO2 favour the formation of mixed oxides [49][50][51][52]. In the following paragraphs, we will discuss the accompanying consequences of this dependency for (1) the activities and (2) the durability of the prepared catalysts.…”

“…The reason lies in the incorporation of Ir(IV) species into the tin oxide host lattice at these temperatures. The surface energies of IrO2-rutile are relatively higher compared to SnO2, making a thermodynamically driven growth of atomically smooth and fully formed layers challenging [49][50][51]. This is true for many oxides commonly used as support materials (e.g.…”