Nature.com has just posted this:

Researchers turn Atmospheric CO2 back into Coal.

From the article:

When CO2 was present in the electrolyte and a cerium-containing alloy was used, carbonaceous material could be produced which formed black floating debris in the electrolyte after prolonged electrolysis (Supplementary Fig. 4). The product was collected and purified for further analysis.
The I Fucking Love Science facebook page puts it in simpler terms:

The team used a liquid alloy made of gallium, indium, tin, and cerium. The liquid metal was stored in a glass tube with a wire running through it. Some water was added to the air in the glass tube. The pure CO2 was sent into the glass tube as electricity was sent down the wire. The team witnessed the formation of carbon flakes on the surface of the alloy. These could be removed to allow for the continuous capture of carbon.

The only by-products of the process are carbon flakes and pure oxygen. The carbon could just be buried back in the ground or used to produce carbon fiber materials, for example.
Seems like an interesting starting point for an alchemical application, and reminds me of the ‘lightning rod’, in which lightning is channeled into water held in a metallic vessel.