Dual-Ligand Synergistic Modulation: A Satisfactory Strategy for Simultaneously Improving the Activity and Stability of Oxygen Evolution Electrocatalysts

Abstract

The sluggish kinetics of the oxygen evolution reaction (OER) is the bottleneck of water electrolysis for hydrogen generation. Developing cost-effective OER materials with a high value of practical application is a prerequisite to achieve extreme performance in both activity and stability. Herein, we report a "dual ligand synergistic modulation" strategy to accurately tune the structure of transition-metal materials at atomic level, which finally achieves satisfactory results for the unity between robust stability and high activity. Remarkably, the elaborately designed S and OH dual-ligand NiCo 2 (SOH) x catalyst exhibits an excellent OER activity with a very small overpotential of 0.29 V at a current density of 10 mA cm −2 and a strong durability even after 30 h accelerated aging at a large current density of 100 mA cm −2 , both of which are superior to most of the state-of-the-art OER catalysts so far. The density functional theory (DFT) calculations disclose that the synergy of OH and S ligands on the surface of NiCo 2 (SOH) x can delicately tune the electronic structure of metal active centers and their chemical environment, which results in optimal binding energies of the OER intermediates (*OH, *O, and *OOH) and a strengthened binding energy between metal and anion ligands, thus leading to an excellent intrinsically enhanced OER activity and stability, respectively. Meanwhile, the special nonmagnetism of NiCo 2 (SOH) x can significantly weaken the resistance of O 2 desorption on the catalyst surface, thus facilitating the O 2 evolution proceedings.

Boosting H2 Generation Coupled with Selective Oxidation of Methanol into Value‐Added Chemical over Cobalt Hydroxide@Hydroxysulfide Nanosheets Electrocatalysts

“…This is because sulfur specie has smaller electronegativity than O, and can be polarized easily to disperse its electrons to the adjacent Co ions. The regulated electronic structure of active sites by room temperature sulfurization can optimize the adsorption energy of oxygen‐containing reactant and intermediates . Moreover, the binding energy centered at 785.5 eV corresponds to the characteristic peak of the CoS bonding, which further verifies the interaction between Co ions and S 2− .…”

“…More importantly, the durability of CoS x /CP has declined sharply during 15 h (Figure S9b, Supporting Information). Compared with the CoS x , the OH − confined in cobalt hydroxysulfide layer has stronger electronegativity comparing with S 2− , which attracts electrons from the antibonding orbital of metal–S bonds to metal–O bonds and thus making the metal–S bond become shorter and more stable . The energy efficiency is another important parameter that can reveal the percentage of energy input to produce ideal products.…”

Defect‐Rich Nitrogen Doped Co3O4/C Porous Nanocubes Enable High‐Efficiency Bifunctional Oxygen Electrocatalysis

“…The optimized structures with intermediates adsorbed of OER are performed in Figure S17 (Supporting Information). It is well known that the process possessing the largest Δ G i is considered as the PDS for the OER . Based on the Gibbs free energy diagram (Figure c), the second step (O* formation) (Δ G O* = 1.87 eV, η = 0.64 V) is identified as the PDS of OER for pristine Co 3 O 4 .…”

Rational Design of Nanoarray Architectures for Electrocatalytic Water Splitting

“…Owing to low cost, earth abundance, and less toxicity of Fe in comparison with Co and Ni, iron phosphate–borate nanosheet arrays as OER catalysts presented a low overpotential (434 mV) at 10 mA cm −2 and strong stability in 0.1 m KBi . For instance, dual ligand Ni, Co sulfhydroxides as OER catalysts achieved current density of 10 mA cm −2 at a low overpotential and robust stability owing to the synergy between S atoms and OH groups ( Figure a) . Cobalt phosphosulfide (Co 2− x SP) nanosheet on carbon fiber paper substrate by a simple two‐step electrodeposition route showed current density of 10 mA cm −2 at a low overpotential (279 mV), a low Tafel slope (54 mV per decade), and robust stability toward remarkable OER activity .…”