The oxidation processes of a Pt(111) electrode in alkaline electrolytes depend on non-specifically adsorbed ions according to in situ X-ray diffraction and infrared spectroscopic measurements. In an aqueous solution of LiOH, an OHad adlayer is formed in the first oxidation step of the Pt(111) electrode as a result of the strong interaction between Li(+) and OHad , whereas Pt oxidation proceeds without OHad formation in CsOH solution. Structural analysis by X-ray diffraction indicates that Li(+) is strongly protective against surface roughening caused by subsurface oxidation. Although Cs(+) is situated near the Pt surface, the weak protective effect of Cs(+) results in irreversible surface roughening due to subsurface oxidation.

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The electrochemical conversion of CO 2 to fuels such as CO and HCOO − is a highly attractive approach for decreasing the amount of greenhouse gases in the atmosphere and sustainable generation of valuable resources. Herein, electrocatalytic selectivities toward CO 2 reduction reaction over nanosized Pd−M (M = Zn, Cu, Sn, and Ag) bimetallic alloys were investigated. It was found that the selectivity for the products in the CO 2 reduction reaction depends on the effects of secondary elements, with Pd−Zn and Pd−Cu alloys showing formate selectivity and Pd−Ag 3 and Pd−Sn alloys showing CO selectivity. The faradic efficiency (FE) of HCOO − for PdZn NPs/CB was found to be significantly higher than that of the conventional Pd nanoparticles catalyst for the CO 2 reduction reaction at −0.1 V, and a record high FE of 99.4% at −0.1 V was also found. On the other hand, bimetallic PdAg 3 exhibits CO selectivity with a low overpotential and a much high FE (96.2% at −0.8 V) compared to Pd. The analysis of the center of the Pd d-band (i.e., d-band center) allowed us to rationalize the obtained high FE toward the CO 2 reduction reaction. We believe that this systematic effort will accelerate the development of novel highly selective and active electrocatalysts.

We revealed the promotive effect of alkali metal cations on Br adlayer formation on an Ag(100) electrode by in-situ measurement of the x-ray specular rod. Alkali metal cations in the electrical double layer affect the onset potential of Br adsorption and the order-disorder transition. We determined the Cs structure in the electrical double layer during Br adlayer formation and found that (1) the Cs structure depends on the coverage of adsorbed Br, and (2) the amount of Cs increases at the initial stage of Br adlayer formation. Structural analysis suggests that hydrated Cs is localized in the area around adsorbed Br via noncovalent interactions. Formation of a Cs-Br complex promotes Br adsorption.

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The effects of alkali meal cation on the surface oxidation and alcohol oxidation reactions on Au(111) have been investigated using surface X-ray diffraction and infrared spectroscopy. It is known that alkali metal cations strongly affect the alcohol oxidation reactions on Pt(111); however, the oxidation reactions on Au(111) do not depend on alkali metal cations. Infrared spectroscopy reveals the formation of adsorbed OH in LiOH and CsOH solutions below the second anodic peak at 1.3 V. This result indicates that surface oxidation processes do not depend on alkali metal cations below 1.3 V. The interfacial structure, including the outer layer, of an Au(111) electrode has been determined using X-ray diffraction in LiOH and CsOH. During the surface oxidation, the Au(111) surface in CsOH gets roughened more remarkably than that in LiOH above 1.3 V. Li + has a protective effect against surface roughening. Thus, the cationic effect is weaker in the potential region lower than the second anodic peak, which does not affect the lifting of the surface reconstruction and the alcohol oxidation reactions.

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