Stability of vapor phase water electrolysis cell with anion exchange membrane

Abstract

Highlights:  Similar initial water splitting activity was found in vapor and liquid phase operation.  In vapor-fed water electrolyzer a steady electric potential was achieved over a period of 90 h.  Water transport limitations were revealed to be a rate-determining factor.  Water contained in the membrane acts as a reservoir for water splitting.

Hydrogen generation from atmospheric water

“…4). 68,[72][73][74][75][76][77][78] Kumari et al 72 employed a vapor-fed PEM electrolyzer (Fig. 4a), supplying seawater-humidied air (80% RH) at the anode and dry nitrogen at the cathode.…”

“…Vapor-fed PEM/ AEM electrolysis systems face issues related to the availability of water molecules. 68,74,76 Humid gas has a signicantly lower H 2 O relative pressure compared to liquid water, which can cause increased voltage due to membrane dehydration and reduced conductivity. Hence, the ow rate and RH are critical factors.…”

Hydrogen Production from the Air

“…Direct saline splitting can produce hydrogen, which, however, faces a serious challenge of handling chlorine byproduct 10,11 . Some proton/anion exchange membrane electrolyzers can use vapor carried by inert gases as a feed; however, the electrolyzers must operate in an air-free atmosphere [12][13][14][15][16] .…”

Hydrogen production from the air

“…Direct saline splitting can produce hydrogen, which, however, faces a serious challenge of handling chlorine byproduct 10,11 . Some proton/anion exchange membrane electrolyzers can use high humidity vapor feed to the anode; however, the cathode of all of these electrolyzers must operate in an air-free atmosphere [12][13][14][15][16][17][18][19][20] , purged by an inert carrier gas such as nitrogen or argon, resulting in particularly low H 2 product purity of less than 2%. On another note, photocatalytic water splitting has a potential to use vapor feed 21 , but the biggest problem of this method is its low solar-to-hydrogen efficiency (around 1%) in real-world demonstrations 22,23 and to make it more complicated, the product is a mixture of H 2 and O 2 gases which require an extra separation process.…”