Chun-Hua Zhen

Surface modification and electrocatalytic properties of Pt(100), Pt(110), Pt(320) and Pt(331) electrodes with Sb towards HCOOH oxidation

Abstract Behaviors of irreversibly adsorbed Sb adatoms on Pt(100), Pt(110), Pt(320) and Pt(331) single crystal surfaces and electrocatalytic properties of the modified electrodes towards formic acid oxidation were investigated. It was determined that Sb adatoms are stable at potentials below 0.45 V (SCE) on Pt(100) and Pt(110), below 0.40 V on Pt(320), and below 0.35 V on Pt(331). Different coverage of Sb ad was obtained conveniently by partially stripping Sb ad from saturation coverage of Sb ad . It has demonstrated that the redox behaviors of Sb adatoms and the coadsorption properties of Sb ad with H ad depend strongly on the orientations of the Pt single crystal electrode. Significant catalytic effects towards HCOOH oxidation were observed on Pt single crystal electrodes modified with Sb adatoms, which consist of (1) the inhibition of dissociative adsorption of HCOOH, (2) the enhancement of oxidation current, and (3) the negative shift of oxidation potential that was measured about 220 mV on Pt(110)/Sb, 110 mV on (110) sites of Pt(320)/Sb, and 100 mV on Pt(331)/Sb electrode. Neither enhancement of oxidation current nor negative shift of oxidation potential can be observed on Pt(100)/Sb electrode. The results suggested that electronic effect is the main effect presented on Pt(110), Pt(320) and Pt(331) surface upon Sb modification, while geometric effect is considered to the major effect on Pt(100) electrode.

Interaction of citrate with Pt(100) surface investigated by cyclic voltammetry towards understanding the structure-tuning effect in nanomaterials synthesis

This study aims to understand the effects of functional agents such as capping agents, stabilizers, surfactants and additives in shape-controlled synthesis of nanomaterials. The well-defined Pt(100) single crystal surface was used as a model to investigate its interaction with citrate, a capping agent that is often used in shape-controlled synthesis of nanomaterials. It demonstrated that, through a systematic study of electrochemical cyclic voltammetry, the presence of citrate in solution could increase the current peak density of hydrogen adsorption at high potential (jp,L), while decrease proportionally the current peak density of hydrogen adsorption at low potential (jp,S). Furthermore, the increase of citrate concentration shifted negatively the peak potentials (Ep,L and Ep,S) of both jp,L and jp,S. The results indicated that the interaction of citrate with Pt(100) surface could induce increasing the (100) surface domains of two-dimensional long range order (2D-(100)), and decreasing the (100) surface domains of one-dimensional short range order (1D-(100)). It also revealed that the interaction of citrate with Pt(100) surface could stabilize the 2D-(100) structure. The findings gained in this study implied that the citrate may lead to form stable 2D-(100) domains on Pt nanoparticles upon the shape-controlled synthesis of Pt nanomaterials.

In situ time-resolved FTIRS study of adsorption and oxidation of ethylene glycol on Pt(100) electrode

Adsorption and oxidation of ethylene glycol (EG) on Pt(100) electrode were studied by in situ time-resolved FTIRS (TRFTIRS). The TRFTIR spectra recorded at 0.10 V illustrate that an IR band appears near 2050 cm−1 at t > 5 s, corresponding to linearly bonded CO formed in dissociative adsorption of EG. The TRFTIR results have confirmed also that CO species are distributed uniformly on Pt(100) surface. Another band appears near 2342 cm−1 at t > 70 s, associating with IR absorption of CO2 produced in the direct oxidation of EG. With the increase of electrode potential, the direct oxidation of EG becomes gradually the main reaction. When the potential is above 0.40 V, the oxidation of EG occurs mainly via the reactive intermediates, i.e. species containing -COOH determined by in situ TRFTIRS.

Electrochemical Behavior of Irreversibly Adsorbed Sb on Au Electrode

Abstract The electrochemical processes of irreversibly adsorbed antimony (Sbad) on Au electrode were investigated by cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM). CV data showed that Sbad on Au electrode yielded oxidation and reduction features at about 0.15 V (vs saturated calomel electrode, SCE). EQCM data indicated that Sbad species were stable on Au electrode in the potential region from −0.25 to 0.18 V (vs SCE); the adsorption of Sb inhibited the adsorption of water and anion on Au electrode at low electrode potentials. Sb2O3 species was suggested to form on the Au electrode at 0.18 V. At a potential higher than 0.20 V the Sb2O3 species could be further oxidized to Sb(V) oxidation state and then desorbed from Au electrode.