太阳能STEP过程Fe(Ⅲ)/ Fe(Ⅵ)电-燃料联产循环系统构建研究

Based on the intersection of four majorities of hot concepts- Solar Energy Utilization, Solar Fuel, Super Iron Battery and STEP (Solar Thermal Electrochemical process), the STEP-framed Solar Energy Rechargeable Cell, characterized with high energy and multi-electron transfer/redox cycle for efficient conversion of solar energy to electric energy combined with the synergistic production of solar fuel, is proposed and established in this application. Double-cell reaction system was constructed with the foundation of photothermal and photoelectric effect. The charging process was first carried out and then the discharging process. The Fe (III) was oxidized to Fe (VI) at the anode and hydrogen gas was generated at the cathode in Cell(I), while C and CO were generated in Cell(II) by the process of carbon capture; The electric energy released while the conversion of Fe (VI) to Fe (III) in Cell(I), while CO was generated continuously in Cell(II) by the process of carbon oxidation. The main contents are as follows :(1)Circulation was constructed by theoretical study and pattern construction.(2)The two key technologies were that the process control of Fe(III) oxidation to Fe (VI) and C oxidation to CO. A perfect pollution-free, sustainable STEP process was established, accomplishing the construction of solar cell-fuel combined cycle system by the cycle operation of charge and discharge process.

本项目以太阳能利用、STEP化学过程、超铁电池和太阳能燃料四个热点概念的交集为研究背景，以太阳能高效利用为目标，研究构建新型的Fe(Ⅲ)/Fe(Ⅵ)氧化还原电-燃料联产循环系统。利用太阳能光-热和光-电效应构建高温双池(Double-cell)反应体系，在Cell(I)中阳极将Fe(III)氧化到Fe(VI)，阴极生成H2，Cell(II)中利用CO2的碳捕捉过程生成C和CO，进行充电过程；在放电过程中，Cell(I)中Fe(Ⅵ)放电生成Fe(Ⅲ)，在Cell(II)中将C氧化持续生成CO。具体内容为（1）循环系统理论研究与构建研究；（2）关键技术研究：①Fe(III)氧化到Fe(VI)过程控制，②充电过程CO2还原生成C和CO过程控制和放电过程C氧化生成CO的过程控制。两过程能够在太阳能的驱动下循环进行，构筑了完美的、无污染的电-燃料联产新型太阳能利用系统。

项目将太阳能热电化学利用、可充熔盐超铁电池和太阳能燃料几个热点研究问题相结合，创新性的将STEP理论（Solar Thermal Electrochemical Process）应用于体系构建，使驱动此系统的能量完全来自于太阳能，利用Fe(III)和Fe(VI)之间的氧化还原反应的电势差构成循环体系，同时利用太阳能的光-热和光-电效应来实现太阳能STEP电池充放电循环过程与太阳能燃料的产出，系统正常运行后，具有高能量产出、可循环充放电和联产太阳能燃料等特点。在多能级相互配合条件下，实现太阳能高效应用，构筑了一个完美的无污染、可持续的太阳能循环利用系统。项目建立了STEP过程Fe(III)/Fe(VI)电-燃料联产系统，提出以高温熔融Fe2O3-NaOH-KOH、Li2CO3-Na2CO3-K2CO3分别作为Cell(I)单元和Cell(II)单元的电解质，详细探究了Cell(I)单元和Cell(II)单元中可能出现的电化学反应，系统在充电过程中，Cell(I)单元中碱金属氧化物还原生成H2，Cell(II)单元中完成对CO2的捕捉，生成微观形态呈纳米管型的C和CO，即生成太阳能燃料（Solar Fuel）。.通过对不同电解质配比、充电电流、充电时间、电解温度、电极材料等变量分析，测得的最佳条件下电池的平均的充电电压为3.4 V，开路电压为2.6 V，以100 Ω负载放电，高放电平台电压为1.8 V，低放电平台为电压为1.0 V，最高库伦效率为98.3%。STEP过程Fe(III)/Fe(VI)电-燃料联产系统具有理论比容量高、可充性好，高效利用太阳能等优点。系统高效地产出电能和化学能，为太阳能高效无污染循环利用提供了新思路。