Visible-light driven H2 evolution over a precious metal-free hybrid photocatalyst constructed from CuO and NiFe layered double hydroxide

Abstract

Composites of cupric oxide (CuO) and NiFe layered double hydroxide (NiFe-LDH) were prepared by three methods including hydrothermal (h) and solid-state reactions (s), as well as physical mixing (m). The photocatalytic H₂ generation of the composites and their calcined products (i.e., metal oxides) from a methanol aqueous solution was investigated under UV-visible light irradiation. The highest H₂ production was obtained for the mixed oxide catalyst (CuO/NiFe-MMO-h) with an apparent quantum yield of 0.42% at 400 nm, which was 2.7 times higher than that of the hydrothermally as-prepared one (CuO/NiFe-LDH-h). The close contact and strong interfacial interaction between the two components were achieved through the hydrothermal reaction, enabling efficient charge transport in the composite photocatalyst and subsequent H₂ evolution catalysis, which led to the enhanced photocatalytic activity. Density functional theory (DFT) calculations and an action spectrum analysis suggested that CuO acted as the active site, while the NiFe-hydroxide and derived NiFe-oxide generated the charge carriers upon photoexcitation with wavelength up to ∼600 nm.