On-Demand Atomic Hydrogen Provision by Exposing Electron-Rich Cobalt Sites in an Open-Framework Structure toward Superior Electrocatalytic Nitrate Conversion to Dinitrogen

Abstract

Electrocatalytic nitrate (NO3 –) reduction to N2 via atomic hydrogen (H*) is a promising approach for advanced water treatment. However, the reduction rate and N2 selectivity are hindered by slow mass transfer and H* provision–utilization mismatch, respectively. Herein, we report an open-framework cathode bearing electron-rich Co sites with extraordinary H* provision performance, which was validated by electron spin resonance (ESR) and cyclic voltammetry (CV) tests. Benefiting from its abundant channels, NO3 – has a greater opportunity to be efficiently transferred to the vicinity of the Co active sites. Owing to the enhanced mass transfer and on-demand H* provision, the nitrate removal efficiency and N2 selectivity of the proposed cathode were 100 and 97.89%, respectively, superior to those of noble metal-based electrodes. In addition, in situ differential electrochemical mass spectrometry (DEMS) indicated that ultrafast *NO2 – to *NO reduction and highly selective *NO to *N2O or *N transformation played crucial roles during the NO3 – reduction process. Moreover, the proposed electrochemical system can achieve remarkable N2 selectivity without the additional Cl– supply, thus avoiding the formation of chlorinated byproducts, which are usually observed in conventional electrochemical nitrate reduction processes. Environmentally, energy conservation and negligible byproduct release ensure its practicability for use in nitrate remediation.

Iron‐Based Nanocatalysts for Electrochemical Nitrate Reduction

“…Xu et al published an article on an electron-rich Co-containing open-frame cathode for indirect electrochemical nitrate reduction mediated by atomic hydrogen (H*) with remarkable N 2 -selective supply, which gave us a new research idea. [139] The accumulation of electrons on Co sites increases the energy required to overcome the potential barrier to generate H 2 , which is beneficial for H* generation and stabilization. The H* generation rate can also be precisely matched by tuning the electronic structure of the Co site.…”

Defective Layered Double Hydroxide Nanosheet Boosts Electrocatalytic Hydrodechlorination Reaction on Supported Palladium Nanoparticles

“…% with the NO 3 – should be ascribed to that the NO 3 – will compete with the active sites and H* with 2,4-DCP. It is evidenced that as approximately 27% of NO 3 – is reduced to NH 3 during EHDC …”

“…− is reduced to NH 3 during EHDC. 41 Possible Origin of the Enhanced EHDC Performance. As observed in Figure 2c,d, the Pd/Ni x Al 100−x -LDH-OH v hybrid structure enables not only the formation of electrondefective Pd species (Pd δ+ ) but also the inclusion of OH v sites.…”

Diatomic Pd−Cu Metal‐Phosphorus Sites for Complete N≡N Bond Formation in Photoelectrochemical Nitrate Reduction

“…According to the previous analysis, the two reduction peaks correspond to the reduction of NO 3 À and NO 2 À , respectively. [24] The EIS Nyquist plots show that the…”