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Identifying the Origin of Ti 3+ Activity toward Enhanced Electrocatalytic N 2 Reduction over TiO 2 Nanoparticles Modulated by Mixed‐Valent Copper
Author(s) -
Wu Tongwei,
Zhao Haitao,
Zhu Xiaojuan,
Xing Zhe,
Liu Qian,
Liu Tong,
Gao Shuyan,
Lu Siyu,
Chen Guang,
Asiri Abdullah M.,
Zhang Yanning,
Sun Xuping
Publication year - 2020
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.202000299
Subject(s) - electrocatalyst , materials science , dopant , reversible hydrogen electrode , redox , electrochemistry , density functional theory , vacancy defect , copper , adsorption , water splitting , catalysis , inorganic chemistry , electrode , crystallography , chemistry , doping , computational chemistry , photocatalysis , metallurgy , working electrode , optoelectronics , biochemistry
The ambient electrocatalytic N 2 reduction reaction (NRR) enabled by TiO 2 has attracted extensive recent attention. Previous studies suggest the formation of Ti 3+ in TiO 2 can significantly improve the NRR activity, but it still remains unclear what kinds of Ti 3+ are effective. Herein, it is demonstrated that mixed‐valent Cu acts as an effective dopant to modulate the oxygen vacancy (V O ) concentration and Ti 3+ formation, which markedly improves the electrocatalytic NRR performance. In 0.5 m LiClO 4 , this electrocatalyst attains a high Faradic efficiency of 21.99% and a large NH 3 yield of 21.31 µg h −1 mg cat. −1 at –0.55 V vs reversible hydrogen electrode, which even surpasses most reported Ti‐based NRR electrocatalysts. Using density function theory calculations, it is evidenced that mixed‐valent Cu ions modulate the TiO 2 (101) surface with multiple oxygen vacancies, which is beneficial for generating different Ti 3+ 3 d 1 defect states localized below the Fermi energy. N 2 activation and adsorption are effectively strengthened when Ti 3+ 3 d 1 defect states present the splitting of e g and t 2g orbitals, which can be modulated by its coordination structure. The synergistic roles of the three ion pairs formed by the V O defect, including Cu 1+ –Ti 4+ , Ti 3+ –Ti 4+ and Ti 3+ –Ti 3+ , are together responsible for the enhanced NRR performance.