A Monolithic Artificial Leaf for Solar Methanol Production from CO₂ and H₂O

Methanol, an important liquid fuel and chemical feedstock, has yet to be produced using solar energy, H₂O, and CO₂ as sole inputs in a standalone device. This study directly addresses this longstanding challenge through presenting the first demonstration of unbiased solar methanol production from CO₂ and H₂O with a monolithic artificial leaf design, surpassing the previous best energy efficiency in solar alcohol production by at least 1 order of magnitude. We first develop a new generation of photocathodes based on Si micropillar arrays and a cobalt tetraaminophthalocyanine molecular catalyst. By integrating a C₆₀ interlayer that facilitates unidirectional electron transfer through the semiconductor/catalyst interface, we realize a photovoltage of 500 mV, one of the highest recorded for single-junction Si-based photoelectrodes in aqueous CO₂ reduction, as well as unprecedented methanol formation with a Faradaic efficiency of 30% and a partial current density of 6.3 mA cm^-2. We further integrate the photocathode with a multijunction perovskite photovoltaic minimodule to afford a standalone solar fuel system, which demonstrates a light-to-methanol conversion efficiency of 0.8%, 32 times higher than the present record in light-to-alcohol conversion with an artificial leaf.