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.