Hierarchical TiO₂ nanowire/graphite fiber photoelectrocatalysis setup powered by a wind-driven nanogenerator: A highly efficient photoelectrocatalytic device entirely based on renewable energy

Photoelectrocatalysis is an efficient approach for the degradation of organic pollutants as well as for water splitting. However, an external power source supplying a direct current (DC) is essential to enhance the separation of photo-induced carriers. In this paper, a fully-functional photoelectrocatalysis device was constructed by connecting single crystalline TiO₂ nanowires assembled on graphite microfibers (TiO₂ nanowire/graphite fiber, TNGF) to a wind-driven triboelectric nanogenerator (WDTENG). The excellent photocatalytic and photoelectrocatalytic properties of TNGF originate from the ability of graphite fibers to transport rapidly the charge carriers, the high photocatalytic activity of TiO₂ nanowires and the photo-induced carrier separation enhancement created by the zero band gap of graphite. When this system is used for hydrogen generation via photoelectrocatalytic water splitting, the hydrogen evolution of the TNGF is significantly increased under assistance of the WDTENG. Photoelectrochemical analysis demonstrates that the separation and recombination of photo-induced charge carriers in the 7TNGF composite is dependent on the applied voltage bias. Thus, the wind driven generator provides large enough voltage bias for efficient charge separation, leading to a highly enhanced photocatalytic performance. This work is the first instance of high performance photoelectrocatalysis device aimed either at depollution or at hydrogen production which is entirely based on renewable energy.