Photoelectrolytically-desiccating multiple-glazed window units

A multiple-glazed window unit having at least two sheets and a means to space said sheets from one another to provide an airspace between the sheets, the improvement comprising:

• a) a photoelectrolytically-desiccating coating deposited over at least a portion of a first surface of the unit exposed to the airspace and subject to the accumulation of moisture present in the airspace thereon, whereupon said photoelectrolytically-desiccating coating promotes the photoelectrolysis of said accumulated moisture from said first surface primarily into hydrogen gas and oxygen gas;
• b) at least one hydrophilic coating associated with said photoelectrolytically-desiccating coating to increase contact between said moisture present in the airspace and the photoelectrolytically-desiccating coating;
• c) a photocatalytically-activated self-cleaning coating over at least a portion of a second surface of the unit exposed to the airspace and subject to the accumulation of organic surface contaminants present in the airspace thereon whereupon said photocatalytically-activated self-cleaning coating promotes the photocatalytic decomposition of said organic surface contaminants primarily into carbon dioxide and water vapor, wherein said first surface and said second surface may be the same or a different surface;
• and
• d) a sodium ion diffusion barrier layer interposed between a source of sodium ions and a coating selected from the group consisting of said photoelectrolytically-desiccating coating and said photocatalytically-activated self-cleaning coating to prevent sodium ion poisoning of said coating.