Insight into oxygen reduction activity and pathway on pure titanium using scanning electrochemical microscopy and theoretical calculations

Xin-Ran Li; Xian-Ze Meng; Qin-Hao Zhang; Lian-Kui Wu; Qing-Qing Sun; Hai-Qiang Deng; Shu-Juan Sun; Fa-He Cao

doi:10.1016/j.jcis.2023.03.127

Insight into oxygen reduction activity and pathway on pure titanium using scanning electrochemical microscopy and theoretical calculations

J Colloid Interface Sci. 2023 Aug:643:551-562. doi: 10.1016/j.jcis.2023.03.127. Epub 2023 Mar 22.

Authors

Xin-Ran Li¹, Xian-Ze Meng², Qin-Hao Zhang¹, Lian-Kui Wu¹, Qing-Qing Sun¹, Hai-Qiang Deng³, Shu-Juan Sun⁴, Fa-He Cao⁵

Affiliations

¹ School of Materials, Sun Yat-sen University, Shenzhen 518107, China.
² School of Materials, Sun Yat-sen University, Shenzhen 518107, China. Electronic address: mengxz@mail.sysu.edu.cn.
³ School of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519082, China.
⁴ School of Chemical Engineering, Hebei University of Technology, Tianjin 300130, China.
⁵ School of Materials, Sun Yat-sen University, Shenzhen 518107, China. Electronic address: caofh5@mail.sysu.edu.cn.

PMID: 36990868
DOI: 10.1016/j.jcis.2023.03.127

Abstract

Hypothesis: Unlike noble metals, the oxygen reduction reaction (ORR) behavior on Ti is more complicated due to its spontaneously formed oxide film. This film results in sluggish ORR kinetics and tends to be reduced within ORR potential region, causing the weak and multi-reaction coupled current. Though Ti is being used in chemical and biological fields, its ORR research is still underexplored.

Experiments: We innovatively employed the modified reactive tip generation-substrate collection (RTG/SC) mode of scanning electrochemical microscopy (SECM) with high efficiency of 97.2 % to quantitatively study the effects of film characteristics, solution environment (pH, anion, dissolved oxygen), and applied potential on the ORR activity and selectivity of Ti. Then, density functional theory (DFT) and molecular dynamics (MD) analyses were employed to elucidate its ORR behavior.

Findings: On highly reduced Ti, film properties dominate ORR behavior with promoted 4e^- selectivity. Rapid film regeneration in alkaline/O₂-saturated conditions inhibits ORR activity. Besides, ORR is sensitive to anion species in neutral solutions while showing enhanced 4e^- reduction in alkaline media. All the improved 4e^- selectivities originate from the hydrogen bond/electrostatic stabilization effect, while the decayed ORR activity by Cl^- arises from the suppressed O₂ adsorption. This work provides theoretical support and possible guidance for ORR research on oxide-covered metals.

Keywords: Oxide film; Oxygen reduction reaction; Scanning electrochemical microscopy; Theoretical calculations; Titanium.