Ultrafine PtO2 nanoparticles coupled with a Co(OH)F nanowire array for enhanced hydrogen evolutionElectronic supplementary information (ESI) available: Experimental section and supplementary figures. See DOI: 10.1039/c7cc08870a

In this communication, we report the in situ formation of ultrafine PtO 2 nanoparticles coupled with a Co(OH)F nanowire array (PtO 2 -Co(OH)F NA/TM) via a facile hydrothermal treatment. The PtO 2 -Co(OH)F NA/TM possesses interfacial synergy derived from its favorable composition and structure. It can greatly promote water dissociation and optimize the free energy of H* adsorption, indicating high catalytic activity towards the alkaline HER. PtO 2 -Co(OH)F nanoarray exhibits superior alkaline HER activity due to its favorable composition and structure.