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The PEC cell, like that of a leaf, includes a light-collection mechanism and a mechanism for separating electric charges and delivering them to the active sites where the chemical reactions occur. In PEC cells, however, the reactions take place in ways that differ significantly from the process in nature, using simpler catalytic molecules. Nanophotovoltaics (nanoPVs) collect light and separate electric charge. A major project of the subtask explores new nanoscale photovoltaic elements that will serve as building blocks for the macroscale PV arrays needed in the development of nanomaterial-based PEC cells. A focus on nanoscale objects allows us to design and control the structure of the PV element at the atomic level, and develop mixtures of metals with characteristics such as band gaps and band edges that can only be obtained in nanometer-sized particles. Furthermore, at this scale, morphologies of PV elements can be exploited that afford simultaneous optimization of visible light absorption and charge-transport properties.

The nanoPV project is made up of three different subprojects, each consisting of three to six graduate students and postdoctoral fellows supervised by two or three Principal Investigators. These teams are the operational units of the Center. Each subproject addresses one or more specific scientific challenges associated with nanoPVs. They include new inorganic semiconductor materials based on 1-D nanorod and nanotube designs, capped by metal oxide layers, with the goal of overcoming the problem of the photochemical degradation that takes place when they are exposed to water; and the exploitation of nanorod/nanodot designs for achieving high-efficiency light absorption, charge separation, and collection. Another subproject team is exploring hybrid systems consisting of an organic polymeric light absorber bonded with atomic precision to metal contacts.

Catalysts play a critical role. Catalysts are the focus of another project in the subtask. The lack of effective catalysts is among the most serious obstacles preventing the development of an efficient and scalable artificial fuel generator, and a relatively large fraction of SERC resources is committed to developing them. For each type of reaction—proton reduction, carbon dioxide reduction, and water oxidation—a subproject team is exploring ways of utilizing abundant metals to make robust