Enhanced Hydrogen Evolution under Simulated Sunlight from Neutral Electrolytes on (ZnSe)_0.85 (CuIn_0.7 Ga_0.3 Se₂ )_0.15 Photocathodes Prepared by a Bilayer Method

A (ZnSe)_0.85 (CuIn_0.7 Ga_0.3 Se₂ )_0.15 photocathode with a bilayer structure was fabricated and found to exhibit a photocurrent almost twice that of a photocathode with a monolayer structure during hydrogen evolution from water. The cathodic photocurrent reached maximum values of 12 and 4.9 mA cm^-2 at 0 and 0.6 V_RHE in a neutral phosphate buffer under simulated sunlight, while the half-cell solar-to-hydrogen conversion efficiency was 3.0 % at 0.6 V_RHE , with a maximum value of 3.6 % at 0.45 V_RHE . Cross-sectional mapping of the electron-beam-induced current established that the increased photocurrent can be attributed to improved uniformity at the solid-liquid junction in the bilayer sample, which results in enhanced carrier collection.