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.

中文翻译：

---

水作为甲酸光催化制氢的助催化剂

摘要 H2O 对光催化甲酸（FA）脱氢的催化作用越来越受到关注，但详细的机理研究仍处于起步阶段。在这里，我们从理论和实验两个方面深入系统地探索了 H2O 用于光催化 FA 脱氢的催化过程。具体而言，通过在室温和大气压下简单地添加适当的 H2O，我们证明了与各种光催化剂系统相比，光催化制氢的效率提高了 2~4 倍。理论和实验结果表明，H2O 的加入可以明显降低 FA 脱氢的活化能，因为来自 H2O 的 OH*（活化的 OH-）和 H*（活化的 H+）可以通过氢键协助 FA 的 OH 断裂，并通过与来自 FA 的 H* 偶联促进 H2 的产生。反应后 H2O 仍保持原来的状态。同时，通过引入不同的助催化剂，如用于 CdS 系统的 CoP、Pt、Pd、Ru、Au，以及 TiO2 和 C3N4 的不同半导体，我们证明了促进 H2 产生的 H2O 可以被视为光催化 FA 脱氢反应的一般策略. 该结果为H2O在催化领域的催化作用提供了重要启示。以及 TiO2 和 C3N4 的不同半导体，我们证明了促进 H2 产生的 H2O 可以被视为光催化 FA 脱氢反应的一般策略。该结果为H2O在催化领域的催化作用提供了重要启示。以及 TiO2 和 C3N4 的不同半导体，我们证明了促进 H2 产生的 H2O 可以被视为光催化 FA 脱氢反应的一般策略。该结果为H2O在催化领域的催化作用提供了重要启示。