FCF-LDH/BiVO4 with synergistic effect of physical enrichment and chemical adsorption for efficient reduction of nitrate

Photoelectrochemical NO3− reduction (PEC NITRR) not only provides a promising solution for promoting the global nitrogen cycle, but also converts NO3− to the important chemicals (NH3). However, it is still a great challenge to prepare catalysts with excellent NO3− adsorption/activation capacity to achieve high NITRR. Herein, we designed a novel Fe2+Cu2+Fe3+LDH/BiVO4 (FCF-LDH/BVO) catalyst with synergistic effect of chemical adsorption and physical enrichment. Fe2+ in FCF-LDH/BVO provides the rich Lewis acid sites for the adsorption of NO3−, and the appropriate layer spacing of FCF-LDH further promotes the physical enrichment of NO3− in its interior, thus realizing the effective contact between NO3− and active sites (Fe2+). FCF-LDH/BVO showed excellent NH3 production performance (FENH3 = 66.1%, rNH3 = 13.8 μg h−1 cm−2) and selectivity (FENO2- = 2.5%, rNO2- = 4.9 μg h−1 cm−2) in 0.5 mol L−1 Na2SO4 electrolyte. In addition, FCF-LDH/BVO maintains the desirable PEC stability for six cycle experiments, showing great potential for practical application. The 14NO3− and 15NO3− isotope test provides strong evidence for further verification of the origin of N in the generated NH3. This LDH catalyst has a great potential in PEC removal of NO3− from groundwater. The dual effect of physical enrichment and chemical adsorption enables the promising PEC NITRR over FCF-LDH/BVO. Fe3+ and Cu2+ combined with H+ to form intermediates (Fe3+-H, Cu2+-H), which effectively hindered the HER competitive reaction and promoted the efficient PEC NITRR. [Display omitted] •The positive charges and large layer spacing of FCF-LDH enables the enrich of NO3−.•Lewis acid site (Fe2+) could selectively respond to Lewis base (NO3−).•Fe2+as an electron acceptor provides the required electrons for PEC NITRR.•Cu2+-H and Fe3+-H intermediates efficiently hinder the occurrence of HER.