where nH2 is the amount of H2 formed (in mol), NA is the Avogadro's number (6.022×10 23 mol - 1 ), h is the Plank constant (6.626×10 -34 m 2 kg s -1 ), c is the velocity of light (3×10 8 m s -1 ) , t is the irradiation time (in s), I is the light intensity (in W m -2 ), λ is the wavelength (in m) and A is the irradiation area (in m 2 ).