title: Scalable Synthesis of Efficient Water Oxidation Catalysts: Insights into the Activity of Flame-Made Manganese Oxide Nanocrystals.
abstract: Chemical energy storage by water splitting is a promising solution for the utilization of renewable energy in numerous currently impracticable needs, such as transportation and high temperature processing. Here, the synthesis of efficient ultra-fine Mn3O4 water oxidation catalysts with tunable specific surface area is demonstrated by a scalable one-step flame-synthesis process. The water oxidation performance of these flame-made structures is compared with pure Mn2O3 and Mn5O8, obtained by post-calcination of as-prepared Mn3O4 (115 m(2)  g(-1)), and commercial iso-structural polymorphs, probing the effect of the manganese oxidation state and synthetic route. The structural properties of the manganese oxide nanoparticles were investigated by XRD, FTIR, high-resolution TEM, and XPS. It is found that these flame-made nanostructures have substantially higher activity, reaching up to 350 % higher surface-specific turnover frequency (0.07 μmolO2  m(-2)  s(-1)) than commercial nanocrystals (0.02 μmolO2  m(-2)  s(-1)), and production of up to 0.33 mmolO2  molMn (-1)  s(-1). Electrochemical characterization confirmed the high water oxidation activity of these catalysts with an initial current density of 10 mA cm(-2) achieved with overpotentials between 0.35 and 0.50 V in 1 m NaOH electrolyte.
authors.affiliation: Nanotechnology Research Laboratory, Research School of Engineering, The Australian National University, Canberra, 2001, Australia.
authors.forename: Guanyu
authors.initials: G
authors.lastname: Liu
authors.affiliation: Research School of Chemistry, The Australian National University, Canberra, 2001, Australia.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Hall
authors.affiliation: Nanotechnology Research Laboratory, Research School of Engineering, The Australian National University, Canberra, 2001, Australia.
authors.forename: Noushin
authors.initials: N
authors.lastname: Nasiri
authors.affiliation: Division of Materials Science and Engineering, Commonwealth Scientific and Industrial Research Organization (CSIRO), Bayview Avenue, Clayton, VIC, 3168, Australia.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gengenbach
authors.affiliation: School of Chemistry, ARC Centre of Excellence for Electromaterials Science, Monash University, Melbourne, 3800, Australia.
authors.forename: Leone
authors.initials: L
authors.lastname: Spiccia
authors.affiliation: Research School of Biology, The Australian National University, Canberra, 2001, Australia.
authors.forename: Mun Hon
authors.initials: MH
authors.lastname: Cheah
authors.affiliation: Nanotechnology Research Laboratory, Research School of Engineering, The Australian National University, Canberra, 2001, Australia. antonio.tricoli@anu.edu.au.
authors.forename: Antonio
authors.initials: A
authors.lastname: Tricoli
mesh_terms: D002384:Catalysis; D060326:Chemistry Techniques, Synthetic; D004563:Electrochemistry; D017895:Manganese Compounds / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D017895:Manganese Compounds; D010087:Oxides; D014867:Water; C027424:manganese oxide
keywords: catalysts; manganese; nanomaterials; oxides; water oxidation