Spatiotemporal Mapping of Field‐Driven Electron Spillover across ZnO Facets

Abstract

ABSTRACT Efficient spatial separation of photogenerated charge carriers remains a formidable challenge in photocatalysis. Here, we employ in situ Kelvin probe force microscopy (KPFM) to reveal unexpected electron accumulation on nonpolar {010} facets in wurtzite ZnO platelets (N‐ZnO), which represents a dynamic “electron spillover” process beyond static facet confinement. Crucially, femtosecond transient absorption (fs‐TA) spectroscopy directly captures interfacial electron transfer from polar Zn‐terminated (0001) facets (Zn‐ZnO) to N‐ZnO with a lifetime of 60.82 ps. However, electrons spilling over from Zn‐ZnO to N‐ZnO recombine with the photogenerated holes inherent to N‐ZnO, thereby turning it into a recombination center. Guided by this insight, we construct a dual‐cocatalyst architecture (AuZnOCo): Au is selectively anchored on N‐ZnO and Zn‐ZnO to extract electrons, and Co 3 O 4 is deposited on O‐terminated (000) facets (O‐ZnO) to trap holes. The loading of dual cocatalysts promotes charge separation and suppresses this electron spillover‑induced recombination. Quantitative analysis reveals ≈3739 holes localized on O‐ZnO, ≈1771 electrons on Zn‐ZnO, and ≈812 electrons on N‐ZnO in AuZnOCo, while the electron diffusion length ( L ) increases from 81.41 to 121.77 nm. This work deciphers the spatiotemporal resolution of charge‐carrier dynamics, offering a blueprint for rationally engineering anisotropic photocatalysts.