Facile, Controllable, and Ultrathin NiFe-LDH In Situ Grown on a Ni Foam by Ultrasonic Self-Etching for Highly Efficient Urine Conversion

As the primary source of nitrogen pollutants in domestic sewage, urine is also an alternative for H2 production via electrochemical processes. However, it suffers from sluggish kinetics and noble-metal catalyst requirement. Here, we report a non-precious ultrathin NiFe-layered double hydroxide catalyst for the remarkable conversion of urea into N2 and H2 , which is in situ grown on a Ni foam via ultrasonic self-etching in Fe3+/ethylene glycol (EG). EG regulates the etching rate of Fe3+ , resulting in an ultrathin nanosheet structure with the aid of ultrasonication. This structure dramatically promotes the dehydrogenation process via decreasing the nanolayer thickness from 120 to 3.4 nm and leads to a 4.8-fold increase in the generation of active sites. It exhibits record urea oxidation kinetics (390.8 mAmiddotcm(-2) at 1.5 V vs RHE) with excellent stability (120 h), which is 11.8 times better than that of commercial Pt/C catalyst (33.1 mAmiddotcm(-2)). Tests with real urine at 20 mA cm(-2) achieve 74% total nitrogen removal and 2853 mu molmiddoth(-1) of H-2 production. This study provides an attractive landscape for producing H-2 by consuming urine biowastes.

Automated summary

This study introduces a non-precious ultrathin NiFe-layered double hydroxide catalyst for efficient conversion of urea into N2 and H2. The catalyst exhibits ultrathin nanosheet structure that promotes dehydrogenation process and shows excellent stability. This research provides a promising approach for H2 production from urine biowastes.