title: Titanium Dioxide-Grafted Copper Complexes: High-Performance Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Media.
abstract: The sluggish kinetics of the oxygen reduction reaction (ORR) at the cathodes of fuel cells significantly hampers fuel cell performance. Therefore, the development of high-performance, non-precious-metal catalysts as alternatives to noble metal Pt-based ORR electrocatalysts is highly desirable for the large-scale commercialization of fuel cells. TiO2 -grafted copper complexes deposited on multiwalled carbon nanotubes (CNTs) form stable and efficient electrocatalysts for the ORR. The optimized catalyst composite CNTs@TiO2 -ZA-[Cu(phen${{^{{\rm NO}{_{2}}}}}$)(BTC)] shows surprisingly high selectivity for the 4 e(-) reduction of O2 to water (approximately 97 %) in alkaline solution with an onset potential of 0.988 V vs. RHE, and demonstrates superior stability and excellent tolerance for the methanol crossover effect in comparison to a commercial Pt/C catalyst. The copper complexes were grafted onto the surface of TiO2 through coordination of an imidazole-containing ligand, zoledronic acid (ZA), which binds to TiO2 through its bis-phosphoric acid anchoring group. Rational optimization of the copper catalyst's ORR performance was achieved by using an electron-deficient ligand, 5-nitro-1,10-phenanthroline (phen${{^{{\rm NO}{_{2}}}}}$), and bridging benzene-1,3,5-tricarboxylate (BTC). This facile approach to the assembly of copper catalysts on TiO2 with rationally tuned ORR activity will have significant implications for the development of high-performance, non-precious-metal ORR catalysts.
authors.affiliation: Key Laboratory for Advanced Materials of MOE, Department of Chemistry, East China University of Science and Technology, Shanghai, 200237 (China).
authors.forename: Fei-Fei
authors.initials: FF
authors.lastname: Wang
authors.affiliation: Key Laboratory for Advanced Materials of MOE, Department of Chemistry, East China University of Science and Technology, Shanghai, 200237 (China).
authors.forename: Ping-Jie
authors.initials: PJ
authors.lastname: Wei
authors.affiliation: Key Laboratory for Advanced Materials of MOE, Department of Chemistry, East China University of Science and Technology, Shanghai, 200237 (China).
authors.forename: Guo-Qiang
authors.initials: GQ
authors.lastname: Yu
authors.affiliation: Key Laboratory for Advanced Materials of MOE, Department of Chemistry, East China University of Science and Technology, Shanghai, 200237 (China). liujingang@ecust.edu.cn.
authors.forename: Jin-Gang
authors.initials: JG
authors.lastname: Liu
keywords: copper complexes; non-precious metal catalysts; oxygen reduction reaction; titanium dioxide