Unassisted photoelectrochemical (PEC) reactions, such as H₂ generation and CO₂ reduction, are limited by the durability of the immersed photoelectrode. Small band gap semiconductors, like Si, are efficient at utilizing a large portion of the solar spectrum but are not stable in aqueous environments without protection. While great strides have been made to improve stability under constant illumination, dark stability remains relatively unexamined and presents great challenges for durable PEC systems. Cathodic protection is an established electrochemical method for preventing metal electrode degradation in harsh conditions. Similar protection strategies cannot be applied to traditional two-terminal (2T) semiconductor photoelectrodes because of their inability to pass reverse bias current in the dark. New, three-terminal (3T) photovoltaic (PV) architectures introduce additional degrees of freedom in traditional 2T PEC operations by adding an extra electrical contact for an alternative low resistance path to protect the photoelectrode and drive electrochemical reactions, even in the dark. Here, we investigate bare 3T Si PV devices operating as photocathodes in aqueous methyl viologen electrolyte. The 3T architecture provides additional capabilities to PEC systems such as cathodic protection, the ability to drive reactions with or without illumination, and in situ switching between different operational modes. We show that 3T-based Si photocathodes maintain PEC activity after several hours of light/dark cycling. This work helps advance PEC use in real-world conditions where variable illumination must be considered.

中文翻译：

---

利用三端叉指背接触硅太阳能电池作为平台研究用于太阳能燃料生产的光电极的耐久性

无辅助光电化学（PEC）反应，例如H ₂生成和CO ₂还原，受到浸入式光电极的耐用性的限制。小带隙半导体，如硅，可以有效地利用大部分太阳光谱，但在没有保护的水环境中不稳定。虽然在提高恒定照明下的稳定性方面已经取得了长足的进步，但暗稳定性仍然相对未经检验，并对耐用的 PEC 系统提出了巨大的挑战。阴极保护是一种成熟的电化学方法，用于防止金属电极在恶劣条件下降解。类似的保护策略不能应用于传统的两端（2T）半导体光电极，因为它们无法在黑暗中通过反向偏置电流。新型三端 (3T) 光伏 (PV) 架构通过添加额外的电触点作为替代低电阻路径，在传统 2T PEC 操作中引入了额外的自由度，以保护光电极并驱动电化学反应，即使在黑暗中也是如此。在这里，我们研究了在水性甲基紫罗碱电解质中作为光电阴极运行的裸 3T Si PV 器件。 3T 架构为 PEC 系统提供了额外的功能，例如阴极保护、在有或没有照明的情况下驱动反应的能力，以及不同操作模式之间的原位切换。我们表明，基于 3T 的硅光电阴极在几个小时的光/暗循环后仍能保持 PEC 活性。这项工作有助于推进 PEC 在必须考虑可变照明的现实条件下的使用。