Carbon dots enhance photoelectrochemical water splitting activity of SrTiO3 nanoparticles: Band tuning and excellent charge separation

Abstract

The photoelectrochemical (PEC) activity of Strontium titanate (SrTiO₃) is constrained by its insufficient light absorption and significant carrier recombination. In this study, carbon dots (CDs) are integrated as co-catalysts onto the surface of oxygen-vacancy-doped mesoporous spherical SrTiO₃ nanoparticles to address these limitations and enhance PEC activity. Experimental characterizations and DFT calculations elucidate that the CDs demonstrated significant synergistic enhancements in PEC performance, particularly in band alignment, visible light absorption, and charge carrier transport, which collectively accelerated surface catalytic reactions. Most importantly, the electronic structure of SrTiO₃ was optimized by CDs, and their interfacial interaction plays an important role in enhancing its PEC performance. As a result, the optimal 0.005 %CDs/Sr_XTiO_3-δ photoanode achieves a photocurrent density of 1.37 mA/cm² at 1.23 V vs. RHE, significantly surpassing that of Sr_XTiO_3-δ (0.73 mA/cm²) and pristine SrTiO₃ (0.109 mA/cm²). Additionally, the incident photon-to-current conversion efficiency (IPCE) reaches 34 % for 0.005 %CDs/Sr_XTiO_3-δ, compared to 18.2 % for Sr_XTiO_3-δ and 2.6 % for SrTiO₃. These findings present a straightforward and effective method for designing high-performance catalysts for PEC water splitting.