Improving the photoelectrocatalytic activity of porous 2D-WO₃ nanosheets through Pt nanoparticle surface modification

The present work addresses the low separation efficiency of photo-generated charge carriers and their rapid recombination in tungsten oxide (WO₃) by introducing ultra-fine platinum surface modification of two-dimensional (2D) WO₃ nanosheets. The optimal concentration of Pt on 2D WO₃ is determined by controlling the concentration of the impregnating solution (c(H₂PtCl₆) = 1.0, 1.5, 2.0, 2.5, 3.0 mM), yielding the best photocatalytic degradation performance of the target pollutants and oxygen evolution of Pt-WO₃ with Pt NPs loading of about 7.2 wt%. High resolution transmission electron microscopy (HRTEM) shows Pt nanoparticles (NPs) with the size of around 2 nm uniformly distributed on the surface of the WO₃ nanosheet matrix. The presence of the Pt cocatalyst further promotes electron transfer and suppresses charge recombination, and by providing catalytic surface sites for the water oxidation reaction leads to increased O₂ evolution rates under light. Under visible light irradiation, the best photocatalytic degradation rate of Pt-WO₃ is 40 × 10^-4 min^-1 m^-2 g^-1, while the O₂ production rate is 61.4 μmol g^-1 h^-1, which are 5.0 and 6.2 times higher than those of the pristine WO₃ photocatalyst, respectively. Steady-state and transient fluorescence spectroscopy and photocurrent measurements indicate a lifetime of photogenerated electrons in Pt-WO₃ of 14.93 ns, which is longer than the 12.80 ns observed for pristine WO₃. Accordingly, the photocurrent density of Pt-WO₃ reaches 5.1 × 10^-2 mA cm^-2, which is significantly higher than the 2.0 × 10^-3 mA cm^-2 of pristine WO₃. This work provides a general method for optimizing the performance of WO₃ photocatalysts by benchmarking Pt-WO₃ as a reference for enhancing activity and overcoming the low separation efficiency of semiconductor oxide photocatalysts. Thus, this study provides experimental insights that can guide the rational design of advanced semiconductor-based photocatalysts.