The simultaneous optimization of the bulk and surface characteristics of photoelectrodes is essential to maximize their photoelectrochemical (PEC) performance. We report a novel one-pot hydrothermal synthesis of textured and surface-reconstructed BiVO₄ photoanodes (ts-BVO), achieving significant improvements in PEC water splitting. By controlling precursor molarity and ethylene glycol (EG) addition, we developed a stepwise dual reaction (SDR) mechanism, which enables simultaneous bulk texture development and surface reconstruction. The optimized CoBi/ts-BVO photoanode exhibited a photocurrent density of 4.3 mA∙cm⁻² at 1.23 V vs. reversible hydrogen electrode (RHE) with a high Faradaic efficiency of 98% under one sun illumination. Compared with nontextured BiVO₄, the charge transport efficiency increased from 8% to 70%, whereas the surface charge transfer efficiency improved from 9% to 85%. These results underscore the critical role of both bulk and surface engineering in enhancing PEC performance. Our findings offer a streamlined approach for improving the intrinsic properties of photoanodes in solar water splitting.

Spinel zinc ferrite (ZnFe₂O₄, ZFO) is a potential photoanode material for photoelectrochemical (PEC) water splitting because of its ideal bandgap (1.9–2.1 eV) and superior chemical stability in aqueous solutions. However, the low charge collection efficiency significantly hinders the improvement in PEC activity. Herein, we report an ultrafast and effective flame activation route to enhance the charge collection properties of ZFO. First, high-temperature flame (> 1300 ℃) facilitated surface and grain boundary diffusions, increasing the grain size and connectivity of the ZFO nanoparticles. Second, the reducing atmosphere of the flame enabled the formation of surface defects (oxygen vacancy and Fe²⁺), thereby increasing the charge carrier density and surface adsorption sites. Significantly, these two factors promoted charge transport and transfer kinetics, resulting in a 10-fold increase in the photocurrent density over the unactivated ZFO. Furthermore, we deposited a thin Al₂O₃ overlayer to passivate the ZFO surface and then the NiFeO_x oxygen evolution catalyst (OEC) to expedite hole injection into the electrolyte. This surface passivation and OEC deposition led to a remarkable photocurrent density of ~1 mA/cm² at 1.23 V versus the reversible hydrogen electrode, which is the highest value among all reported ZFO photoanodes. Notably, the NiFeO_x/Al₂O₃/F-ZFO photoanode achieved excellent photocurrent stability over 55 h (96% retention) and superior faradaic efficiency (FE > 94%). Our flame activation method is also effective in improving the photocurrent densities of other spinel ferrites: CuFe₂O₄ (93 times), MgFe₂O₄ (16 times), and NiFe₂O₄ (12 times).