Aligning the Facet-Oriented Electric Field via Facet-Selective Doping on Truncated SrTiO₃ Nanoparticles for Photoinduced Carrier Migration and Hydrogen Evolution

The intrinsic driving force of semiconductor-based photocatalysts for separation and transfer of photoexcited charge carriers is still insufficient kinetically. The establishment and enhancement of an internal electric field within single particles are effective approaches to accelerate carrier migration with the introduction of symmetric breaking. In our work, a facet-selective doping strategy is proposed as the synergetic combination of the asymmetric facet effect and doping effect on truncated {100} and {110} SrTiO₃ single nanoparticles as the model, which is realized via facet-selective photodeposition and facet-domain doping methods. For {100} facets, Rh doping with aliovalent Rh³⁺ substituted for Ti⁴⁺ after Rh valence regulation leads to p-type transformation compared to pristine n-type {110} facets without doping, resulting in the opposite shift of the surface band bending direction within the space charge region. Due to facet-selective p-type transformation, surface electric fields contributed by anisotropic band bendings are aligned between the doped p-type {100} facet with downward bending and the undoped n-type {110} facet with upward bending. Therefore, the directional migration of electrons to {100} facets is boosted by the intensified facet-oriented electric field and the photocatalytic performance is improved (2-fold) for hydrogen evolution with ∼1.75% AQY at 400 nm consequently.