Hydrogen-Chlorate Electric Power Source: Feasibility of the Device, Discharge Characteristics and Modes of Operation

Abstract

A power source based on the current-generating reaction of aqueous chlorate-to-chloride reduction by molecular hydrogen would provide as much as 1150 Wh per 1 L of reagent storage (for a combination of 700 atm compressed hydrogen and saturated aqueous solution of lithium chlorate) at room temperature, but direct electroreduction of chlorate only proceeds with unacceptably high overvoltages, even for the most catalytically active electrodes. In the present study, we experimentally demonstrated that this process can be performed via redox-mediator catalysis by intermediate products of chlorate reduction, owing to their participation in homogeneous com- and disproportionation reactions. A series of current–voltage and discharge characteristics were measured for hydrogen-chlorate membrane–electrode assembly (MEA) cells at various concentrations of chlorate and sulfuric acid under operando spectrophotometric monitoring of the electrolyte composition during the discharge. We established that chlorine dioxide (ClO2) is the key intermediate product; its fraction in the electrolyte solution increases progressively, up to its maximum, equal to 0.4–0.6 of the initial amount of chlorate anions, whereas the ClO2 amount decreases gradually to a zero value in the later stage. In most discharge experiments, the Faradaic yield exceeded 90% (maximal value: 99%), providing approximately 48% chemical energy storage-to-electricity conversion efficiency at maximal power of the discharge (max value: 402 mW/cm2). These results support prospect of a hydrogen-chlorate flow current generator as a highly specific energy-capacity source for airless media.

Reversible Chlorite/Chlorine Dioxide Anion Redox Couple for Low-Cost Energy Storage

“…The chlorite/chlorine dioxide redox has also recently been implicated in the electroreduction of chlorate, including in hydrogen-chlorate primary batteries. 11,12 Simple electron transfer is advantageously used for several transition metal cations used as redox-active battery electrodes in aqueous solution (e.g., Fe(II)/Fe(III), V(II)/V(III), V(IV)/V(V), Cr(II)/Cr(III), Ce(III)/Ce(IV), etc. ), particularly in flow batteries.…”

Reversible Chlorite Anion/Chlorine Dioxide Redox Couple for Low-Cost Energy Storage

“…We reasoned that this reaction, ClO 2 – ↔ ClO 2 + e – , might be highly reversible because only electron transfer, rather than atomic bond breaking or formation (e.g., as in chlorine oxidation 2Cl – ↔ Cl 2 + 2e – ) is required, and a previous study indicates that this is the case. The chlorite/chlorine dioxide redox has also recently been implicated in the electroreduction of chlorate, including in hydrogen–chlorate primary batteries. , Simple electron transfer is advantageously used for several transition-metal cations used as redox-active battery electrodes in aqueous solution (e.g., Fe­(II)/Fe­(III), V­(II)/V­(III), V­(IV)/V­(V), Cr­(II)/Cr­(III), Ce­(III)/Ce­(IV), etc. ), particularly in flow batteries .…”

“…The chlorite/chlorine dioxide redox has also recently been implicated in the electroreduction of chlorate, including in hydrogen−chlorate primary batteries. 11,12 Simple electron transfer is advantageously used for several transition-metal cations used as redoxactive battery electrodes in aqueous solution (e.g., Fe(II)/ Fe(III), V(II)/V(III), V(IV)/V(V), Cr(II)/Cr(III), Ce(III)/ Ce(IV), etc. ), particularly in flow batteries.…”