Solar Energy Storage in Polyoxometalate for On‐Demand Hydrogen Transportation and Evolution
Xiaoyu Dong, Xiao Fang, Bonan Li, Yu Feng, Yulu Liu, Lixin She, Xiangyu Meng, Yong Ding, Zhiming Zhang
Abstract
ABSTRACT Widespread application of solar‐driven hydrogen production is hindered by critical limitations: the inherent safety risks of high‐pressure H 2 storage/transport, and the intermittent nature of solar energy. To address these challenges, we develop a solar energy storage and on‐demand hydrogen production system by synergistically integrating commercial polyoxometalate (NH 4 ) 6 H 2 W 12 O 40 (W 12 ) with graphitic carbon nitride (g‐C 3 N 4 ). This system demonstrates remarkable efficiency in storing solar energy as electrons within W 12 during illumination. These stored electrons can be released on demand in the dark through Pt/C activation to produce H 2 , achieving a highly efficient hydrogen evolution rate of 3220 µmol g −1 h −1 under dark photocatalytic conditions. Notably, the system maintains robust performance under real‐world conditions, delivering an outdoor hydrogen evolution rate of 954 µmol g −1 h −1 under natural sunlight irradiation. Detailed analysis reveals an optimized electron storage‐release pathway, facilitated by the favorable alignment between the reduction potential of W 12 and the band structure of g‐C 3 N 4 , as well as the electrostatic self‐assembly driven by oppositely charged g‐C 3 N 4 and W 12 . In this system, solar energy is facilely stored as stabilized electrons within the POM‐semiconductor suspension, which can then be efficiently transported to light‐deficient environments and controllably released for on‐demand hydrogen evolution.