Molecular Z-Scheme for Solar Fuel Production via Dual Photocatalytic Cycles

Abstract

Natural photosynthesis uses an array of molecular structures in a multiphoton Z-scheme for the conversion of light energy into chemical bonds (i.e., solar fuels). Here, we show that upon excitation of both a molecular photocatalyst (PC) and a substituted naphthol (ROH) in the presence of a sacrificial electron donor and proton source, we achieve photocatalytic synthesis of H2. Data support a multiphoton mechanism that is catalytic with respect to both PC and ROH. The use of a naphthol molecule as both a light absorber and H2 producing catalyst is a unique motif for Z-scheme systems. This molecular Z-scheme can drive a reaction that is uphill by 511 kJ mol–1 and circumvents the high-energy constraints associated with the reduction of weak acids in their ground state, thus offering a new paradigm for the production of solar fuels.

Metal–Organic Bichromophore Lowers the Upconversion Excitation Power Threshold and Promotes UV Photoreactions

“…Many different types of biphotonic processes have been uncovered, ,− among which sensitized triplet–triplet annihilation upconversion (sTTA-UC) is particularly promising. While upconversion has been intensively investigated from a photophysical perspective for applications in lighting and solar energy harvesting, − its use in photoredox catalysis is a relatively recent development. − Several non-catalytic photochemical reactions driven by upconversion have furthermore drawn interest. − …”

The confusion about S-scheme electron transfer: critical understanding and a new perspective

“…In nature, the photosynthesis of plants transfers energy through the Z-scheme. 36,37 Inspired by this idea, Bard designed the first generation of a Z-scheme photocatalytic system in 1979 and proposed to introduce suitable redox ion pairs to facilitate electron transfer between photocatalyst 1 (PS1) and photocatalyst 2 (PS2). 38 Although theoretically this liquid phase Z-scheme can facilitate carrier separation, many defects have been exposed in practical applications (Fig.…”

Combing Hollow Shell Structure and Z-Scheme Heterojunction Construction for Promoting CO2 Photoreduction

“…It is necessary to combine two or more optimization strategies in the photocatalytic process to maximize the photocatalytic efficiency. − Considering the multishelled hollow structure possessed light absorption promotion and rich active sites, ameliorating the charge separation of catalysts by other modifications may ultimately help improve the activity. Recently, a Z-scheme heterojunction has been proven to be an effective way to improve charge separation, in which the photogenerated electron of a semiconductor with low reduction potential recombines with the photogenerated holes on another semiconductor with low oxidation potential, reserving photogenerated electrons and holes with high redox abilities. − Furthermore, the multiple components of the Z-scheme heterojunction endows materials with multiple functions and more advantages, such as improved light absorption, spatially separated active sites, and even better stability if the corrosive photogenerated holes could be selectively consumed by photogenerated electrons. − Consequently, it is expected to achieve high CO 2 photoreduction performance by the construction of a Z-scheme heterojunction on multishelled hollow materials.…”