Continuous strain tuning of oxygen evolution catalysts with anisotropic thermal expansion

Abstract

Compressive strain, downshifting the d-band center of transition metal oxides, is an effective way to accelerate the sluggish kinetics of oxygen evolution reaction (OER) for water electrolysis. Here, we find that anisotropic thermal expansion can produce compressive strains of the IrO₆ octahedron in Sr₂IrO₄ catalyst, thus downshifting its d-band center. Different from the previous strategies to create constant strains in the crystals, the thermal-triggered compressive strains can be real-timely tuned by varying temperature. As a result of the thermal strain accelerating OER kinetics, the Sr₂IrO₄ exhibits the nonlinear lnj_o - T⁻¹ (j_o, exchange current density; T, absolute temperature) Arrhenius relationship, resulting from the thermally induced low-barrier electron transfer in the presence of thermal compressive strains. Our results verify that the thermal field can be utilized to manipulate the electronic states of Sr₂IrO₄ via thermal compressive strains downshifting the d-band center, significantly accelerating the OER kinetics, beyond the traditional thermal diffusion effects.

Tuning compressive strain is an effective way to accelerate the oxygen evolution reaction kinetics. Here the authors show that anisotropic thermal expansion induces compressive strains on IrO6 octahedron in Sr2IrO4, shifting its d-band center downward and accelerating water oxidation kinetics beyond traditional thermal diffusion effects.