The construction of a dual direct Z-scheme NiAl LDH/g-C3N4/Ag3PO4 nanocomposite for enhanced photocatalytic oxygen and hydrogen evolution

Dual direct Z-scheme photocatalysts for overall water decomposition have demonstrated strong redox abilities and the efficient separation of photogenerated electron-hole pairs. Overall water splitting utilizing NiAl-LDH-based binary and ternary nanocomposites has been extensively investigated. The synthesized binary and ternary nanocomposites were characterized via XRD, FTIR, SEM, HRTEM, XPS, UV-DRS, and photoelectrochemical measurements. The surface wettability properties of the prepared nanocomposites were measured via contact angle measurements. The application of the NiAl-LDH/g-C3N4/Ag3PO4 ternary nanocomposite was investigated for photocatalytic overall water splitting under light irradiation. In this work, we found that in the presence of Ag3PO4, the evolution of H-2 and O-2 is high over LCN30, and 2.8- fold (O-2) and 1.4-fold (H-2) activity increases can be obtained compared with the use of LCN30 alone. It is proposed that Ag3PO4 is involved in the O-2 evolution reaction during water oxidation and g-C3N4 is involved in overall water splitting. Our work not only reports overall water splitting using NiAl-LDH-based nanocomposites but it also provides experimental evidence for understanding the possible reaction process and the mechanism of photocatalytic water splitting. Photoelectrochemical measurements confirmed the better H-2 and O-2 evolution abilities of NiAl-LDH/g-C3N4/Ag3PO4 in comparison with NiAl LDH, g-C3N4, Ag3PO4, and LCN30. The observed improvement in the gas evolution properties of NiAl LDH in the presence of Ag3PO4 is due to the formation of a dual direct Z-scheme, which allows for the easier and faster separation of charge carriers. More importantly, the LCNAP5 heterostructure shows high levels of H-2 and O-2 evolution, which are significantly enhanced compared with LCN30 and pure NiAl LDH.