Seawater usable for production and consumption of hydrogen peroxide as a solar fuel

Abstract

Hydrogen peroxide (H2O2) in water has been proposed as a promising solar fuel instead of gaseous hydrogen because of advantages on easy storage and high energy density, being used as a fuel of a one-compartment H2O2 fuel cell for producing electricity on demand with emitting only dioxygen (O2) and water. It is highly desired to utilize the most earth-abundant seawater instead of precious pure water for the practical use of H2O2 as a solar fuel. Here we have achieved efficient photocatalytic production of H2O2 from the most earth-abundant seawater instead of precious pure water and O2 in a two-compartment photoelectrochemical cell using WO3 as a photocatalyst for water oxidation and a cobalt complex supported on a glassy-carbon substrate for the selective two-electron reduction of O2. The concentration of H2O2 produced in seawater reached 48 mM, which was high enough to operate an H2O2 fuel cell.

Fuel Production from Seawater and Fuel Cells Using Seawater

“…Reviews spect to the value of flat band potential of WO 3 (0.09 Vv s. SCE at pH 1.3). [116] When pure water was replaced by seawater under otherwise the same reactionc onditions, roughly four times larger ap hotocurrentw as detected at 0.3 Vv s. SCE and the onset potential was negatively shiftedf rom 0.2 Vv s. SCE to 0.1 Vv s. SCE as compared to those in pure water. [116] The catalytic current for the two-electronr eduction of O 2 with [Co II (Ch)]/CP at pH 1.3 in seawatera ppearsa ta round0 .25 Vv s. SCE, which is nearly the same as the value measured at pH 1.3 in pure water (Figure 14 b).…”

“…[116] The photoirradiation of m-WO 3 /FTO with as olar simulator (1 sun = AM 1.5G) in the anode cell resulted in formation of H 2 O 2 in the cathode cell of the two-compartment photoelectrochemical configuration with no externalb ias potentialb eing applied. [116] The time courses of the photocatalytic formation of H 2 O 2 are shown in Figure 13. [116] reported to catalyze the selective two-electron/two-proton reductiono fO 2 to yield H 2 O 2 efficiently.…”

“…[116] The time courses of the photocatalytic formation of H 2 O 2 are shown in Figure 13. [116] reported to catalyze the selective two-electron/two-proton reductiono fO 2 to yield H 2 O 2 efficiently. [114,115] After illumination for 24 h, the concentration of H 2 O 2 produced in seawater was 48 mm (blue circles in Figure 13), which is high enough to operate an H 2 O 2 fuel cell (see below).…”

“…[116] However,the production of H 2 O 2 is much decelerated when pure water was used instead of seawater for the photocatalyticH 2 O 2 production ( Figure 13). [116] The similare nhancement of the photocatalytic H 2 O 2 production is observedw hen seawaterisreplaced by an NaCl solution with the same concentrationa st hat of seawater (blue squares in Figure 13). The effects of Cl À on photocatalytic H 2 Oo xidation with m-WO 3 /FTOa nd the two-electron reduction of O 2 with [Co II (Ch)]/CP were studied by using ap hotoelectrochemical cell with athree-electrode configuration (see below).…”

“…The effects of Cl À on photocatalytic H 2 Oo xidation with m-WO 3 /FTOa nd the two-electron reduction of O 2 with [Co II (Ch)]/CP were studied by using ap hotoelectrochemical cell with athree-electrode configuration (see below). [116] The current-potential curveso fm-WO 3 /FTO under simulated solar illumination (1 sun = AM 1.5G) are compared to those in dark in Figure 14 a, where the onset of photocurrent for the H 2 Oo xidation is observed at 0.2 Vv s. SCE at pH 1.3 in pure water,w hich corresponds to the 110mVoverpotential with re- Figure 11. Time profiles for (a) conversion of H 2 S, (b) H 2 mole fraction, and (c) S 2 mole fraction for feed containing5mol %H 2 Si nA ru nder1bar pressure at different temperatures.…”