Electrocatalytic upcycling of nitrate and hydrogen sulfide via a nitrogen-doped carbon nanotubes encapsulated iron carbide electrode

To achieve the efficient electrocatalytic upgrading of nitrate (NO3-) and hydrogen sulfide (H2S) to value-added ammonia (NH3) and sulfur (S) from wastewater, herein, we report a remarkable nitrogen-doped carbon nano tubes encapsulated iron carbide array electrode (Fe3C@N-CNTs/IF) as both cathode and anode for the efficient electrocatalytic reduction of NO3- to NH3 and oxidation of H2SS to S, respectively. Both experimental and theoretical calculation confirm the high activity of Fe3C@N-CNTs/IF. A maximal NH3 faradaic efficiency of similar to 97.9% with the yield rate of 0.922 mg h(-1) cm(-2) at 1.1 V vs. SCE and the S yield rate of 33.76 mg h(-1) cm(-2) at the current density of 100 mA cm(-2) can be achieved. In addition, a flow cell is employed with a multifunctional Fe3C@N-CNTs/IF electrode with channels made by laser to maintains excellent stability for continuous upcycling NO3- and H2S to produce NH3 and S, which demonstrates its massive potential for practical application.

Automated summary

In this study, a highly efficient electrocatalytic method for upgrading nitrate and hydrogen sulfide to ammonia and sulfur in wastewater was reported. The nitrogen-doped carbon nanotubes encapsulated iron carbide array electrode showed high catalytic activity and excellent yield rates for both ammonia and sulfur. The electrode also demonstrated great stability for practical application.