Fig. 4
Electrochemical durability of surface-tailored GaInP2 photocathodes performing the HER under bias. Current density–time (J–t) plots of GaInP2 photocathodes in an acidic electrolyte (0.5 M H2SO4) for a short-term and b long-term measurements, at various materials configurations including bare GaInP2 (black data), bare GaInP2 deposited with MoS2 (yet without (NH4)2S-treatment, red data), nanostructured GaInP2 with (NH4)2S-treatment (yet without MoS2-deposition, blue data), and nanostructured GaInP2 with MoS2 (yet without (NH4)2S treatment, green data), measured at an electrode potential of 0 V (vs. RHE) under simulated AM1.5 G solar illumination. Dry etching and (NH4)2S-treatment were performed for 4 min and 15 min, respectively. c Top-view SEM images of bare and nanostructured/(NH4)2S-treated GaInP2 (scale bar: 500 nm) before and after the stability test in b (i.e., ~1 h for bare, ~124 h for NS). d Reflectance spectra of nanostructured and (NH4)2S-treated GaInP2 photocathodes before and after the stability test in b. Insets show corresponding photographic images of samples (scale bar: 5 mm). e XPS spectra of bare GaInP2 before and after the (NH4)2S-treatment. f J-t plots of bare and nanostructured GaInP2 photocathodes with and without (NH4)2S-treatment, obtained under the same measurement condition as in a
