Water as a cocatalyst for photocatalytic H2 production from formic acid

Abstract The catalytic role of H2O for photocatalytic formic acid (FA) dehydrogenation has received increasing interest, however, the detailed mechanism investigation still in infancy. Here, we deeply and systematically explore the catalytic process of H2O for photocatalytic FA dehydrogenation form both theoretical and experimental aspects. Specifically, we certified a 2∼4-fold efficiency increase in the photocatalytic H2 production over various photocatalysts systems by simply adding appropriate H2O at room temperature and atmosphere pressure. Theoretical and experimental results reveal that the addition of H2O could apparently decrease the activation energy of FA dehydrogenation, since the OH* (activated OH−) and H* (activated H+) from H2O could assist the O H scission of FA through hydrogen bonding and promote H2 production though coupling with the H* from FA, respectively. The H2O still maintains at the original state after the reaction. Meanwhile, by introducing different cocatalysts, such as CoP, Pt, Pd, Ru, Au for CdS systems, and different semiconductors of TiO2 and C3N4, we demonstrated that H2O promotion for H2 production can be regarded as a general strategy for photocatalytic FA dehydrogenation reaction. The results provide significant inspiration for the catalytic role of H2O in the catalysis field.