TY - JOUR
T1 - Acceleration effect of thiourea on the oxidation reaction of hypophosphite ion on Ni surface
AU - Kunimoto, Masahiro
AU - Endo, Kazuaki
AU - Nakai, Hiromi
AU - Homma, Takayuki
N1 - Funding Information:
This work was partly funded by a Grant-in-Aid for Scientific Research (B) from The Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan , and it was carried out under the Global Center of Excellence (G-COE) Program, “Practical Chemical Wisdom,” of MEXT. Some of the present calculations were performed at the Research Center for Computational Science (RCCS), Okazaki Research Facilities, National Institutes of Natural Sciences (NINS).
PY - 2013/6/30
Y1 - 2013/6/30
N2 - The acceleration effect of thiourea on an electroless Ni deposition reaction was analyzed through experimental and theoretical approaches. In the experimental approach, the entire deposition process was physically separated into the anodic and the cathodic reactions by preparing two cells connected by a salt bridge. The cells contained either a bath without metal (Ni) ions or a bath without a reducing agent (hypophosphite ions). The current flowing between the two separated baths increased when thiourea was added only to the anodic reaction bath, which indicated that the acceleration effect of thiourea was mainly on the anodic reaction of the hypophosphite ions. Based on this experimental result, in the theoretical calculation approach, a co-adsorption system consisting of thiourea, hypophosphite, and a Ni metal surface was analyzed using density functional theory. Among all the elementary steps of a hypophosphite reaction, thiourea primarily should promote the adsorption step owing to the following two factors. One was the molecular interaction between thiourea and the hypophosphite ion. The other was the restructuring of the electronic states of the Ni surface owing to the adsorption of thiourea, which enhanced the interaction between hypophosphite and its adsorption site on the Ni surface.
AB - The acceleration effect of thiourea on an electroless Ni deposition reaction was analyzed through experimental and theoretical approaches. In the experimental approach, the entire deposition process was physically separated into the anodic and the cathodic reactions by preparing two cells connected by a salt bridge. The cells contained either a bath without metal (Ni) ions or a bath without a reducing agent (hypophosphite ions). The current flowing between the two separated baths increased when thiourea was added only to the anodic reaction bath, which indicated that the acceleration effect of thiourea was mainly on the anodic reaction of the hypophosphite ions. Based on this experimental result, in the theoretical calculation approach, a co-adsorption system consisting of thiourea, hypophosphite, and a Ni metal surface was analyzed using density functional theory. Among all the elementary steps of a hypophosphite reaction, thiourea primarily should promote the adsorption step owing to the following two factors. One was the molecular interaction between thiourea and the hypophosphite ion. The other was the restructuring of the electronic states of the Ni surface owing to the adsorption of thiourea, which enhanced the interaction between hypophosphite and its adsorption site on the Ni surface.
KW - Density functional theory
KW - Electroless Ni deposition
KW - Hypophosphite ion
KW - Thiourea
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U2 - 10.1016/j.electacta.2012.09.070
DO - 10.1016/j.electacta.2012.09.070
M3 - Article
AN - SCOPUS:84878015388
SN - 0013-4686
VL - 100
SP - 311
EP - 316
JO - Electrochimica Acta
JF - Electrochimica Acta
ER -