Synergetic Metal Defect and Surface Chemical Reconstruction into NiCo₂S₄/ZnS Heterojunction to Achieve Outstanding Oxygen Evolution Performance

Abstract

Defect and interface engineering are recognized as effective strategies to regulate electronic structure and improve activity of metal sulfide. However, the practical application of sulfide is restricted by their low conductivity and rapid decline in activity derived from large volume fluctuation during electrocatalysis process. More importantly, the determination of exact active site of sulfide is complicated due to the inevitable electrochemical reconstruction. Herein, ZnS nanoparticles with Zn defect are anchored onto the surface of NiCo2S4 nanosheet to construct NiCo2S4/ZnS hybrids, which exhibit outstanding oxygen evolution performance with an ultralow overpotential of 140 mV. The anchoring of defective ZnS nanoparticles inhibit the volume expansion of NiCo2S4 nanosheet during the cycling process. Density‐functional theory reveals that the build‐in interfacial potential and Zn defect can facilitate the thermodynamic formation of *O to *OOH, thus improve their intrinsic activity.

Newly Designed One‐Pot In‐Situ Synthesis of VS2/rGO Nanocomposite to Explore Its Electrochemical Behavior towards Oxygen Electrode Reactions**

“…The reversibility and the bifunctional catalytic activity of the oxygen electrodes are usually calculated from the potential difference between the OER current density at 10 mA/cm 2 ( E j10,OER ) and the half‐wave potential ( E 1/2,ORR ) of the ORR current density (Table S3) according to the equation: ΔE = E j10,OER – E 1/2,ORR . For a better bifunctional catalytic activity of a catalyst, ΔE should be smaller and thus, it becomes more promising for practical applications, as compared with some reported literature values (Table S4) [63,66] . Among the as‐prepared catalysts, VS 2 /rGO demonstrates the smallest ΔE value of 0.75 V. The overall result demonstrates that rGO significantly enhances the bifunctional ORR/OER activity of VS 2 thereby, promoting the adsorption of oxygenated intermediates on both VS 2 and rGO surfaces.…”

Aqueous Methanol to Formaldehyde and Hydrogen on Pd/TiO2 by Photocatalysis in Direct Sunlight: Structure Dependent Activity of Nano-Pd and Atomic Pt-Coated Counterparts

“…This also underscores the electronic integration of cocatalyst with TiO 2 , which is supported by different spectral and microscopy analysis and could be the reason for the enhanced activity. It is also worth mentioning the synergy effect between the surface structure of Pd and Pt for better HCHO activity rather than the metal–support (TiO 2 ) interaction; − while the former decides the overpotential of the redox reaction, the latter decides the metal–semiconductor junction and hence electron–hole pair separation/diffusion. As indicated earlier, the (111) surface facets of Pd TO lead to a similar structure with deposited Pt, which exhibits higher oxidation activity.…”

“…Reports are also available on the core–shell catalysts for different applications such as catalytic, electrocatalytic, and photocatalytic reactions. ,, For instance, Bai et al, reported the tuning of Pt shell thickness over a Pd core, and it is possible to produce highly active and stable cocatalysts with titania for photocatalytic hydrogen generation due to enhanced charge separation features . In fact, it is well established in the literature that the synergetic effects of various components has been demonstrated for improved performance of various catalytic reactions. − Particular attention is paid to understand the changes in surface properties and its correlation to the photocatalytic results observed in the present work.…”

Porous Indium Tin Oxide-Supported NiFe LDH as a Highly Active Electrocatalyst in the Oxygen Evolution Reaction and Flexible Zinc–Air Batteries

“…Based on the problems discussed above, nonprecious-metal-based catalysts with acceptable price, benign activity, and superior stability have been widely studied during the past decades. − Transition-metal-based (oxy)­hydroxides might be an alternative to precious-metal-based catalysts in alkaline media due to their tunable electronic properties, earth-abundant resources, and easy synthesis routes. − Tuning the electronic structures by doping or creating vacancies to meet the smallest free energy for *OH and *OOH is an efficient way to lower the overpotential of the OER. In this sense, nickel- and cobalt-based hydroxides are widely studied because of their high catalytic activity and adjustable electronic structure. , For example, Qiu et al doped NiO with Fe and found that the overpotential at 10 mA/cm 2 for Fe–NiO/NF was only 305 mV .…”