Performance Evaluation of a Hydrogen-Vanadium Reversible Fuel Cell

Abstract

Hydrogen-vanadium reversible fuel cells were tested using a Pt/C hydrogen electrode, carbon vanadium electrode and interdigitated flow fields at both electrodes. Vanadium electrolyte flow rate was varied to study its effect on mass transport performance. Two types of vanadium electrodes were explored, a single layer of high surface area carbon nanotube (CNT) electrode and three layers of nitric acid-treated carbon paper. Finally, four types of Nafion membranes were examined to determine the effect of membrane type and thickness on fuel cell charge and discharge performance. Higher performance was observed with higher vanadium flow rate, thinner membranes and a CNT vanadium electrode. Peak power density of greater than 540 mW/cm 2 was obtained using a NR212 membrane and CNT vanadium electrode. © The Author Hydrogen-vanadium fuel cells offer a feasible solution for storing electrical energy from the grid or directly from renewable energy sources such as wind and solar.1 In a hydrogen-vanadium reversible fuel cell, the charge and discharge reactions are as follows:Overall Reaction :.99 V While charging, a hydrogen-vanadium fuel cell stores energy in the form of hydrogen and vanadium (V). During discharge, hydrogen is consumed at the negative electrode and vanadium (V) is reduced to vanadium (IV) at the positive electrode. Vanadium systems demonstrate no issues with membrane fouling or metal dendrite formation (e.g. iron and zinc electrode systems).2,3 Additionally, vanadium solutions have low volatility, low corrosivity, and do not produce toxic vapors. 4,5 In particular, cells that utilize chlorine or bromine pose a significant safety concern due to their high vapor pressures and toxic properties. [6][7][8] Due to the relatively high cost of vanadium, the hydrogen-vanadium fuel cell is attractive over the all-vanadium system due to the 50% reduction in the amount of vanadium solution required. Since the cost of the vanadium electrolyte for the all-vanadium flow battery makes up roughly 40% of the total system cost, cutting the vanadium electrolyte requirement by half has a large impact on reducing the overall system cost.1 Another benefit of a mixed gas/liquid electrolyte system (hydrogen gas at the negative electrode and liquid vanadium at the positive electrode) is the ease of separation if crossover occurs. Unfortunately, one of the major disadvantages of the hydrogen-vanadium system compared to the all-vanadium sys- * Electrochemical Society Student Member. * * Electrochemical Society Fellow. z E-mail: cptvn@ku.edu tem is that a precious metal catalyst is required for HOR/HER at the hydrogen electrode. Past research by Yufit et al. has shown the feasibility of the hydrogen-vanadium fuel cell and the importance of vanadium electrode wettability on fuel cell performance. 9 The wettability of the vanadium electrode is important for two reasons. First, only wetted area or area with access to the electrolyte is active, and second, a more wetted porous electrode allows vanadium electrolyte to more easily flow into a...

Hydrogen/functionalized benzoquinone for a high-performance regenerative fuel cell as a potential large-scale energy storage platform

“…Amongst the organic redox materials reported in the literature, the redox potential of BQDS is relatively high and this may mean that applying an electrode with a large surface area/ porosity in a high concentration of the electrolyte is expected to result in high current and power densities. As a consequence, we coupled this redox species with the hydrogen evolution/ oxidation reaction (HER/HOR) that is widely being studied in the literature 15,17,56 for RFC applications.…”

“…[11][12][13][14] However, vanadium is a rare element so the capital cost of the redox material is a big obstacle for the large-scale commercialisation of the VRFB. [15][16][17][18][19] The energy cost of a VRFB is $320 per kW h whilst the target set by the U.S. Department of Energy (DOE) is $100 per kW h, with almost 50% of the price being dominated by the cost of the electrolyte. 20,21 In response to the price sensitivity of vanadium, various redox-active species have been investigated and suitable ones tailored to lower the cost of RFB redox materials.…”

Characterization of a Regenerative Hydrogen-Vanadium Fuel Cell Using an Experimentally Validated Unit Cell Model

“…This higher performance could be attributed to an improved transport of active species to and from the porous electrode. Dowd et al 13 reported similar performance at an initial SOC of 90% with a cell configuration consisting of a carbon paper cathode, a Pt coated carbon paper anode and a N115 membrane. A peak power density of 1680 W m −2 at a current density of 2700 A m −2 and a limiting current density above 3500 A m −2 for a flow rate of vanadium electrolyte of 12 mL/min were reported.…”

A Hydrogen-Vanadium Reversible Fuel Cell Crossover Study

“…A fuel cell startup procedure was carried out to ensure the membrane was properly hydrated prior to testing. The startup procedure consisted of cycling the fuel cell between discharge (0.6 V) and charge modes (1.3 V) every 10 min for more than 12 h. 8 Polarization curves were obtained for the EBN membranes in order to compare their performance to our previously published results for NR211, NR212, N115 and N117. 8 Charge and discharge polarization curves were obtained using a constant voltage staircase mode with 50 mV increments every 2 min.…”