Morphology–Property Effect in Electrocatalysis Based on Ni 1-χ Se@Graphene Series with Specific Stoichiometric Ratio

Abstract

© The Author(s) 2015. Due to their special role in surface atoms, charge transfer channels and catalytic active sites, morphologies of electrocatalysts produce morphology-property effects in electrocatalysis. To study this effect, a series of specific stoichiometric ratios of nickel and selenium, Ni1-χSe, with different surface atom concentrations and morphologies, were synthesized on graphene via several thermal-reduction methods. In addition, we systematically investigated the morphology-property effect of a Ni1-χSe series based on electrochemical impedance spectra (EIS), cyclic voltammetry (CV), and Tafel polarization experiments. The Ni1-χSe nanoparticles demonstrated superior performance in electrocatalysis than that of Ni1-χSe nanoplates. After nanoplates were assembled to form nanospheres, Ni1-χSe nanospheres exhibited higher catalytic activity in terms of reducing I3- and multiple times faster charge-transfer velocities than those of Ni1-χSe nanoplates. Synthetically electrocatalytic properties of Ni1-χSe series were also measured as counter cells (CEs) of dye-sensitized solar cells (DSSCs). Ni1-χSe nanoparticles showed a higher power conversion efficiency (PCE) (7.33%) in a DSSC cell than when using a Pt CE (7.02%). The performance of Ni1-χSe nanoplates (6.57%) was worse than that of Ni1-χSe nanoparticles and Pt CEs. Simultaneously the self-assembled Ni1-χSe nanospheres (7.37%) exhibited PCE similar to that found with Ni1-χSe nanoparticles.