PECS cells TISES cell

Simple electroless techniques have been used for the formation of CdTe layers following an anodic or a cathodic route of deposition. For instance, spontaneous cathodic formation of CdTe was observed on Ti or glass electrodes short circuited with a corroding A1 contact (electron source) in a solution of Cd " " and HTe02 ions [96]. After thermal treatment and subsequent growth of an a-Pb02 layer on them, the as-obtained CdTe thin films were found to exhibit n-type behavior in alkaline polysulfide PEC cells. 

Before describing particular systems of PEC cells, let us formulate their main quantitative operating characteristics. The cell efiBciency ti is the ratio of the electric output power to the luminous input power, Pp The former is a product of photocurrent and photovoltage, Ip. Vph, and reaches its maximum value at a certain load resistance, R. Thus,... 

In Japan, a photoelectrochemical system for outdoor operation, i.e., solar, has been constructed. Photoanodes were Ti plates with a I fim thick Ti02 surface layer with a total area of 0.17 m, cathodes were of Pt, and the electrolyte was KCl. The result was an output of 1.1 1 of hydrogen per day, the conversion efficiency was about 0.4 % which is considered relatively high compared with the small absorption wavelength range (3 % of the entire solar spectrum) by Ti02 [25]. In a more recent effort using a multi-band gap PEC cell structure, an efficiency of 12.4 % has been achieved [3]. 

A newly-designed photoelectrocatalytic (PEC) reactor for CO2 reduction, which combines photocatalysis by Ti02 and electrocatalysis by carbon nanotubes (CNT), has recently been proposed (Fig. 7) [152]. A proton-conductive Nafion membrane connects the Ti02 and CNT. Irradiation of the combined system of nano-structured Ti02 deposited on a metal Ti electrode with Pt modified CNT deposited on carbon sheet caused water splitting to H2 and O2. A half-cell for the cathodic electrode, i.e., Pt or Fe modified CNT electrode, produces various organic molecules such as 2-propanol due to electrocatalytic reduction of CO2 on the electrode. The proposed PEC reactor is incomplete in its present state. However, these systems are expected to couple water splitting and CO2 reduction, and thus it may establish a new artificial photosynthetic system. 

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