An Ultra High Purity (UHP) carbon dioxide purification system and a method for purification of UHP carbon dioxide is disclosed. The purification system includes supported nickel oxide and supported palladium oxide. An upper portion of the purification system is at least partially filled with supported nickel oxide, and a lower portion of the purification system is at least partially filled with supported palladium oxide. The upper and lower portions of the purification system have a physical separation but are in fluid communication. The method includes purification or pre-purification of High Purity (HP) carbon dioxide to Ultra High Purity (UHP) levels including feeding carbon dioxide of High Purity grade or better to an Ultra High Purity carbon dioxide purification system.