Rational Design of Metal Oxide Nanostructures via Dopant Control: A Case Study in Photoelectrochemical Performance

On-demand material design is reshaping the synthesis landscape of multifunctional systems. In this scenario, the ability to tailor functional properties through deliberate control of composition and structure marks a significant advancement in materials science. Herein, a polymeric precursor solution method that enables spatially resolved dopant incorporation into oxide nanostructures is employed to design CuO, CeO₂, and α-Fe₂O₃ multifunctional systems. X-ray diffraction confirms the obtention of high-purity single-phase oxides. Further investigations using hematite (α-Fe₂O₃) as a model system demonstrate that lattice doping yields nanostructures with at least 2-fold increase in thickness and enhanced porosity, while modulating intragrain conductivity, as revealed by intensity-modulated photocurrent spectroscopy. Interfacial dopant segregation leads to smaller grains (from 28 to 19 nm), more compact morphologies, and lower energy barriers at grain boundaries, enhancing intergrain charge transport. Density functional theory supports this behavior, showing interfacial barrier reduction from 1.88 eV (pristine) to 1.31 eV (doped). Targeting photoelectrochemical performance, the combined use of lattice and interfacial doping induces synergistic changes in porosity, grain size, film thickness, and both intra- and intergrain conductivity. Through spatial control of dopant distribution, the PPS approach offers a versatile platform for the rational design of tunable metal oxides for energy, catalysis, and beyond.