Gas Crossover Regulation by Porosity-Controlled Glass Sheet Achieves Pure Hydrogen Production by Buffered Water Electrolysis at Neutral pH

Near-neutral pH water electrolysis driven by renewable electricity can reduce the costs of clean hydrogen generation, but its low efficiency and gas crossover in industrially relevant conditions remain a challenge. Here, it was shown that electrolyte engineering could suppress the crossover of dissolved gases such as O2 by regulating their diffusion flux. In addition, a hydrophilized mechanically stable glass sheet was found to block the permeation of gas bubbles, further enhancing the purity of evolved gas from water electrolysis. This sheet had a lower resistance than conventional diaphragms such as Zirfon due to its high porosity and small thickness. A saturated K-phosphate solution at pH 7.2 was used as an electrolyte together with the hydrophilized glass sheet as a gas-separator. This led to a near-neutral pH water electrolysis with 100 mA cm−2 at a total cell voltage of 1.56 V with 99.9 % purity of produced H2.