title: Ni- and Mn-Promoted Mesoporous Co3O4: A Stable Bifunctional Catalyst with Surface-Structure-Dependent Activity for Oxygen Reduction Reaction and Oxygen Evolution Reaction.
abstract: Efficient bifunctional catalysts for electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are highly desirable due to their wide applications in fuel cells and rechargeable metal air batteries. However, the development of nonprecious metal catalysts with comparable activities to noble metals is still challenging. Here we report a one-step wet-chemical synthesis of Ni-/Mn-promoted mesoporous cobalt oxides through an inverse micelle process. Various characterization techniques including powder X-ray diffraction (PXRD), N2 sorption, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) confirm the successful incorporation of Ni and Mn leading to the formation of Co-Ni(Mn)-O solid solutions with retained mesoporosity. Among these catalysts, cobalt oxide with 5% Ni doping demonstrates promising activities for both ORR and OER, with an overpotential of 399 mV for ORR (at -3 mA/cm(2)) and 381 mV (at 10 mA/cm(2)) for OER. Furthermore, it shows better durability than precious metals featuring little activity decay throughout 24 h continuous operation. Analyses of cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS), Raman, and O2-temperature-programmed desorption (O2-TPD) reveal that redox activity of Co(3+) to Co(4+) is crucial for OER performance, while the population of surface oxygen vacancies and surface area determine ORR activities. The comprehensive investigation of the intrinsic active sites for ORR and OER by correlating different physicochemical properties to the electrochemical activities is believed to provide important insight toward the rational design of high-performance electrocatalysts for ORR and OER reactions.
authors.affiliation: Department of Chemistry, University of Connecticut , U-3060, 55 North Eagleville Road, Storrs, Connecticut 06269, United States.
authors.forename: Wenqiao
authors.initials: W
authors.lastname: Song
authors.affiliation: Department of Materials Science and Engineering & Institute of Materials Science, University of Connecticut , U-3136, 97 North Eagleville Road, Storrs, Connecticut 06269, United States.
authors.forename: Zheng
authors.initials: Z
authors.lastname: Ren
authors.affiliation: Department of Chemistry, University of Connecticut , U-3060, 55 North Eagleville Road, Storrs, Connecticut 06269, United States.
authors.forename: Sheng-Yu
authors.initials: SY
authors.lastname: Chen
authors.affiliation: Department of Chemistry, University of Connecticut , U-3060, 55 North Eagleville Road, Storrs, Connecticut 06269, United States.
authors.forename: Yongtao
authors.initials: Y
authors.lastname: Meng
authors.affiliation: Department of Chemistry, University of Connecticut , U-3060, 55 North Eagleville Road, Storrs, Connecticut 06269, United States.
authors.forename: Sourav
authors.initials: S
authors.lastname: Biswas
authors.affiliation: Corporate Strategic Research, ExxonMobil Research and Engineering , 1545 US Highway 22 East, Annandale, New Jersey 08807, United States.
authors.forename: Partha
authors.initials: P
authors.lastname: Nandi
authors.affiliation: Corporate Strategic Research, ExxonMobil Research and Engineering , 1545 US Highway 22 East, Annandale, New Jersey 08807, United States.
authors.forename: Heather A
authors.initials: HA
authors.lastname: Elsen
authors.affiliation: Department of Materials Science and Engineering & Institute of Materials Science, University of Connecticut , U-3136, 97 North Eagleville Road, Storrs, Connecticut 06269, United States.
authors.forename: Pu-Xian
authors.initials: PX
authors.lastname: Gao
authors.affiliation: Department of Chemistry, University of Connecticut , U-3060, 55 North Eagleville Road, Storrs, Connecticut 06269, United States.|Department of Materials Science and Engineering & Institute of Materials Science, University of Connecticut , U-3136, 97 North Eagleville Road, Storrs, Connecticut 06269, United States.
authors.forename: Steven L
authors.initials: SL
authors.lastname: Suib
keywords: cobalt oxide; mesoporous; oxygen evolution reaction; oxygen reduction reaction; surface structure