Read the article I linked to. It states that they used a silicon based semiconductor that doesn’t provide enough power. Next they are going to try a gallium-phosphide semiconductor which should produce better results. No mention of whether or not they will have to still add non sunlight energy to the mix then. Hey, if Orville and Wilber had as many nay sayers on their first 10 second flight at Kittyhawke we’d still be blimping it around the world. :)
Waste heat from coal plants?
Maybe place the converter portion of the device in the stack flow, beyond whatever sulfer squelchers are present; and place the solar cell portion on the outside, with wires & collector tubing as & where needed?
Even if it only worked during daylight hours on sunny days, it would still be a big drop in stack CO^2.
Do on-site conversion of the CO to fuel.