Enabling Solar-Fuel Production with Biomimetic Architectures

Solar water oxidation has been considered a holy grail of scientists and engineers as it allows production and the use of valuable chemical compounds in a sustainable and carbon-neutral manner. In principle, virtually any kinds of chemical compounds can be produced by developing a proper electrocatalyst for synthesis of a target compound and coupling it with photocatalytic water oxidation, so-called artificial photosynthesis. Despite huge efforts made for decades, its practical application remains questionable due to its low efficiency and stability. Considering that it is enabled by a series of photoelectrochemical processes with multiple functional components, their tailored assembly into an integrated device with a nanoscale precision is critically required as well as development of individual components with high performance. Indeed, the Mother Nature has crafted a unique method to precisely assembly various functional components by self-assembly to effectively facilitate and couple individual processes/components. To date, however, the importance of the precise assembly has been often ignored, losing an opportunity to improve the performance of the photosynthetic devices even further. To address such a problem, we report herein the fabrication of biomimetic architectures, especially nacre-like layered structure and its application in efficient solar-fuel (e.g., H2) production. Briefly, we could readily deposit various functional components such as light-harvesting, charge transporting, and catalytic components using the layer-by-layer assembly in a desired order and dimension, resulting in the formation of precisely assembled nacre-like film with a significantly improved photocatalytic performances. This was because of efficient charge transport enabled by precise assembly of individual functional components, which is reminiscent of mesoscale organization of thylakoid organelles of plants. Our detailed analysis also revealed that the deposition of the nacrelike film allows engineering of the work-function of underlying electrodes, improving the performance of devices even further. Based on these findings, we could successfully build a bias-free photoelectrochemical cell for solar fuel production through the overall water splitting. We believe that our results demonstrate the versatility of biomimetic approaches for the design and fabrication of efficient photosynthetic devices