Feila Liu

Ni–Co oxides nanowire arrays grown on ordered TiO2 nanotubes with high performance in supercapacitors

We develop a facile hydrothermal synthesis method to fabricate mesoporous Ni–Co oxides nanowire arrays on ordered TiO2 nanotubes (Ni–Co oxides NWs@TiO2NTs) as a high-capacity pseudocapacitor material. The composite electrode presented the highest specific capacitance of 2353 F g−1 at a charge and discharge current density of 2.5 A g−1 with excellent cycling ability, retaining 95% of the maximum capacitance after 3000 cycles. Even at a high current density of 50 A g−1, the electrode exhibited a specific capacitance of up to 2173 F g−1. In addition, the testing of a (Ni–Co oxides NWs@TiO2NTs)//(Ni–Co oxides NWs@TiO2NTs) symmetric cell yielded a specific capacitance of up to 144 F g−1 at a current density of 4 A g−1. The much improved capacity and cycling stability may be attributed to the superior conductivity and the aligned structure of the Ni–Co oxides NWs and the TiO2NTs substrate, which can improve electron/ion transport and enhance the kinetics of the redox reactions.

DFT studies on the interaction of PtxRuyMz (M = Fe, Ni, Cu, Mo, Sn, x + y + z = 4, x ≥ 1, y ≥ 1) alloy clusters with O2

The reaction mechanism of O2 dissociation on PtxRuyMz (M = Fe, Ni, Cu, Mo, Sn, x + y + z = 4, x ≥ 1, y ≥ 1) alloy catalysts have been investigated with density functional theory calculations in this work. For bare alloy clusters, bimetallic clusters are more stable than the ternary alloy clusters. The geometries of the PtxRuyMz–O2 system, O–O bond stretching frequency and electronic-structure details have been investigated. The energies of O2 adsorption on PtRu clusters are slightly higher than those on PtxRuyMz clusters, and the more charge transfer to O2 from the metal cluster, the higher O2 the adsorption energy obtains. The reaction barriers show that the catalytic performance of trimetallic clusters are better than those of bimetallic clusters, and Pt2RuM clusters exhibit superior catalytic activity for O2 dissociation. The different performance of these alloy clusters for O2 dissociation is scrutinised with aid of molecular orbital and natural bond orbital population analysis.