磷钼酸作为低温碳燃料电池的碳间接电氧化介质

以磷钼酸作为低温下碳间接电氧化的介质构建新型碳燃料电池。通过线性电位扫描和计时电流法研究不同碳材料、不同反应条件、不同反应时间、不同磷钼酸浓度对碳间接电氧化性能的影响。采用循环伏安法研究碳在磷钼酸介质中的间接电氧化机理。研究结果表明,椰壳活性炭的间接电氧化活性要明显高于煤和煤质活性炭。以磷钼酸为介质时,采用光照与升温80oC避光的条件均可以提高碳间接电氧化性能,且提高程度接近。由循环伏安测试分析出磷钼酸中+6价Mo可将碳氧化,且被还原成+5价Mo,随后又在阳极上重新被电氧化回+6价Mo,通过该过程将从碳材料上获得的电子转移到阳极上,从而实现碳在低温条件下的间接电氧化过程。并且通过对光照条件的分析,证实光对磷钼酸催化碳电氧化反应有两方面的促进作用:一方面光的热效应使反应温度升高,从而提高反应速率;另一方面磷钼酸利用其特有结构吸收光能,提高磷钼酸与碳的反应速率,且后者促进作用更明显。以VO2+/VO2+为阴极构建的碳燃料电池全电池室温下功率是0.087m W?cm-2,验证了碳燃料电池在常温条件下运行的可行性。

Phosphomolybdic Acid as a Mediator for Indirect Carbon Electrooxidation in LowTemperature Carbon Fuel Cell

Phosphomolybdic acid was investigated as a mediator for indirect carbon electrooxidation at low temperatures. Linear sweeping voltammetry and chronoamperometry experiments showed that the carbon electrooxidation process was influenced by the type of carbonaceous material, reaction conditions, reaction time, and phosphomolybdic acid concentration. The mechanism underlying indirect carbon electrooxidation was explored using cyclic voltammetry. The results showed that the reactivity of coconut-derived activated carbon was higher than that of coal-derived activated carbon or coal in the chemical reaction between phosphomolybdic acid and carbon materials. Sunlight and heating to 80℃ similarly improved the efficiency of the indirect carbon electrooxidation. The electrooxidation mechanism is as follows:Mo^VI in phosphomolybdic oxidizes carbon to form Mo^V, and is then electrooxidized back to Mo^VI in an anodic reaction, releasing the electron obtained from the carbon material. This process facilitated the indirect electrooxidation of carbon at low temperatures. Sunlight was found to enhance the rate of the chemical reaction between phosphomolybdic acid and carbon materials in two ways:1) thermally by increasing the reaction temperature and thus improving the reaction rate; 2) photocatalytically, as sunlight absorbed by phosphomolybdic acid is converted into chemical energy, which is the main effect. A full cell test with phosphomolybdic acid demonstrated a power density of 0.087 mW·cm^-2 at room temperature, indicating that the concept of low-temperature carbon fuel cells is feasible.