Methyl-terminated p-type silicon photoelectrodes selectively drive CO₂ reduction by a homogeneous [Ru(tpy)(Mebim-py)(NCCH₃)]²⁺ catalyst (tpy = 2,2′:6′,2″-terpyridine, Mebim-py = 1-methylbenzimidazol-2-ylidene-3-(2′-pyridine)). A 460 mV photovoltage is quantified for the photoelectrode. Under 1 sun illumination, this system achieves a Faradaic efficiency of 87% for CO at −1.7 V vs Fc^+/0, matching reports of the same catalyst at metallic electrodes operating at −2.1 V. When 5% water is introduced, the CH₃-terminated Si photoelectrode remains stable, selectivity for CO is retained, and current density increases. Methyl termination suppresses the competitive hydrogen evolution observed for H-terminated Si photoelectrodes, which under the same conditions produce ca. 60% CO and 8% H₂ and have unstable performance. These results establish that a semiconductor photoelectrode can power a molecular CO₂ reduction catalyst without hydrogen evolution by the photoelectrode itself. Methyl termination of p-Si allows CO₂ reduction to kinetically outcompete proton reduction, revealing an important design principle for selective fuel formation.

中文翻译：

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p 型硅的甲基封端使得钌分子催化剂能够选择性光电化学 CO2 还原

甲基封端的p型硅光电极通过均相[Ru(tpy)(Mebim-py)(NCCH ₃ )] ²⁺催化剂(tpy = 2,2′:6′,2″-三联吡啶，选择性地驱动CO ₂还原， Mebim-py = 1-甲基苯并咪唑-2-亚基-3-(2′-吡啶))。光电极的光电压为 460 mV。在 1 个太阳光照下，该系统在 −1.7 V vs Fc ^+/0下实现了 87% 的 CO 法拉第效率，与在 −2.1 V 下运行的金属电极上相同催化剂的报告相匹配。当引入 5% 的水时，CH _3-封端Si光电极保持稳定，对CO的选择性得以保留，并且电流密度增加。甲基末端抑制了氢末端硅光电极观察到的竞争性析氢，在相同条件下产生约60%CO和8%H ₂，性能不稳定。这些结果证实半导体光电极可以为分子CO ₂还原催化剂提供动力，而光电极本身不会析出氢气。 p-Si 的甲基末端使得 CO ₂还原在动力学上胜过质子还原，揭示了选择性燃料形成的重要设计原理。