Synergistic modulation of photogenerated electrons and holes of g-C₃N₄ especially achieved by simply modifying bimetallic species is highly desired for efficient photocatalytic CO₂ reduction. Herein, ultrasmall subnano Ni- and Mn-oxo clusters (average diameter of ≈0.8 nm) are uniformly anchored on tailored chitosan oligomer (COS)-functionalized ultrathin g-C₃N₄ nanosheets via OH and NH₂ in COS as the coordination sites. Optimized Ni and Mn comodified photocatalyst obtained by regulating bimetallic molar ratio exceptionally exhibits 22-times CO₂ conversion rate under solar-light irradiation and ≈20-times quantum efficiency at 405 nm light compared with pristine g-C₃N₄. By electron paramagnetic resonance, surface photovoltage spectroscopy, fluorescence spectra, photoluminescence spectra, and electrochemical curves, it is evidenced the enhanced photoactivities originate from the synergetic effect between Ni- and Mn-oxo species, capable of photoelectron-capture along with catalytic CO₂ activation and hole-capture along with catalytic H₂O activation, respectively. More importantly, due to the carrier-modulating capability difference, it is verified only a matching Ni:Mn molar ratio leads to the best charge separation then photoactivity as supported by the transient-state photoluminescence spectra. A new avenue to rationally modulate photogenerated charge carriers for fabricating efficient g-C₃N₄-based photocatalysts for solar-fuel production is proposed.

中文翻译：

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由壳聚糖低聚物锚定在二维 g-C3N4 上的协同亚纳米 Ni-和 Mn-Oxo 簇促进光催化 CO2 还原

gC ₃ N ₄的光生电子和空穴的协同调制尤其是通过简单地修饰双金属物质实现的，对于有效的光催化CO ₂还原是非常需要的。在此，超小型亚纳米 Ni- 和 Mn-氧簇（平均直径约为 0.8 nm）通过COS 中的 OH 和 NH ₂作为配位位点均匀锚定在定制的壳聚糖低聚物 (COS) 功能化超薄 gC ₃ N ₄纳米片. 通过调节双金属摩尔比获得的优化的 Ni 和 Mn 共改性光催化剂表现出 22 倍的 CO ₂与原始 gC ₃ N ₄相比，太阳光照射下的转化率和 405 nm 光下的量子效率约为 20 倍。通过电子顺磁共振、表面光电压谱、荧光光谱、光致发光光谱和电化学曲线，证明增强的光活性源于 Ni- 和 Mn-oxo 物种之间的协同作用，能够光电子捕获以及催化 CO ₂活化和空穴捕获以及催化 H ₂O 分别激活。更重要的是，由于载流子调制能力的差异，证实只有匹配的 Ni:Mn 摩尔比导致最佳的电荷分离，然后是由瞬态光致发光光谱支持的光活性。提出了一种合理调节光生载流子的新途径，以制备用于太阳能燃料生产的高效 gC ₃ N ₄基光催化剂。