Hydrogen production by photocatalysis using formic acid and black sand

Abstract Photocatalytic properties of the magnetic fraction (MF) from a black sand sample, were evaluated to produce hydrogen by heterogeneous photocatalysis, using formic acid as hole scavenger. MF is mainly composed of ilmenite (FeTiO 3 ), hematite (α-Fe 2 O 3 ), maghemite (γ-Fe 2 O 3 ), and magnesioferrite (MgFe 2 O 4 ), as detected by X-ray analysis. MF particles are rugose with irregular morphology, smooth surface (without porous), and coarse surface. Also, Energy Dispersive X-ray Spectroscopy (EDS) microanalysis indicated the presence of major elements such as Fe, Ti, Si, Al, Mg, Ni, Cr, Ca, Na, K. MF sample absorbed from 200 to 2,500 nm wavelengths with several absorption edge energies due to indirect transitions and interactions, probably of FeTiO 3 and its interaction with the other semiconductors. The value obtained for the main absorption edge for Band gap (indirect transitions) of the MF was 3.5 eV. An experimental design (2 k ) was carried out to examine the influence of the initial concentration of formic acid (1–20 v/v %), the photocatalyst dose (0.1–1 g/L), and reaction time (2–8 h) on the amount of produced hydrogen and the residual Total Organic Carbon (TOC) content in the liquid phase. The greatest hydrogen production (150.97 μmol/L) was obtained using 20 % v/v formic acid and 1 g/L of photocatalyst after 8 h of irradiation.