Protective Cerium Oxide Coating Promoted Ce‐Doping and Reconstruction of High‐Valence NiFe Sulfide toward Robust Overall Water Splitting

Abstract

Active and stable electrocatalysts toward oxygen evolution reaction (OER) are essential for alkaline water splitting. Herein, an efficient and durable high‐valence NiFe‐based OER electrocatalyst is developed, featuring a protective CeO2−x coating to prevent the corrosion of carbon substrates during oxidative OER operation, ensuring excellent catalyst stability. The incorporation of a CeO2−x coating also leads to the formation of a Ce‐doped NiFe sulfide catalyst. The Ce modulator enables the dynamic transformation of NiFe sulfide into highly active (oxy)hydroxide species with high‐valence Ni sites and enhanced Ni─O covalency, thereby improving its OER catalytic activity. Accordingly, the prepared NiFeS2/CeO2−x/CC catalyst achieves enhanced OER activity with an overpotential of 260 mV at 100 mA cm−2 in 1.0 m KOH. Moreover, the catalyst achieves 100 mA cm−2 current density at an overpotential of 187 mV for the hydrogen evolution reaction. The anion exchange membrane water electrolyzer reached 500 mA cm−2 at 1.73 V cell voltage with excellent stability for 500 h continuous operation. This study demonstrates a promising approach for the fabrication of robust water‐splitting electrocatalysts.

Real Active Site Identification of Co/Co3O4 Anchoring Ni-MOF Nanosheets with Fast OER Kinetics for Overall Water Splitting

“…45 Considering the dual effect of Co doping and Co 46 The symmetrically filled electronic degenerate orbitals (e g and t 2g ) of Ni 2+ prevent Jahn−Teller (JT) distortion, requiring a high input energy for the OER to proceed. 47 In contrast, the electronic valence configuration of Co 2+ is 3d 7 with the high-spin state, leading to unpaired electrons in the πsymmetric (t 2g ) d-orbitals that interact with the bridging O 2− through π-donation. 48 50,51 The OER activity of the variously prepared catalysts was assessed by a three-electrode measurement system in 1.0 M KOH, and all linear sweep voltammetry (LSV) curves were calibrated with 95% iR compensation.…”

“…In Ni NDC/CP, the π-symmetry d -orbitals ( t 2g ) of the Ni 2+ are fully occupied, resulting in the e – –e – repulsion as the main interplay of the bridging O 2– and Ni 2+ . The symmetrically filled electronic degenerate orbitals ( e g and t 2g ) of Ni 2+ prevent Jahn–Teller (JT) distortion, requiring a high input energy for the OER to proceed . In contrast, the electronic valence configuration of Co 2+ is 3d 7 with the high-spin state, leading to unpaired electrons in the π-symmetric ( t 2g ) d-orbitals that interact with the bridging O 2– through π-donation .…”

Constructing Amorphous‐Crystalline Interfacial Bifunctional Site Island‐Sea Synergy by Morphology Engineering Boosts Alkaline Seawater Hydrogen Evolution

“…Furthermore, the analysis of the Electron Localization Function (ELF) provides additional support for the stability of PdCo-Co 3 S 4 , offering insights into the material bonding characteristics. [33] The ELF value between Co and Pd atoms is ≈0.05, indicating a metallic bond characteristic in Co─Pd interactions (Figure 6g). The robust interaction between the PdCo nanoclusters and the Co 3 S 4 surface significantly impedes the migration and aggregation of active species, resulting in improved dispersion and uniformity of PdCo nanoclusters throughout the synthesis process.…”