High-efficiency electrolysis of soluble K2CrO4 was realized in the CaCl2-KCl molten salt by adopting a novel anode structure. The carbon contamination due to the accumulation of carbon particles and CO32- reduction was very detrimental to the electrolysis process when a graphite anode was used, especially for the new process that soluble K2CrO4 was directly electrolyzed to metal Cr in the CaCl2-KCl molten salt. In this paper, the carbon migration and CO32- reduction during the K2CrO4 electrolysis were analyzed and discussed. The cathodic current distribution and the competing reduction reactions between CrO42- and CO32- were analyzed. The results indicated that the current efficiency for Cr production was only 45.7% for 12 h electrolysis. Dense carbon precipitations were found on the upper surface of molten salt, which led to the short circuit between anode and cathode. Therefore, the current efficiency is very low for Cr production. Meanwhile, competing reactions between CO32- and CrO42- took place, leading to high carbon contents in the cathode products. By adopting a novel anode structure, i.e. a graphite anode with a porous MgO shroud, the carbon precipitates were eliminated and the short circuit was effectively avoided. Resultantly, the current efficiency for Cr production increased greatly from 45.7% to 88.4% and the carbon content in the cathode products decreased from 2.47 wt% to 0.57 wt%. (C) 2017 The Electrochemical Society. All rights reserved.