Water collection from air by ionic liquids for efficient visible-light-driven hydrogen evolution by metal-free conjugated polymer photocatalysts

The scarcity of Groundwater on Earth increases the necessity to make full use of the ubiquitous atmospheric water (H2O). Photocatalytic conversion of the H2O from the air to hydrogen (H2) under visible-light irradiation by metal-free conjugated polymer photocatalysts (CMPs) would be an interesting and challenging route for fully utilizing H2O resources and converting to sustainable and green energy. However, there is no such strategy reported up to now, to the best of our knowledge. Here, for the first time, we used various CMPs for H2 production using captured moisture by ionic liquids (ILs) under visible-light irradiation. The presence of ILs in the H2O-absobed H2O/ILs mixtures could enhance photocatalytic H2 evolution rate when compared to the pure H2O. Particularly, the accelerated effect of [BMIM][BF4] was the highest (29-fold), with the highest H2 production rate of 96.5 μmol g−1 h−1 among all the IL-related systems investigated. We attributed the high efficiency of H2 photo-evolution from atmospheric H2O to the activation of H2O by ILs and the highly dispersion of photocatalysts in H2O/ILs system. This work might open a new field to convert sustainable and ubiquitous atmospheric H2O resources to clean H2 fuels.