Leaf-inspired highly efficient and stable photocatalyst for $CO_2$ conversion

Abstract

A leaf adopts to natural photosynthesis based on the unique structural and chemical strategies. Structurally, sponge cells in the leaf trigger light scattering and offer efficient gas diffusion and adsorp-tion pathway. Chemically, leaf’s unique catalytic system, so called a Z-scheme, could generate photoex-cited electrons at one chlorophyll (P680) and transport them via electron transfer channel (Cytochrome $b_6f$ complex) to the other chlorophyll (P700) in order to increase product yield and selectivity. Here, we created a leaf-inspired highly stable metal-free photocatalyst, consisting of few layered molybdenum disulfide ($MoS_2$) and mesoporous titanium dioxide ($TiO_2$) on graphene aerogel. Similar to the sponge cells, graphene aerogel structures and mesoporous $TiO_2$ nanoparticles imitate hierarchical architecture of a leaf to increase mass transportation and light absorption. Also, the artificial Z-scheme is construct-ed by precisely controlled energy pathway from $TiO_2$ via graphene to few layered $MoS_2$, which improve charge transfer, redox power of carriers, and broad light absorption range. The resulting artificial leaf photocatalyst shows robust stability and outstanding photocatalytic activity ($92.33 \mu mol CO /g \cdot h$) ca. 15 times higher than bare $TiO_2$, which highly efficient performances than those of metal-based catalysts.