An investigation of a putative photoreaction of dinitrogen with ferrofluid

Abstract

This work is an investigation of the putative photocatalytic reduction of N 2 to NH 3 in dilute aqueous ferrofluid, a recently reported reaction. We tested four different types of commercially available ferrofluid. Diluted ferrofluids were irradiated under nitrogen or argon, and the concentrations of ammonia , nitrate and nitrite in the reactor were measured at regular intervals. The substitution of argon for nitrogen produced no discernible difference in the experimental results. The possibility of the photocatalytic degradation of ammonia in aqueous solutions of ferrofluid was also investigated. In all of our experiments, variations in the measured concentrations of ammonia, nitrite and nitrate were small and random with respect to the irradiation time. There was no evidence that ammonia was either produced or degraded. Isotope-labeling experiments were performed, in which 15N 2 was irradiated in the presence of dilute ferrofluid. Small amounts of excess 15NH 3 (0.5–1.5 nmol) were measured in experimental samples and in control samples in which no nitrogen could have been fixed. The levels of 15NH 3 were too low to establish that any photocatalytic nitrogen reduction had occured, and were consistent with the hypothesis that no ammonia was produced.