Solution Plasma Processing Single-Atom Au₁ on CeO₂ Nanosheet for Low Temperature Photo-Enhanced Mars–van Krevelen CO Oxidation

Creating oxygen vacancies in metal oxide support holds promise in anchoring and stabilizing single atom metals, activating the lattice oxygen of metal oxide and accelerating Mars–van Krevelen (MvK) catalytic oxidation. However, it is challenging to achieve nearly 100% trapping of single atom metal in solution by oxygen vacancy typed metal oxide, resulting from the difficulty in synchronized formation of oxygen vacancies and capture of the single atom metal. In this study, a solution plasma process (SPP) is developed, enabling ≈99% trapping of single atom Au by using oxygen vacancy typed CeO₂ nanosheet in 2 min. Owing to the large number of electrons and free radicals present in the plasma region, the SPP can simultaneously reduce HAuCl₄ to single-atom Au and bring oxygen vacancies as anchoring sites onto CeO₂. The catalytic test of CO oxidation assisted by solar light can reach a conversion of 91.7% with a high turnover frequency of 1.3 s⁻¹ at room temperature, far exceeding the requirements for the “150 °C challenge.” A photo-enhanced MvK pathway is proposed for the superior performance of Au₁/CeO₂. This study not only explores a novel solution approach to prepare single-atom metal catalysts, but also provides an effective strategy for efficient low-temperature catalytic oxidation.