Variable valence Mo5+/Mo6+ ionic bridge in hollow spherical g-C3N4/Bi2MoO6 catalysts for promoting selective visible light-driven CO2 photoreduction into CO

Herein, the catalysts of ultrathin g-C3N4 surface-modified hollow spherical Bi2MoO6 (g-C3N4/Bi2MoO6, abbreviated as CN/BMO) were fabricated by the co-solvothermal method. The variable valence Mo5+/Mo6+ ionic bridge in CN/BMO catalysts can boost the rapid transfer of photogenerated electrons from Bi2MoO6 to g-C3N4. And the synergy effect of g-C3N4 and Bi2MoO6 components remarkably enhance CO2 adsorption capability. CN/BMO-2 catalyst has the best performances for visible light-driven CO2 reduction compared with single Bi2MoO6 and g-C3N4, i.e., its amount and selectivity of CO product are 139.50 μmol g−1 and 96.88% for 9 h, respectively. Based on the results of characterizations and density functional theory calculation, the photocatalytic mechanism for CO2 reduction is proposed. The high-efficient separation efficiency of photogenerated electron-hole pairs, induced by variable valence Mo5+/Mo6+ ionic bridge, can boost the rate-limiting steps (COOH*-to-CO* and CO* desorption) of selective visible light-driven CO2 conversion into CO. It inspires the establishment of efficient photocatalysts for CO2 conversion.