TiO2 photoanodes suffer from low catalytic activity and poor stability under acidic media for water oxidation. Here, we report pH-independent high-efficiency photoelectrochemical (PEC) water oxidation and prolonged stability via simple ionic passivation of rutile TiO2 (rTiO2) surface. The controlled surface passivation by hydroxide ions (OH−) onto the rTiO2 surface (OH-rTiO2) enables extraordinarily high PEC performance and long-term durability independent of the pH value of electrolyte. The OH-rTiO2 photoanode shows a charge transfer efficiency of ∼100% at 1.23 V vs RHE over the entire pH range (pH 0 ∼ pH 14) without incorporation of any co-catalysts, hole scavengers or overlayer, which implies that the molecular surface passivation by hydroxide ions successfully promotes the water oxidation reaction pathway. According to our density functional theory (DFT) calculations, the OH-rTiO2 surface can possess increased hydroxide ion coverage, faster decay of the positive surface charge in acidic environments, and weakened H+ adsorption for pH > 7, which enable enhanced water oxidation performance independent of the pH value of the electrolyte. Thus, our report proves that the ionic passivation by hydroxide ions can affect PEC performances and durability of photoanode materials for pH-universal photoelectrochemical water oxidation.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) ( 2019R1A4A1029237 , 2019R1A2C3010479 , 2019M1A2A2065612 , 2019R1F1A1041822 ). H. C. and S. J. acknowledge the financial support of the Federal Ministry of Education and Research (BMBF) under the “Make Our Planet Great Again – German Research Initiative” (MOPGA-GRI; 57429784) implemented by the German Academic Exchange Service: Deutscher Akademischer Austauschdienst (DAAD). S.S.K. was supported by National Research Foundation of Korea (NRF) Grant funded by the Korean Government (NRF-2019-Global Ph.D. Fellowship Program, 2019H1A2A1076183).
© 2020 Elsevier B.V.
All Science Journal Classification (ASJC) codes
- Environmental Chemistry
- Chemical Engineering(all)
- Industrial and Manufacturing Engineering