A 3D-hierarchical flower like architecture of anion induced layered double hydroxides for competing anodic reactions

Abstract

The ongoing challenge in producing clean energy is to find highly active non-noble metal-based electrocatalysts. To overcome the high theoretical potential of the oxygen evolution reaction (OER, 1.23 V), alternative anodic reactions such as the urea oxidation reaction (UOR) may be considered to boost hydrogen generation. In this study, sulfur was incorporated into CoFeLDH to synthesize a S-CoFeLDH catalyst through the process of sulfurization, using Na₂S as the sulfur source. The catalyst showed an overpotential of 171 mV for the UOR and 268 mV for the OER, at a current density of 40 mA cm⁻². The catalyst also exhibited superior stability, with more than 100 hours of performance for both the OER and UOR at higher current densities. A full cell was constructed using a S-CoFeLDH||Pt/C electrode, which requires a potential of 1.52 V and 1.41 V for overall water and urea electrolysis, respectively. Density functional theory (DFT) was used to analyse the catalyst's activity and active sites by calculating its Gibbs free energy. The DFT results indicate that “Co” is the more prominent active site for the OER in S-CoFeLDH and the density of states (DOS) calculation predicts a favourable UOR.