N-doped carbon sheets supported P-Fe3O4-MoO2 for freshwater and seawater electrolysis

In Situ Fast Construction of Ni3S4/FeS Catalysts on 3D Foam Structure Achieving Stable Large-Current-Density Water Oxidation

By increasing the content of Ni3+, the catalytic activity of nickel-based catalysts for the oxygen evolution reaction (OER), which is still problematic with current synthesis routes, can be increased. Herein, a Ni3+-rich of Ni3S4/FeS on FeNi Foam (Ni3S4/FeS@FNF) via anodic electrodeposition to direct obtain high valence metal ions for OER catalyst is presented. XPS showed that the introduction of Fe not only further increased the Ni3+ concentration in Ni3S4/FeS to 95.02%, but also inhibited the dissolution of NiOOH by up to seven times. Furthermore, the OER kinetics is enhanced by the combination of the inner Ni3S4/FeS heterostructures and the electrochemically induced surface layers of oxides/hydroxides. Ni3S4/FeS@FNF shows the most excellent OER activity with a low Tafel slope of 11.2 mV dec-1 and overpotentials of 196 and 445 mV at current densities of 10 and 1400 mA cm-2, respectively. Furthermore, the Ni3S4/FeS@FNF catalyst can be operated stably at 1500 mA cm-2 for 200 h without significant performance degradation. In conclusion, this work has significantly increased the high activity Ni3+ content in nickel-based OER electrocatalysts through an anodic electrodeposition strategy. The preparation process is time-saving and mature, which is expected to be applied in large-scale industrialization.

Enhancing anti-chlorine corrosion of Ni3S2 by Mo-doping for mimic seawater electrolysis

Designing highly active electrocatalysts that can resist chloride ion (Cl-) corrosion during seawater electrolysis is still a challenge. Here, Mo-doping is introduced to synchronously improve the electrocatalytic activity and anti-chlorine corrosion of Ni3S2 toward the efficient overall seawater splitting. With commercial nickel-molybdenum foam (NMF) as the reactive substrates, Mo-doped Ni3S2 columnar arrays (Mo-Ni3S2/NMF) are fabricated via a one-step hydrothermal process, which expose abundant active sites with the ameliorated surface electronic configurations toward the enhanced binding with *OH (* denotes an active site) but the weakened one with *Cl. As expected, they afford the excellent bi-functionality for both oxygen and hydrogen evolution reactions (OER and HER), with the remarkably improved anti-corrosion to Cl- at anode as compared to pristine Ni3S2. In alkaline mimic seawater (1.0 M NaOH + 0.5 M NaCl), Mo-Ni3S2/NMF requires 330 mV (for OER) and 209 mV (for HER) overpotentials at the current density of ±100 mA cm-2, and a low cell voltage of 1.52 V at 10 mA cm-2 for overall seawater splitting. This work highlights a feasible strategy to explore highly active and stable electrocatalysts for sustainable H2 production.