December 8, 2014

The ongoing worldwide effort to improve the efficiency of using solar energy to split water to produce hydrogen -electrolysis- has added a new milestone. Scientists from Ecole Polytechnique Federale de Lausanne (EPFL) in Switzerland have achieved a solar energy to hydrogen conversion efficiency of 12.3 percent using nickel and iron electrode catalysts and perovskite solar absorbers, all common materials.

Only once, in 1988, was the 10% conversion efficiency rate -considered exceptional- exceeded, and that system used expensive platinum electrodes. In addition to its lower cost, perovskite cells can generate higher average open circuit voltages than silicon cells. As a result, only two perovskite cells are needed to generate the required 1.7 V for water electrolysis. Silicon systems require three cells.

One drawback: perovskite PVs are unstable. Photocurrent degradation occurs in a matter of hours. While the cause is not yet fully understood, scientists hope to solve this problem soon to enable scaling up or production.