3-D printed gradient porous composite electrodes improve anodic current distribution and performance in thermally regenerative flow battery for low-grade waste heat recovery

Abstract

A thermally regenerative flow battery (TRB) with 3-D porous Cu/C composite electrodes is constructed and its anodic current distribution is investigated with 5 anode electrode segments. It is demonstrated that there is a markedly uneven current distribution in a TRB with uniform porous electrodes (TRB-M), thereby limiting the maximum power generation. The contribution of each electrode segment to the total current decreases along the flow direction due to the high resistance of mass transfer and the increased consumption of ammonia during the reaction. The gradient porous electrodes have a significant influence on the distribution of the anodic current and the power generation of the TRBs. A TRB using a gradient porous electrode with decreasing pore diameter (TRB-LS) results in a more uniform anodic current distribution and a 17% increase in the maximum power compared to that of a TRB-M. Further improvements in the current distribution and performance of a TRB-LS are made by increasing the concentration of ammonia and the electrolyte flow rate by effectively enhancing mass transfer.