title: Co-axial heterostructures integrating palladium/titanium dioxide with carbon nanotubes for efficient electrocatalytic hydrogen evolution.
abstract: Considering the depletion of fossil-fuel reserves and their negative environmental impact, new energy schemes must point towards alternative ecological processes. Efficient hydrogen evolution from water is one promising route towards a renewable energy economy and sustainable development. Here we show a tridimensional electrocatalytic interface, featuring a hierarchical, co-axial arrangement of a palladium/titanium dioxide layer on functionalized multi-walled carbon nanotubes. The resulting morphology leads to a merging of the conductive nanocarbon core with the active inorganic phase. A mechanistic synergy is envisioned by a cascade of catalytic events promoting water dissociation, hydride formation and hydrogen evolution. The nanohybrid exhibits a performance exceeding that of state-of-the-art electrocatalysts (turnover frequency of 15000 H2per hour at 50 mV overpotential). The Tafel slope of ∼130 mV per decade points to a rate-determining step comprised of water dissociation and formation of hydride. Comparative activities of the isolated components or their physical mixtures demonstrate that the good performance evolves from the synergistic hierarchical structure.
authors.affiliation: Department of Chemistry 'Giacomo Ciamician', University of Bologna and INSTM, via Selmi 2, Bologna 40126, Italy.
authors.forename: Giovanni
authors.identifier: 0000-0002-6223-2072
authors.initials: G
authors.lastname: Valenti
authors.affiliation: Department of Chemistry 'Giacomo Ciamician', University of Bologna and INSTM, via Selmi 2, Bologna 40126, Italy.
authors.forename: Alessandro
authors.identifier: 0000-0003-2397-9242
authors.initials: A
authors.lastname: Boni
authors.affiliation: Department of Chemical and Pharmaceutical Sciences and INSTM, University of Trieste, via L. Giorgieri 1, Trieste 34127, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Melchionna
authors.affiliation: Department of Chemical Engineering and SUNCAT Center for Interface Science and Catalysis, Stanford University, Stanford, California 94305, USA.
authors.forename: Matteo
authors.initials: M
authors.lastname: Cargnello
authors.affiliation: IMEM-CNR Institute, Parco area delle Scienze 37/A, Parma 43124, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Nasi
authors.affiliation: IMEM-CNR Institute, Parco area delle Scienze 37/A, Parma 43124, Italy.
authors.forename: Giovanni
authors.identifier: 0000-0001-6424-9102
authors.initials: G
authors.lastname: Bertoni
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of Pennsylvania, 220 S. 33rd Street, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Gorte
authors.affiliation: Department of Chemistry 'Giacomo Ciamician', University of Bologna and INSTM, via Selmi 2, Bologna 40126, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Marcaccio
authors.affiliation: Department of Chemistry 'Giacomo Ciamician', University of Bologna and INSTM, via Selmi 2, Bologna 40126, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Rapino
authors.affiliation: Department of Chemical Sciences and ITM-CNR, University of Padova, via F. Marzolo 1, Padova 35131, Italy.
authors.forename: Marcella
authors.initials: M
authors.lastname: Bonchio
authors.affiliation: Department of Chemical and Pharmaceutical Sciences and INSTM, University of Trieste, via L. Giorgieri 1, Trieste 34127, Italy.|ICCOM-CNR Trieste Associate Unit, University of Trieste, via L. Giorgieri 1, Trieste 34127, Italy.
authors.forename: Paolo
authors.identifier: 0000-0003-1082-9157
authors.initials: P
authors.lastname: Fornasiero
authors.affiliation: Department of Chemical and Pharmaceutical Sciences and INSTM, University of Trieste, via L. Giorgieri 1, Trieste 34127, Italy.|Nanobiotechnology Laboratory, CIC biomaGUNE, Paseo de Miramón 182, Donostia-San Sebastián 20009, Spain.|Ikerbasque, Basque Foundation for Science, Bilbao 48013, Spain.
authors.forename: Maurizio
authors.identifier: 0000-0002-8869-8612
authors.initials: M
authors.lastname: Prato
authors.affiliation: Department of Chemistry 'Giacomo Ciamician', University of Bologna and INSTM, via Selmi 2, Bologna 40126, Italy.|ICMATE-CNR Bologna Associate Unit, University of Bologna, via Selmi 2, Bologna 40126, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Paolucci