Effects of operating conditions on performance of high-temperature polymer electrolyte water electrolyzer

Abstract

Effects of operating conditions of a high-temperature polymer electrolyte water electrolyzer (HT-PEWE) on the electrolysis voltage are evaluated, and the optimal conditions for a high performance are revealed. A HT-PEWE unit cell with a 4-cm 2 electrode consisting of Nafion117-based catalyst-coated membrane with IrO2 and Pt/C as the oxygen and hydrogen evolution catalysts is fabricated, and its electrolysis voltage and high-frequency resistance are assessed. The cell temperature and pressure are controlled at 80-130 °C and 0.1-0.5 MPa, respectively. It is observed that increasing the temperature at a constant pressure of 0.1 MPa does not increase the ohmic overvoltage of the cell; however, it does increase the concentration overvoltage. It is also found that the increase in the overvoltage resulting from the rise in the temperature can be suppressed by elevating the pressure. When operating the cell at a temperature of 100 °C, pressure greater than 0.1 MPa suppresses the overvoltage, and so does pressures greater than 0.3 MPa at 130°C. This behavior suggests that keeping the water in a liquid water phase by increasing the pressure is critical for operating PEWEs at high temperatures.

Optimum structural properties for an anode current collector used in a polymer electrolyte membrane water electrolyzer operated at the boiling point of water

“…The costs and benefits of a PEMWE operating at high temperature are summarized as follows. An elevated temperature can (1) benefit heat recovery and thermal management, [13] (2) increase the efficiency of energy usage by accelerating the oxygen evolution reaction, [14][15][16][17][18][19][20][21][22][23][24] (3) reduce the amount of noble metal used and thus its cost, [16] and (4) allow for a compact structure for the PEMWE. [17] When the operating temperature increases beyond the boiling point of water, the two-phase flow in the cell will turn into a gas phase flow, which can easily be managed.…”

“…[20][21][22][23][24] Thus, to suppress the dehydration, the cell is pressurized to keep water in the liquid phase rather than in the gas phase. [20][21][22][23][24] However, the elevated pressure then requires a sealing material for the cell and a method to prevent gas leakage. [26] To exploit the advantages of higher temperatures while avoiding membrane dehydration, we propose increasing the temperature up to the boiling point of water.…”

“…When the temperature is near the boiling point, a disordered two-phase flow during the active phase change of water occurs [27][28] with the presence of liquid water expected to hydrate the membrane and thus suppress the high ohmic overvoltage. [21][22][23][24] In addition, increasing the temperature up to the boiling point does not require additional pressurization to keep water in the liquid phase, and thus the development of sealing materials is unnecessary.…”

Understanding the Role of Water Flow and the Porous Transport Layer on the Performance of Proton Exchange Membrane Water Electrolyzers

“…Furthermore, some authors have investigated the effect of other operating parameters (mainly pressure) on the total system overpotential. Some publications show a positive effect of pressure on performance at 0.6 15 and 2.5 A cm −2 ; 13 other articles show a varied effect of pressure with respect to current density at 1.5, 24 2, 14 and 1 A cm −2 ; 36 further works show a negavite effect of pressure on performance at 1, 35 1.3, 26 1, 31 1.25, 33 and 0.05 mA cm −2 . 40 Another study found an independence between pressure and mass transport losses up until 5 A cm −2 .…”

A Facile Strategy to Synthesize Cobalt‐Based Self‐Supported Material for Electrocatalytic Water Splitting

“…Electrocatalytic water splitting including two half‐reactions: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an efficient reliable technology to achieve mass production of high‐purity hydrogen with low cost and zero emission . The slow kinetics of water splitting and the high overpotentials necessitate high‐performance catalysts to decrease the electrolysis cell voltage and power consumption . However, the platinum‐ and iridium‐based catalysts are still the most active HER and OER catalysts and the low reserves and the high cost limits its application in large‐scale water splitting …”