Figure 3.

a) Stability tests of integrated PEC reactor under alternating 100 and 200 suns light flux using a Fresnel lens together with H₂ and O₂ production rates plotted as a function of time. The green shaded area shows the data when operating under 200 suns. The current density at 200 suns is 107.5 mA cm⁻². b) Depth profile of the Ni surface where the ⁹⁰NiO_x ⁻ secondary ion signal was monitored after the electrochemical oxidation reaction. Inset: the oxide layer thickness measured from the SIMS experiment plotted against electrochemical current density.