Enhanced hydrogen production from methanol–water solutions via photocatalysis using lead–cerium co-doped TiO2 with abundant oxygen vacancies

Abstract

Enhancing photocatalytic performance relies on efficient and stable solar energy utilization, broadening visible light absorption, and optimizing interfacial charge transfer mechanisms. We successfully synthesized lead–cerium co-doped TiO₂ enriched with oxygen vacancies (Ti^δ+–O_v(–Ce^δ+)–Pb²⁺) using sol–gel and direct addition methods. Results show that Pb²⁺ ions are uniformly distributed within the oxygen vacancy-rich TiO₂ lattice, synergizing with surface-embedded Ce²⁺/Ce³⁺ ions to extend the visible light absorption range of TiO₂. This led to a 32.3% increase in light absorption and an approximate 90% improvement in photoelectric conversion efficiency. The maximum photocurrent density reached 3.1 μA cm⁻², with a reduction of 0.15 eV in the initial oxidation potential and a 30% decrease in bandgap width. Under simulated sunlight (AM 1.5G), the hydrogen production rate of Ti^δ+–O_v(–Ce^δ+)–Pb²⁺ was 11.516 μmol h⁻¹ g⁻¹, double the combined output of TiO₂–Ce and TiO₂–Pb. Mechanistic analysis reveals that the superior performance stems from the interfacial sites in Ti^δ+–O_v(–Ce^δ+)–Pb²⁺, where the low-valent Pb²⁺ and variable-valent Ce³⁺/Ce⁴⁺ ions act as charge traps that promote efficient charge separation. Furthermore, surface-embedded Ce generates an uneven surface potential, facilitating the adsorption of formaldehyde molecules from the solution onto the modified TiO₂ surface and improving carrier dynamics. These findings provide new strategies for designing and optimizing high-efficiency photocatalytic materials.