Robust catalysts for solar-driven water splitting

Abstract

The efficient generation of mol. hydrogen from sunlight and water is one of the holy grails of 21st century chem. Hydrogen is a clean, renewable fuel that could play a key role in meeting the world's skyrocketing demand for energy. Several investigators have employed hydrogenases as catalysts coupled to cathodes for H_2 prodn., as these enzymes can operate in water with very high turnover frequencies. But these enzymes are not stable under aerobic conditions, so recent work has largely focused on robust inorg. materials. Among inorg. materials, platinum is a very active catalyst for proton redn., but scarcity and high cost limit its widespread use. Clearly, we must replace platinum in solar-driven water splitting devices!. The good news is that investigators in the NSF CCI Solar Fuels Program have accepted this challenge: working together, we have found that Ni-Mo nanopowders and metal phosphide nanocrystals have catalytic efficiencies near that of platinum for hydrogen evolution from water. We also have developed robust mixed-metal nanostructured catalysts for the prodn. of oxygen from water. There is an urgent need to find even better water oxidn. catalysts, as the protons and electrons liberated when oxygen is evolved are the fundamental particles required for sustainable energy storing reactions, not only for hydrogen prodn., but also for the conversion of nitrogen and carbon dioxide to fuels and chems.