| Proton exchange membrane water electrolysis for hydrogen production has the ad-vantages of high energy density,high electrolysis efficiency,and high output pressure,and has a large development potential in the application scenario of coupling with differentscale renewable energy sources for hydrogen production and storage.Direct high-pressure electrolysis can reduce or even avoid the energy consumption caused by subsequent compression,thus enhancing the economics of hydrogen utilization.The economics of direct high-pressure electrolysis in high-pressure hydrogen pro-duction is investigated by modeling the cost of hydrogen in the electrolysis and compres-sion processes and analyzing the effects of different pressures,membrane thicknesses,and electricity prices on the energy efficiency of high-pressure hydrogen production.The economics of PEM and alkaline electrolysis are compared in the wind power coupling scenario,and the lower load limit makes the hydrogen cost of PEM electrolysis almost the same as that of alkaline electrolysis.The comprehensive energy efficiency analysis of high-pressure electrolysis provides data to support the development of direct high-pressure PEM electrolysis technology.Aiming at the problems of electrolyzer seal failure and deterioration of energy con-sumption due to high-pressure operation,a direct high-pressure electrolyzer and acces-sory system at atmospheric pressure on the oxygen side was designed and built?the effects of parameters such as temperature,circulating water flow rate,compression force and cathode pressure on the performance of high-pressure electrolyzer were analyzed experimentally.The electrolysis performance of 2 V@1.2 A/cm~2 is achieved at a pressure difference of 10MPa between cathode and anode.A zero-dimensional semi-empirical model of electrochemistry,mass transfer,and heat transfer in a singlecell electrolyzer is constructed,and the effects of pressure,temperature,and membrane thickness on electrolysis efficiency,hydrogen water content,and safety are analyzed based on the model,which provides a theoretical basis for the design,optimization and operation control of the actual electrolysis system.The transient response of the electrolyzer is predicted based on the equivalent circuit and polarization curve.The transient response under current control and voltage control is influenced by the doublelayer effect and mass transfer process and shows different response patterns under different amplitude and ranges of current density changes.The voltage variation during the shutdown process was observed and the causes were ana-lyzed,which should be controlled by open circuit voltage to avoid irreversible catalyst degradation.The voltage and current dynamics of the electrolyzer during load change and shutdown provide theoretical guidance for electrolysis load control in offgrid hydro-gen production scenarios.To address the safety risk and current efficiency degradation caused by more severe hydrogen crossover under high-pressure conditions,indirect in-situ measurements of hy-drogen crossover flux and current efficiency under differential pressure conditions are performed based on the hydrogen crossover mechanism model and mathematical model,and a suppression method of hydrogen concentration in oxygen is proposed.The current efficiency was found to decrease to 97.5% and the theoretical hydrogen concentration in oxygen increased to 4.5% at a differential pressure of 11.3 MPa.The degradation phenom-ena such as plastic deformation of internal components,catalyst layer fracture,and titanium element transfer triggered by high-pressure operation are also briefly discussed.The quantitative evaluation and suppression method of hydrogen crossover provides method-ological support for the optimization and operational safety of the high-pressure electrolyzer. |
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