Laser-Regulated CoFeRu-LDH Nanostructures: Nitrite-to-Ammonia Production in Zn-Nitrite Battery and Oxygen Evolution in Water Electrolysis

Abstract

Herein, the design and synthesis of Ru-doped CoFe-layered double hydroxide (CoFeRu & horbar;LDH) nanostructures is presented via an innovative yet straightforward pulsed laser method. The CoFeRu & horbar;LDH catalyst demonstrates outstanding electrocatalytic performance, achieving a high NH4+ Faradaic efficiency (FE) of 89.65% at -0.7 V versus reversible hydrogen electrode for nitrite reduction reaction (NO2-RR) and a low overpotential of 297 mV at 10 mA cm-2 for oxygen evolution reaction (OER). Comprehensive in situ and ex situ analyses reveal the electrochemically energetic species formed on the CoFeRu & horbar;LDH surface during the NO2-RR and OER. Theoretical studies confirm that Ru doping plays an imperative role in tuning the electronic structure of CoFeRu & horbar;LDH, lowering its reaction barriers, and thereby remarkably enhancing its NO2-RR and OER performance. Specifically, a galvanic Zn-nitrite battery using CoFeRu & horbar;LDH as the cathode efficiently converts NO2- to NH4+ with an FE of 96.8% while concurrently generating electricity with a power density of 4.14 mV cm-2. Furthermore, pairing CoFeRu & horbar;LDH as the anode with Pt/C as the cathode in water electrolysis enables H2 production at a low cell voltage of 1.57 V at 10 mA cm-2. This study presents a new pathway to designing versatile, high-performance electrocatalysts for sustainable energy conversion and the production of carbon-free NH3 and H2 fuels.