Surfaceenhanced Raman scattering (SERS) spectroscopy was used to explore the electrochemical reduction of CO, at a polycrystalline Ag electrode in KHCO, aqueous solution saturated with CO, at room temperature. Raman scattering from the oxidatioweduction cycled Ag electrode suggests the formation of CO and HCOOH by CO, reduction. At an electrode potential of 0.08 V (vs. Ag/AgCl), adsorbed CO gives rise to a C-O stretch band at 2128 cm-'. This band decreases in intensity and shifts to higher wavenumber with an increase of negative potential in the range from 0.0 to -0.24 V. A different potential dependence is observed for the C-H stretch mode of adsorbed HCOO-(2870 cm-' at -0.8 V). The O -C a antisymmetric and symmetric stretch modes of HCOO-observed at near 1550 and 1350 cm-' decrease in intensity with increasing negative potential, presenting a striking contrast to the C-H stretch mode. The SERS experiment with a C0,-saturated KHC0,-D,O solution is also described and discussed.

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The impact of large-scale grid-connected PV (photovoltaics) on power system transient stability is discussed in this paper. In response to an increase of PV capacity, the capacity of conventional synchronous generator needs to be reduced relatively. This leads to the lower system inertia and the higher generator reactance, and hence, the power system transient stability may negatively be affected. In particular, the impact on the transient stability may become more serious when the considerable amounts of PV systems are disconnected simultaneously during voltage sag. In this work, the potential impact of significant PV penetration on the transient stability is assessed by a numerical simulation using PSCAD/EMTDC.