Carbon nanotubes can be functionalized by oxidation of HNO 3 or H 2 SO 4 -HNO 3 . The latter shows a higher capability in producing a high density of surface functional groups. These groups can act as specific nucleation sites for a well-dispersed deposition of Pt clusters on the surface of carbon nanotubes. These modified carbon nanotube materials were investigated by TEM, XPS, and DRIFT. A deposition mechanism is tentatively proposed and discussed.

Advanced batteries with long cycle life and capable of harnessing more energies from multiple electrochemical reactions are both fundamentally interesting and practically attractive. Herein, we report a robust hybrid zinc-battery that makes use of transition-metal-based redox reaction (M-O-OH → M-O, M = Ni and Co) and oxygen reduction reaction (ORR) to deliver more electrochemical energies of comparably higher voltage with much longer cycle life. The hybrid battery was constructed using an integrated electrode of NiCoO nanowire arrays grown on carbon-coated nickel foam, coupled with a zinc plate anode in alkaline electrolyte. Benefitted from the M-O/M-O-OH redox reactions and rich ORR active sites in NiCoO, the battery has concurrently exhibited high working voltage (by M-O-OH → M-O) and high energy density (by ORR). The good oxygen evolution reaction (OER) activity of the electrode and the reversible M-O ↔ M-O-OH reactions also enabled smooth recharging of the batteries, leading to excellent cycling stabilities. Impressively, the hybrid batteries maintained highly stable charge-discharge voltage profile under various testing conditions, for example, almost no change was observed over 5000 cycles at a current density of 5 mA cm after some initial stabilization. With merits of higher working voltage, high energy density, and ultralong cycle life, such hybrid batteries promise high potential for practical applications.

In this work, carbon nanotubes were activated with Pd-Sn catalytic nuclei via a singlestep activation approach. These activated nanotubes were used as precursors for obtaining nickel-and palladium-decorated nanotubes via electroless plating. Activation of the nanotube surfaces promoted specific deposition of metal on the catalytic tube surfaces. As a result, carbon nanotubes densely coated with metal nanoparticles were obtained with reduced metal deposition in the reaction solution.