In some examples, a fuel cell comprising a cathode, a cathode conductor layer adjacent the cathode, an electrolyte separated from the cathode conductor layer by the cathode, and an anode separated from the cathode by the electrolyte, wherein the anode, cathode conductor layer, cathode, and electrolyte are configured to form an electrochemical cell, and wherein at least one of cathode or the cathode conductor layer includes an exsolute oxide configured to capture Cr vapor species present in the fuel cell system.