Electroplating of surfactant-modified tin catalyst over a nickel foam electrode (Sn/Ni) for selective N2 yield from nitrate reduction as affected by Sn(200) and Sn(101) crystal facets

The crystal habit of metallic tin (Sn) on a nickel foam electrode (Sn/Ni) was manipulated by cationic surfactants in order to assess the selective conversion of NO3−. The Sn electroplating additive included benzethonium chloride (BZT), cetylpyridinium chloride (CPC), cetyltrimethylammonium chloride (CTAC), and hexyltrimethylammonium bromide (C6TAB). Characterization showed that FSn(200) (= Sn(200)/[Sn(200) + Sn(101)]), which indicated that the preference of the Sn(200) facet was modified by the surfactants. FSn(200) was in the following order: BZT > CPC > CTAC > C6TAB-Sn/Ni. As FSn(200) increased, a positive correlation between selectivity of N2 (SN2) and FSn(200) existed. The highest amount of SN2 (as high as 65 %) was obtained at FSn(200) = 0.95. The consecutive kinetics was derived to define the formation rate of the nitrogen compound in the constant current mode. NO3- and NO2- adsorption determined the effectiveness of nitrate reduction on the Sn(200) surface, which efficiently mediated H species formation.