Electrocatalytic hydrodechlorination on Pd, utilizing the H + of H 2 O as hydrogen sources, represents a promising technology to detoxify the chlorinated organic pollutants (COPs) in water bodies. However, Pd alone affords limited activity due to its low efficacy in H 2 O disassociation and the poor mass diffusion of COPs that are commonly of low concentrations in the environment. Herein, we demonstrate that arming Pd with OH − vacancy-bearing NiAl-layered double hydroxide nanosheets (Pd/ Ni x Al 100−x -LDH-OH v ) can significantly improve its performance, benefiting from the enhanced H 2 O disassociation at OH v and the facilitated C−Cl cleavage on the supported Pd nanoparticles. Al 3+ is also indispensable because it promotes the formation and regeneration of OH v , but an overload will reduce the number of accessible OH v and weaken its function. Pd/Ni 67 Al 33 -LDH-OH v with the optimal Ni/Al ratio delivers a peak specific activity of 0.53 min −1 m −2 and mass activity of 6.54 min −1 g −1 Pd in treating 50.0 mg L −1 2,4-dichlorophenol (2,4-DCP, a probe COP) at −0.25 V versus RHE, outperforming most of the reported catalysts. To address the mass diffusion issue, Pd/Ni 67 Al 33 -LDH-OH v is integrated into a customized continuous-flow membrane cell. When fed a dilute wastewater (20.4 mg L −1 ), the system affords a 2,4-DCP removal rate of 3.75 g 2,4-DCP g catalyst −1 h −1 and faradaic current efficiency of 42.6%, which is 3.2 and 4.0 times that obtained in a traditional batch reaction system, respectively.

No abstract

Electrocatalytic reduction of nitrate to NH 3 (NO3RR) on Cu offers sustainable NH 3 production and nitrogen recycling from nitrate-contaminated water. However, Cu affords limited NO3RR activity owing to its unfavorable electronic state and the slow proton transfer on its surface, especially in neutral/alkaline media. Furthermore, although a synchronous "NO3RR and NH 3 collection" system has been developed for nitrogen recycling from nitrate-laden water, no system is designed for natural water that generally contains low-concentration nitrate. Herein, we demonstrate that depositing Cu nanoparticles on a TiO 2 support enables the formation of electron-deficient Cu δ+ species (0 < δ ≤ 2), which are more active than Cu 0 in NO3RR. Furthermore, TiO 2 −Cu coupling induces local electric-field enhancement that intensifies water adsorption/ dissociation at the interface, accelerating proton transfer for NO3RR on Cu. With the dual enhancements, TiO 2 −Cu delivers an NH 3 -N selectivity of 90.5%, mass activity of 41.4 mg-N h g Cu −1 , specific activity of 377.8 mg-N h −1 m −2 , and minimal Cu leaching (<25.4 μg L −1 ) when treating 22.5 mg L −1 of NO 3 − -N at −0.40 V, outperforming most of the reported Cu-based catalysts. A sequential NO3RR and NH 3 collection system based on TiO 2 −Cu was then proposed, which could recycle nitrogen from nitratecontaminated water under a wide concentration window of 22.5−112.5 mg L −1 at a rate of 209−630 mg N m −2 h −1 . We also demonstrated this system could collect 83.9% of nitrogen from NO 3 − -N (19.3 mg L −1 ) in natural lake water.

No abstract