The STH efficiency of this system was calculated using Equation (1), where 𝑟 𝐻 2 is the rate of H2 evolution, ΔG 0 is the Gibbs energy change of the reaction (237 kJ mol -1 for liquid-phase and 228.6 kJ mol for vapour-phase overall water splitting under standard conditions at 298 K), Plight is the energy flux of the incident sunlight, and A is the device photoactive area (measured using ImageJ software as shown in Supplementary Fig. ). (1)