Ethylenediamine-Controlled Morphological Evolution of Tapered Zn$_2$GeO$_4$ Bundles for Light-driven CO$_2$ Photoreduction

Morphology engineering stands as a cornerstone strategy to boost the light harvesting and charge transport properties of wide-bandgap oxide photocatalysts. Herein, a Zn$_2$GeO$_4$ photocatalyst with a highly symmetric conical bundle architecture is successfully fabricated via modulating the dosage of ethylenediamine (EDA). The introduction of a moderate EDA dosage effectively triggers the anisotropic growth of Zn$_2$GeO$_4$, thus constructing a compact and highly ordered conical bundle microstructure (denoted as 4-ZGO). This unique hierarchical morphology not only remarkably shortens the migration pathway of photogenerated charge carriers toward the catalyst surface, but also substantially suppresses bulk-phase charge recombination. Photoelectrochemical characterizations verify that 4-ZGO delivers superior performance in facilitating charge separation and efficient charge migration. As a result, 4-ZGO exhibits exceptional catalytic activity and robust operational stability for photocatalytic CO$_2$ reduction, affording an impressive 6-hour production yield of 34.97~$\mu$mol$\cdot$g$^{-1}$.