Visualizing Facet-Dependent Heterogeneity and Carrier Transport in Semiconductors Using Scanning Electrochemical Cell Microscopy

Advancing technologies for sustainable energy production and storage will require an improved understanding of the relationships between material structure and interfacial charge transport. Materials employed in these applications are often heterogeneous, exhibiting structural defects which may influence carrier transport and recombination in these systems. Conventional experimental techniques are often unable to provide insights into the role played by these defects due to their limited spatial resolution. Here, we apply scanning electrochemical cell microscopy (SECCM) to visualize and quantify carrier transport in faceted BiVO₄ crystals, revealing valuable insights into the facet-dependent reactivity in this system. Using SECCM, higher photocurrents are observed at {110} facets vs. {010} and {111} facets, attributable to anisotropic carrier transport within the system. Carrier generation-tip collection SECCM imaging further revealed a pronounced asymmetry in charge carrier dynamics, wherein photogenerated holes exhibit long-range lateral diffusion. Electrons were suppressed at the illuminated facet but instead underwent lateral transport to displaced regions—behavior indicative of facet-specific charge separation. The results demonstrate the unique quantitative capability of scanning electrochemical cell microscopy to advance the understanding and design of next-generation electrochemical materials at the nanoscale level.