The effect of adding Bi3+ on the performance of a newly developed iron–copper redox flow battery

Daniel Manaye Kabtamu,Hwa-Jou Wei,Ning-Yih Hsu,Yi-Sin Chou,Hsin-Chih Huang,Guan-Yi Lin,Chen-Hao Wang,Yu-Chung Chang,Hsueh-Yu Chen

doi:10.1039/c7ra12926b

Abstract

In this paper, we propose a new, abundant, cost-effective, non-toxic, and environmentally benign iron–copper redox flow battery (Fe/Cu RFB), which employs Fe2+/Fe3+ and Cu+/Cu0 as the positive and negative electrolytes, respectively. The effect of graphite felt (GF) electrode modification and addition of Bi3+ into the electrolytes on the performance of the Fe/Cu RFB were investigated. It was found that the cell containing Bi3+ in the electrolytes revealed higher coulombic efficiency (89.18%) and energy efficiency (35.24%) than the cell without Bi3+ (CE = 84.10% and EE = 34.43%) at 20 mA cm−2. This is because after adding Bi3+, Cu metal precipitation was not observed on the electrode surface, which indicates that the deposition process was potentially reversible on the electrode material, thus leading to enhanced performance of the battery. Furthermore, the efficiencies of the battery are stable over 10 cycles, which demonstrates that Fe/Cu RFB exhibits good stability on the microwave heat treated GF plus one layer microwave heat treated carbon paper (HT-GF + HT-CP) electrode after adding Bi3+ into the electrolytes.

Highlights

Due to the environmental concerns over burning of fossil fuels and their limited resources, along with the rising energy demands for the increasing global population, the utilization of clean and renewable energy generated from renewable sources, such as wind and solar, have attracted considerable social and scienti c attention in recent years
A er adding Bi3+ into the electrolytes, the efficiencies of the battery are stable over 10 cycles, which demonstrates that Fe/Cu RFB has a good stability on the microwave heat treated graphite felt plus one layer microwave heat treated carbon paper (HT-GF + HT-CP) electrode under these conditions
This is because the presence of Bi3+ avoids precipitation of Cu metal on the electrode surface, which indicates that the electrodeposition process is potentially reversible on the electrode material, leading to enhanced performance of the battery

Summary

Introduction

Due to the environmental concerns over burning of fossil fuels and their limited resources, along with the rising energy demands for the increasing global population, the utilization of clean and renewable energy generated from renewable sources, such as wind and solar, have attracted considerable social and scienti c attention in recent years. Among the numerous types of RFBs that have been reported to date,[12,13] all-vanadium redox ow batteries (VRFBs), originally proposed by Skyllas-Kazacos et al.,[14] are highly suitable and widely studied for large-scale energy storage systems because of the good electrochemical reversibility of vanadium redox couples They use active species of the same vanadium metal as the electrolytes, which substantially minimizes the problem of active component crossover contamination across the membrane.[15,16] the limited earthabundance and high cost of vanadium and the relatively low energy efficiency of the VRFBs still hinder their widespread commercial adoption.[6] A feasible strategy to reduce the cost of RFBs should be considered in terms of materials, cell con gurations, and fabrication processes. 1280C) at a current density of 20 mA cmÀ2 within a xed potential range of 0–1.2 V

Preparation of electrolytes

Electrochemical measurements

Results and discussion

Conclusions