外加偏压光-电转化效率(applied bias photon-to-current efficiency,abpe)是在一定偏压条件下,输入的太阳能与转化为氢能的比例[1]。
区别于太阳能制氢能转换效率(sth),abpe是扣除电能贡献的能量转化效率。
在研究单一光电极的pec分解水性能时,通常会使用外加电源施加较小偏压。此时,为评估光电极的光电转化效率,可由公式(1)简化为计算单一光阳极电解池的abpe公式:
通常情况下,在法拉第效率为100%的条件下,通过j-v曲线将jp、va和相应的pin带入公式(2)即可计算获得abpe。
对于单一光阴极电解池则采用公式(3)计算abpe:
由公式(2)可以发现,到当va取1.23 v时,abpe的值几乎为零,当va的取值>1.23 v(vs. rhe)时,abpe的值为负数,因此在测光阳极的光电流密度时尽量选择<1.23 v(vs. rhe)的外加偏压值,并应以提高外加偏压<1.23 v(vs. rhe)范围内的光电流密度为研究目标。
注意事项
计算时需要注意的以下两点:
①以上计算公式仅适用于单室光电反应池,即电极需要在同一电解液中,避免产生化学电势。
②电解质溶液中应不含电子或空穴牺牲试剂,虽然牺牲试剂可以很好的解决载流子在界面处的传输限制,但这将导致溶液中的反应复杂化,非原本的光电反应。
图1 abpe 曲线[2-5]
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