Enhancing Hydrogen Diffusion in Catalytic Removal of Nitrate Using a Flow Reactor

The excessive application of nitrogen fertilizers, pesticides and sewage irrigation in agriculture has caused serious nitrate pollution in natural water systems. Selective catalytic reduction of nitrate (NO 3 − ) with hydrogen (H 2 ) to dinitrogen (N 2 ) is a promising approach to address this public health risk, but the practical application of this denitrification technology is currently limited by the low NO 3 − removal rate and the high cost of palladium-based catalysts. In this work, we report an integrated thermo/electro-catalytic flow reactor for nitrate reduction. The innovative design of the solid–gas–liquid triple-phase interface enables high-throughput catalytic reduction of NO 3 − to N 2 . H 2 can be either supplied to the flow cell from an external source or produced in situ via the integrated water electrolyzer unit. The H 2 utilization efficiency of the reported flow reactor is increased significantly over what observed in conventional batch reactors. Moreover, a surface Pd enriched Cu@Pd catalyst was synthesized by galvanic replacement to boost Pd utilization. The Cu@Pd catalyst showed an unprecedented specific NO 3 − removal rate of ∼ 15.5 mM_NO_3^ - g_Pd^ - 1 min^ - 1 . Graphical Abstract