Preparation Of YSZ Nano-arrays And Performance Of Solid Oxide Electrolysis Cell Stack

As an electrochemical all solid device that coverts the electricity into chemical energy, SOEC produces gaseous fuels through electrochemical processes with the high conversion efficiency. Currently SOEC features amorphous structure with porous complex ceramic materials, which results in serious problems such as strong electrochemical and concentration polarization, low conversion of reactant gases as well as short lifetime. In addition, the conventional SOEC consists of an YSZ electrolyte, a Ni-YSZ hydrogen electrode, a LSM-YSZ. However, LSCF has received widespread attentions in the case of LSCF showing a higher electrochemical activity and conductivity than LSM. So there are two parts in this work.The first one is about the preparation of ordered nanoscale electrolyte materials for the solid oxide electrolysis cell(SOEC). This research successfully synthesized ordered YSZ nanoarray by means of typical nanomaterials fabrication methods(such as hydrothermal, electrophoresis, sol-gel, and hot-press) and sacrificed template, which offers a good foundation for the preparation of nano-array electrodes.The second part of this work is that a 30-cell(10×10 cm2) LSCF-GDC(La0.6Sr0.4Co0.2Fe0.8O3-δ- Ce0.9Gd0.1O1.95) oxygen electrode and hydrogen electrode supported planar SOEC stack modules were manufactured and tested at different operation conditions(operating temperature, steam content, gas flow rate, et al) in steam electrolysis mode for hydrogen production. The i-v curves of each electrolysis were recorded and fitted according to the theoretical electrochemical models, the influences of operation conditions on the polarization loss of high temperature water electrolysis were analyzed, and the electrolysis efficiencies were calculated. High operating temperature gave the reduction of ohmic and electrochemical polarization, and high steam content resulted in significantly lowered electrochemical polarization. The flow rate of the gas onto the hydrogen electrode had great impact on concentration and electrochemical polarization. The influence of the concentration polarization under the conditions of gas introduced into the oxygen electrode can be ignored. However, the introduction of air would decline the electrochemicalpolarization of oxygen electrode obviously, whereasfed oxygen electrode with nitrogen could increase electrochemicalpolarization. By calculating the system efficiency of steam electrolysis under different experimental conditions, the result showshigh temperature, high steam concentration, high flow rates and fed oxygen electrode with air were contributed to the reducing polarization loss and energy demand for electrolysis, however, the energy for the heating gas were also increased at the same time. Compared the system efficiency under different experimental condition, the electrolysis efficiency could reach the maximal value of 80.8%(electrolysis voltage 1.273 V) when the system operating at 800℃, with 6 L·min-1 90% humidified hydrogen mixed gas, and the rate of resultant hydrogen was 4.57 L·min-1.