摘要/Abstract
液流催化燃料电池(LCFC)是一种可以在温和条件下转化生物质为电能的新型装置, 但其运行优化条件与相应机制尚不清晰. 本工作分析了阳极电解液的pH和温度对LCFC性能的影响规律. 其中, 极化曲线和功率密度曲线采用线性扫描伏安法测定, 以评估电池的产电性能; 阳极液的Mo5+浓度与总有机碳用于衡量有机底物与杂多酸的氧化还原反应进行的程度, 其中Mo5+浓度-吸光度标准曲线通过高锰酸钾滴定法和紫外-可见分光光度法确立; 阳极液中Mo的价态组成通过XPS谱图探索. 结果表明, 阳极液的适当酸化可以明显促进有机底物与杂多酸的氧化还原反应, 但过度酸化易导致杂多酸分解, 氧化性下降. 在强酸性条件(pH<1.5)下, 适当降低阳极液pH, 电池功率明显提高, 在pH为0.86时, LCFC最大功率密度达到峰值14.85 mW•cm–2, 比未酸化时提高1.24倍; 但pH过低时, 杂多酸分解, 氧化能力变弱, 电池功率降低. 在1.5≤pH≤7.5的范围内, pH对LCFC性能的影响较弱. 温度适当升高可以提升LCFC性能, 但过高温度会导致质子交换膜失水, 使质子传递过程受阻, 因此LCFC宜在80 ℃条件下运行.
关键词: 液流催化燃料电池, 开路电压, 功率密度, pH, 温度
Liquid-catalyst fuel cell (LCFC) is a novel device that can convert biomass to electricity directly under mild conditions, but its optimal operational parameters and corresponding mechanism have not been disclosed. In this study, the effect of anolyte pH and temperature on LCFC performance was analyzed comprehensively. Polarization curves and power density curves were measured using the linear sweep voltammetry to evaluate the power generation from LCFC. The Mo5+ concentration and total organic carbon in anolyte were measured to deduce the redox reaction between organics and heteropoly acid, and the Mo5+ concentration-absorbance standard curve was established using the potassium permanganate titration method and the ultraviolet visible spectrophotometry. The valence composition of Mo in anolyte was characterized using XPS spectra. The results demonstrated that a proper anolyte acidification significantly promoted the redox reaction between organic substrates and heteropoly acid, but an excessive acidification destroyed the structure of heteropoly acid and accordingly reduced its oxidizability. When the pH of anolyte was less than 1.5, the pH affected the power output of LCFC significantly. A moderate decrease of anolyte pH improved the power density greatly. At pH 0.86, the power density reached the maximum 14.85 mW•cm–2, which was 1.24 times higher than that without anolyte acidification. At extremely low pH, the power density deteriorated due to the decomposition of heteropoly acid and its weakened oxidizability. At the pH range of 1.5 to 7.5, the effect of pH on LCFC performance was relatively small. Moderate operational temperatures could enhance the performance of LCFC, but excessively high temperatures would dehydrate proton exchange membranes and consequently hindered proton transfer. Therefore, the temperature 80 ℃ was recommended for LCFC operation.
Key words: liquid-catalyst fuel cell, open circuit voltage, power density, pH, temperature
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