Efficient acidic oxygen evolution reaction electrocatalyzed by iridium-based 12L-perovskites comprising trinuclear face-shared IrO6 octahedral strings

Development of cost-effective and highly active oxygen evolution catalysts operating well in acidic media is a critical challenge in proton exchange membrane water electrolysis.Herein,we present a class of iridium-based 12L-perovskites(Ba4MIr3O12;M=Pr,Bi,Nb)as novel low-iridium electrocatalysts for oxygen evolution reaction under acidic conditions.These 12L-perovskites contain trinuclear face-shared Ir O6octahedral strings—unique subunits that are not found in the previously-reported iridium-based electrocatalysts.The catalytic activities of 12L-perovskites(Ba4MIr3O12)are found to be related to the location of O 2p-band center,which is influenced by the B-site nonprecious element(i.e.,Pr,Bi or Nb).Our experimental results show that Ba4PrIr3O12is the most active electrocatalyst among the materials we synthesize,and contains 55%less iridium than the benchmark catalyst IrO2,while exhibiting higher catalytic activity.In the presence of Ba4PrIr3O12,transient leaching process of Ba and Pr takes place during electrochemical process,contributing to the surface reconstruction of the pristine catalysts.Further experimental results reveal that the formation of under-coordinated Ir Ox-rich surface and easier generation of active intermediate IrVare mainly responsible for the good activity of Ba4PrIr3O12.

An improved sensitivity non-enzymatic ascorbic acid sensor based on a Ag_2O nanowire modified Ag electrode

In this paper, the Ag2O nanowires had been prepared and applied for the fabrication of ascorbic acid sensors with high enhanced sensitivity by using self-assembly technology. The structures and morphologies of Ag2O nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The direct electrocatalytic oxidation of ascorbic acid in alkaline medium at Ag2O nanowires modified electrodes had been investigated in detail and the condition for determination of ascorbic acid was optimized, such as support-electrolyte, pH and scan speed. The oxidation peak current changed linearly with the concentration of ascorbic acid over the range from 2.0×10-8 mol/L to 1.0 mmol/L, and the detection limit can reach 1.0×10-8mol/L. Compared to a bare Ag electrode, a substantial decrease in the overvoltage of the ascorbic acid oxidation was observed at the Ag nanowires electrodes with oxidation starting at ca. 0.7V vs. Ag/AgCl (saturated KCl). The Ag2O nanowires modified electrode allows highly sensitive, low working potential, stable, and fast amperometric sensing of ascorbic acid, thus is promising for the future development of non-enzymatic ascorbic acid sensors.