Superhydrophilic/superaerophobic amorphous Ni3S2/NiMoS electrocatalyst for enhanced hydrogen evolution

Ligand-Induced Electronic Structure Modulation of Self-Evolved Ni3S2 Nanosheets for the Electrocatalytic Oxygen Evolution Reaction

Modulating the electronic structure of the electrocatalyst plays a vital role in boosting the electrocatalytic performance of the oxygen evolution reaction (OER). In this work, we introduced a one-step solvothermal method to fabricate 1,1-ferrocene dicarboxylic acid (FcDA)-decorated self-evolved nickel sulfide (Ni3S2) nanosheet arrays on a nickel foam (NF) framework (denoted as FcDA-Ni3S2/NF). Benefiting from the interconnected ultrathin nanosheet architecture, ligand dopants induced and facilitated in situ structural reconstruction, and the FcDA-decorated Ni3S2 (FcDA-Ni3S2/NF) outperformed its singly doped and undoped counterparts in terms of OER activity. The optimized FcDA-Ni3S2/NF self-supported electrode presents a remarkably low overpotential of 268 mV to achieve a current density of 10 mA cm-2 for the OER and demonstrates robust electrochemical stability for 48 h in a 1.0 M KOH electrolyte. More importantly, in situ electrochemical Raman spectroscopy reveals the generation of catalytically active oxyhydroxide species (NiOOH) derived from the surface construction during the OER of pristine FcDA-Ni3S2/NF, contributing significantly to its superior electrocatalytic performance. This study concerns the modulation of electronic structure through ligand engineering and may provide profound insight into the design of cost-efficient OER electrocatalysts.

Enhancing Overall Water Splitting via Anion and Cation Synergistical Modulation in NiS Amorphous Compound

Designing and synthesizing cost-effective catalysts that exhibit excellent performance of both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is a formidable task in the field of electrocatalysis. Herein, we present a Fe- and P-codoped NiS amorphous film catalyst (FeNiSP) via meticulous control over the cations and anions of metal compounds. The doped Fe and P increases active sites, reduces charge transfer resistance, and modulates electronic structures of the NiS matrix. Leveraging these advantages, the FeNiSP showcases exceptional bifunctional activities of HER and OER, with remarkably low overpotentials of only 135 and 330 mV for achieving a current density of 100 mA·cm-2 during HER and OER, respectively. Additionally, a low cell voltage of 1.56 V at 10 mA·cm-2 was achieved when it was employed as both the anode and the cathode for water splitting. Finally, density function theory calculations further elucidate that the simultaneous presence of Fe and P in the NiS amorphous film catalyst leads to a decrease in the band center of S and Ni. This consequential effect maintains a balanced adsorption/desorption of protons and strengthened the adsorption of O-based intermediates on the surface of FeNiSP, subsequently contributing to the outstanding electrocatalytic HER and OER activities.