Ultrasmall Abundant Metal-Based Clusters as Oxygen-Evolving Catalysts.

The oxygen evolution reaction is a crucial step in water electrolysis to develop clean and renewable energy. Although noble metal-based catalysts have demonstrated high activity for the oxygen evolution reaction, their application is limited by their high cost and low availability. Here we report the use of a molecule-to-cluster strategy for preparing ultrasmall trimetallic clusters by using the polyoxometalate molecule as a precursor. Ultrafine (0.8 nm) transition-metal clusters with controllable chemical composition are obtained. The transition-metal clusters enable highly efficient oxygen evolution through water electrolysis in alkaline media, manifested by an overpotential of 192 mV at 10 mA cm-2, a low Tafel slope of 36 mV dec-1, and long-term stability for 30 h of electrolysis. We note, however, that besides the excellent performance as an oxygen evolution catalyst, our molecule-to-cluster strategy provides a means to achieve well-defined transition-metal clusters in the subnanometer regime, which potentially can have an impact on several other applications.

Selective determination of dopamine in the presence of high concentration of ascorbic acid using nano-Au self-assembly glassy carbon electrode.

The cysteamine (CA) was bound onto surface of the pretreated glassy carbon electrode (GC) with cyclic voltammetry (CV). Gold nanoparticles were self-assembled to the electrode binding with cysteamine via strong Au-S covalent bond to fabricate the nano-Au self-assembled modified electrode (nano-Au/CA/GC). The modified electrode was characterized with cyclic voltammetric and ac impedance methods. The electrochemical behavior of dopamine (DA) on the modified electrode was investigated with cyclic voltammetry and differential pulse voltammetry (DPV). A well-defined redox peaks of DA on the nano-Au/CA/GC electrode were obtained at E(pa)=0.175 V and E(pc)=0.146 V (vs. SCE), respectively. The peak current of DA is linear with the concentration of DA in the range of 1.0 x 10(-8) mol L(-1) to 2.5 x 10(-5) mol L(-1), with the correlation coefficient of 0.998. The detection limit is 4.0 x 10(-9)mol L(-1) (S/N=3). The modified electrode exhibited an excellent reproducibility, sensibility and stability for determination of DA in the presence of high concentration AA, and can be applied to determinate dopamine injection, with satisfied result.