Synergy of Surface Phosphates and Oxygen Vacancies Enables Efficient Photocatalytic Methane Conversion at Room Temperature

Room-temperature photocatalytic conversion of CH4 intoliquid oxygenates with O-2/H2O provides an appealingroute for sustainable chemical industry, which, however, suffers frompoor efficiency due to the undesired carrier kinetics and low yieldof reactive oxygen species of the currently available photocatalysts.Here, we report an effective surface engineering strategy where concurrentconstructions of oxygen vacancies and phosphate sites on TiO2 nanosheets address the above challenge. The surface oxygen vacanciesand phosphates are respective acceptors of photogenerated electronsand holes for promoted separation and migration of charge carriers.Moreover, in addition to the facilitated activation of O-2 to (OH)-O-& BULL; by electrons at oxygen vacancies, the surfacephosphates also facilely adsorb H2O via hydrogen bondsand thus effectively transfer holes to H2O for enhanced (OH)-O-& BULL; production, thereby boosting CH4 conversion.As a result, compared with TiO2 sheets with only oxygenvacancies, a 2.8 times improvement in liquid oxygenate productionwith near-unity selectivity is achieved by virtue of the synergy ofsurface oxygen vacancies and phosphate sites, together with an unprecedentquantum efficiency of 19.8% under 365 nm irradiation.

Automated summary

We report an effective surface engineering strategy for TiO2 nanosheets, where concurrent constructions of oxygen vacancies and phosphate sites address the poor efficiency problem in the photocatalytic conversion of CH4 into liquid oxygenates. The surface oxygen vacancies and phosphates play roles as acceptors of photogenerated electrons and holes, promoting the separation and migration of charge carriers. In addition to activating O2 to (OH)-O- by electrons at oxygen vacancies, the surface phosphates effectively adsorb H2O via hydrogen bonds, facilitating the transfer of holes to H2O for enhanced (OH)-O- production and boosting CH4 conversion.