A redox flow battery comprising: an ionically conductive separator comprising a working side and a counter side ; a working side flowing electrolyte ; a working electrode in ionic contact with the working side of the ionically conductive separator and the working side flowing electrolyte ; a counter side flowing electrolyte ; a counter electrode in ionic contact with the counter side of the ionically conductive separator and the counter side flowing electrolyte ; an auxiliary electrode peripherally circumscribed by the working electrode in a common layer of the flow battery , wherein the auxiliary electrode is in ionic contact with the working electrode , the working side flowing electrolyte , and the working side of the ionically conductive separator ; an electrically insulating peripheral gap separating the auxiliary electrode from the working electrode ; a working electrode terminal conductively coupled to the working electrode ; an auxiliary electrode terminal conductively coupled to the auxiliary electrode ; a counter electrode terminal conductively coupled to the counter electrode ; and an auxiliary power source electrically connected to the auxiliary electrode terminal and the counter electrode terminal , wherein the auxiliary power source is configured to establish an auxiliary circuit voltage differential between the counter electrode terminal and the auxiliary electrode terminal , control an auxiliary electrode voltage such that the auxiliary electrode voltage is within an electrochemical window of the working side flowing electrolyte , and establish a voltage differential between the working electrode terminal and the auxiliary electrode terminal . an ionically conductive separator comprising a working side and a counter side ; a working side flowing electrolyte ; a working electrode in ionic contact with the working side of the ionically conductive separator and the working side flowing electrolyte ; a counter side flowing electrolyte ; a counter electrode in ionic contact with the counter side of the ionically conductive separator and the counter side flowing electrolyte ; an auxiliary electrode peripherally circumscribed by the working electrode in a common layer of the flow battery , wherein the auxiliary electrode is in ionic contact with the working electrode , the working side flowing electrolyte , and the working side of the ionically conductive separator ; an electrically insulating peripheral gap separating the auxiliary electrode from the working electrode ; a working electrode terminal conductively coupled to the working electrode ; an auxiliary electrode terminal conductively coupled to the auxiliary electrode ; a counter electrode terminal conductively coupled to the counter electrode ; and an auxiliary power source electrically connected to the auxiliary electrode terminal and the counter electrode terminal , wherein the auxiliary power source is configured to establish an auxiliary circuit voltage differential between the counter electrode terminal and the auxiliary electrode terminal , control an auxiliary electrode voltage such that the auxiliary electrode voltage is within an electrochemical window of the working side flowing electrolyte , and establish a voltage differential between the working electrode terminal and the auxiliary electrode terminal . <EOS>