High differential pressure water electrolysis is a method that can replace the conventional high-pressure hydrogen production technology that uses normal pressure water electrolysis and a mechanical compressor. The differential pressure method requires a pressure resistant electrolysis cell, and the target hydrogen pressure is to be held by the proton exchange membrane. These issues were addressed by adjusting the strength and surfacial pores of the anode current collector and suppressing proton exchange membrane deformation, enabling the membrane to sustain a differential pressure of 35 MPa. Tests using a piston-type high differential pressure water electrolysis cell clarified that the optimum interfacial pressure between the current collector and the catalyst is 5 MPa. High-pressure hydrogen was successfully produced with a theoretical pressurization energy based on the concentration difference voltage by maintaining a constant interfacial pressure regardless of the hydrogen pressure inside the cell. In addition, it was confirmed that the current efficiency was 97%, the only loss was that due to hydrogen cross-permeation across the membrane, and that the cross-permeated hydrogen had no effect on other functions. Cross-permeation of oxygen was suppressed due to the differential pressure, and the oxygen concentration in the produced hydrogen was the specification value of 5 ppm or less. This means that the obtained hydrogen had a higher purity than that produced by normal pressure water electrolysis.
Article of Honda R&D Technical Review Vol.23 No.2 (97 - 105)