Water splitting using a semiconductor photocatalyst has been extensively studied as a means of solar-to-hydrogen energy conversion. Powder-based semiconductor photocatalysts, in particular, have tremendous potential in cost mitigation due to system simplicity and scalability. The control and implementation of powder-based photocatalysts are, in reality, quite complex. The identification of the semiconductor–photocatalytic activity relationship and its limiting factor has not been fully solved in any powder-based semiconductor photocatalyst. In this work, we present systematic and quantitative evaluation of photocatalytic hydrogen and oxygen evolution using a model strontium titanate powder/aqueous solution interface in a half reaction. The electron density was controlled from 10¹⁶ to 10²⁰ cm^–3 throughout the strontium titanate powder by charge compensation with oxygen nonstoichiometry (the amount of oxygen vacancy) while maintaining its crystallinity, chemical composition, powder morphology, and the crystal and electronic structure of the surface. The photocatalytic activity of hydrogen evolution from aqueous methanol solution was stable and enhanced by 40-fold by the electron doping. The enhancement was correlated well with increased Δabsorbance, an indication of prolonged lifetime of photoexcited electrons, observed by transient absorption spectroscopy. Photocatalytic activity of oxygen evolution from aqueous silver nitrate solution was also enhanced by 3-fold by the electron doping. Linear correlation was found between the photocatalytic activity and the degree of surface band bending, ΔΦ, above 1.38 V. The band bending, potential downhill for electronic holes, enlarges the total flux of photoexcited holes toward the surface, which drives the oxygen evolution reaction.

中文翻译：

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均质电子掺杂到非化学计量的钛酸锶中可提高其对氢和氧的光催化活性

使用半导体光催化剂进行的水分解已被广泛研究作为太阳能转化为氢能的手段。特别地，由于系统的简单性和可扩展性，基于粉末的半导体光催化剂在降低成本方面具有巨大的潜力。实际上，粉末基光催化剂的控制和实施非常复杂。在任何基于粉末的半导体光催化剂中，尚未完全解决半导体与光催化活性关系及其限制因素的鉴定问题。在这项工作中，我们目前使用模型钛酸锶粉末/水溶液界面在半反应中对光催化氢和氧的放出进行系统和定量的评估。电子密度控制在10 ¹⁶至10 ²⁰厘米^–3通过氧非化学计量（氧空位的数量）进行电荷补偿，同时保持其结晶度，化学成分，粉末形态以及表面的晶体和电子结构，从而对整个钛酸锶粉末进行补偿。从甲醇水溶液中析出的氢的光催化活性是稳定的，并且通过电子掺杂提高了40倍。这种增强与瞬态吸收光谱法观察到的增加的Δ吸光度密切相关，Δ吸光度是光激发电子寿命延长的指示。通过电子掺杂，从硝酸银水溶液中析出的氧气的光催化活性也提高了3倍。发现在1.38 V以上，光催化活性与表面能带弯曲度ΔΦ之间存在线性关系。