Fig. 1. Representative IMPS and PEC data for hematite under monochromic illuminations (λ = 405 nm; intensity: 134 mW cm^–2). (a) Nyquist plots of the three bare samples, aH, sdH, and rgH, at an applied potential of 0.7 V vs. RHE (reversible hydrogen electrode). The sample IDs are explained in the main text. The two key parts in the plots used for data analysis are highlighted by arrows. The real and imaginary photocurrents are normalized to the high frequency intercept, which represents the hole flux toward the surface. (b) Using transfer efficiency extracted from IMPS data and the Gärtner equation, we obtained the photocurrent for ALD hematite (light green between squares), which is in agreement with the experimental steady-state current–voltage curve (dark green).