Tailoring electrocatalytic activity of titanate perovskite oxides for enhancing oxygen and hydrogen evolution reactions

Abstract

This thesis focuses on the preparation, characterization, and optimization of Ti-based perovskites for water splitting, particularly for OER. These materials are synthesized primarily via a modified sol-gel method. The development and implementation of a double E strategy resulted in a significant enhancement of the catalytic activity of Ti-based perovskites for water splitting.

A series of La₀.₂₊₂ₓCa₀.₇₋₂ₓTi₁₋ₓCoₓO₃ (LCTCoₓ) perovskites with different Co doping levels are synthesized. Reduced LCTCo₀.₁₁ (R-LCTCo₀.₁₁) is identified as a superior OER catalyst by controlling reduction time and temperature. It exhibits excellent mass activity (based on Co), achieving approximately 1700 mA mg⁻¹ at an overpotential of 450 mV, surpassing the benchmark catalyst RuO₂. The process utilized to enhance the OER catalytic activity of Co-doped Ti-based perovskites is known as redox exsolution.

Although the OER catalytic activity of La₀.₂₅Ca₀.₆₅Ti₀.₉₅Fe₀.₀₅O₃ (LCTFe) can be enhanced through redox exsolution, it is less effective than LCTCo. To further optimize the performance of LCTFe, a unique strategy, the double E strategy, is employed. This strategy combines redox exsolution and electrodeposition, resulting in R-LCTFe/Ni. This innovative approach, a novel contribution of this thesis, has proven effective.

R-LCTFe/Ni demonstrates remarkable OER catalytic activity, achieving overpotentials of only 331 mV at a current density of 10 mA cm⁻². It also exhibits notable HER catalytic activity, making it a bifunctional catalyst for water splitting. Additionally, the successfully synthesized R-LCTFe/Co catalyst also shows exceptional water splitting catalytic activity, providing preliminary evidence of the transferability of the double E strategy.

During the preparation of R-LCTNi/Co, the conditions for electrodeposition are carefully controlled and selected, leading to an optimization of the double E strategy. The resulting R-LCTNi/Co exhibits a low overpotential of 281 mV at a current density of 10 mA cm⁻², outperforming numerous state-of-the-art catalysts. This further substantiates the transferability of the double E strategy.