Hydroxide Self‐Feeding High‐Temperature Alkaline Direct Formate Fuel Cells

Abstract Conventionally, both the thermal degradation of the anion‐exchange membrane and the requirement of additional hydroxide for fuel oxidation reaction hinder the development of the high‐temperature alkaline direct liquid fuel cells. The present work addresses these two issues by reporting a polybenzimidazole‐membrane‐based direct formate fuel cell (DFFC). Theoretically, the cell voltage of the high‐temperature alkaline DFFC can be as high as 1.45 V at 90 °C. It has been demonstrated that a proof‐of‐concept alkaline DFFC without adding additional hydroxide yields a peak power density of 20.9 mW cm −2 , an order of magnitude higher than both alkaline direct ethanol fuel cells and alkaline direct methanol fuel cells, mainly because the hydrolysis of formate provides enough OH − ions for formate oxidation reaction. It was also found that this hydroxide self‐feeding high‐temperature alkaline DFFC shows a stable 100 min constant‐current discharge at 90 °C, proving the conceptual feasibility.