Promising morphology of Poly‐2‐Mercaptoaniline/reduced graphene oxide nanosheets photocathode for green hydrogen generation from natural and artificial Red Sea water

A thin‐film photocathode composed of Poly(2‐mercaptoaniline)/Reduced Graphene Oxide Nanosheets (P2MA/rGO‐NS) was synthesized through a two‐step process involving the in situ chemical reduction of graphene oxide by the 2‐mercaptoaniline monomer, followed by oxidative polymerization to form the conducting polymer matrix. The resulting hybrid structure exhibits a compact and homogeneous morphology, where P2MA particles (~140 nm) are uniformly distributed within rGO sheets (~100 nm), facilitating efficient charge transport and interfacial contact. Optical analysis confirms broadband light absorption with an optical bandgap of ~2.4 eV, as suitable for visible‐light‐driven photoelectrochemical applications. The photocatalytic efficiency of the P2MA/rGO‐NS photocathode was assessed for hydrogen evolution using both natural Red Sea water and an equivalent synthetic seawater as electrolytes in a standard three‐electrode configuration. At −0.72 V, the photocurrent densities reached −0.7 and −0.5 mA/cm 2 for natural and artificial seawater, respectively, correlating with an average hydrogen evolution rate of 18 μA per 10 cm 2 per hour. The wavelength‐dependent photoresponse under monochromatic illumination demonstrated peak photocurrent densities of −0.63 and −0.57 mA/cm 2 at 340 and 440 nm, respectively, with a gradual decline to −0.54 mA/cm 2 at 730 nm, indicating broad‐spectrum responsiveness. The excellent photocatalytic performance, combined with stable operation under chopped illumination, low‐cost fabrication, and scalability, positions the P2MA/rGO‐NS photocathode as a strong candidate for sustainable hydrogen production from seawater in industrial‐scale application.