Solar hydrogen production: Splitting water with UV is now at almost 100% quantum efficiency

Water splitting using catalysts and sunlight, called photocatalysis has been a promising method of achieving solar hydrogen production for decades. However, most previous attempts only yielded an external quantum efficiency of less than about 50% representing the difficulty in efficient catalyst design for real world use. The catalyst needed to be designed better so every absorbed photon from the light source is used to make hydrogen. The key to improving efficiency was strategic placement of the co-catalysts and preventing defects in the semiconductor.

Published in the May 27th issue of Nature, Tsuyoshi Takata of Shinshu University et al. broke through new frontiers in power production by using aluminum-doped strontium titanate as a photocatalyst, whose properties have been extensively studied and therefore the best understood. They choose co-catalysts rhodium for hydrogen with chromium oxide, and cobalt-oxide for oxygen, by fine-tuning them to engage in only desired reactions. This method made possible for the reaction to have no recombination losses.

These new findings open the doors to achieve scalable and economically viable solar hydrogen production. Their design strategies succeeded in reducing defects that lead to near perfect efficiency, and knowledge obtained will be applied to other materials with intense visible light absorption. More work is still needed before we can run our cars on hydrogen, because this study focused on the use of ultraviolet light and abundant visible light from the sun remained unused. However, this great breakthrough has made that possibility no longer too good to be true, but in theory, just a matter of time. Hopefully it will encourage scientists, researchers and engineers to engage in this field, bringing the use of solar hydrogen power that much closer.