CoP/Fe‐Co₉S₈ for Highly Efficient Overall Water Splitting with Surface Reconstruction and Self‐Termination

Abstract

Highly efficient electrochemical water splitting is of prime importance in hydrogen energy but is suffered from the slow kinetics at the anodic oxygen evolution reaction. Herein, combining the surface activation with the heterostructure construction strategy, the CoP/Fe-Co 9 S 8 heterostructures as the pre-catalyst for highly efficient oxygen evolution are successfully synthesized. The catalyst only needs 156 mV to reach 10 mA cm −2 and keeps stable for more than 150 h. Inductively coupled plasma optical emission spectrometry, in situ Raman spectroscopy and density functional theory calculations verify that the introduction of Fe can promote the formation of highly active Co(IV)-O sites and lead to a self-termination of surface reconstruction, which eventually creates a highly active and stable oxygen evolution catalytic surface. Besides, the catalyst also demonstrates high hydrogen evolution reaction activity with an overpotential of 62 mV@10 mA cm −2 . Benefiting from its bifunctionality and self-supporting property, the membrane electrode assembly electrolyzer equipped with these catalysts achieves high overall water splitting efficiency of 1.68 V@1 A cm −2 .

Understanding the Anion Effect of Basic Cobalt Salts for the Electrocatalytic Oxygen Evolution Reaction

“…When the applied potential was increased to 1.3 V, Raman peaks corresponding to Co­(III) and Co­(IV) at 472 and 560 cm –1 appeared in the spectra of Co­(OH)­(CO 3 ) 0.5 . Similar phase transitions occurred in Co 2 (OH) 3 Cl and Co­(OH)­F, − but Raman peaks of Co­(IV) emerged when the applied potential reached 1.4 V, while the significant variation in the signal peak between 600 and 700 cm –1 could be attributed to the presence of CoOOH or other CoOx species. − As expected, the in situ Raman data again support that Co­(II) on the surface of Co­(OH)­(CO 3 ) 0.5 is more easily reconstructed to be high-valent Co­(IV) species, which favors enhanced OER catalysis. Based on the above characterizations, the structure evolution of all the Co­(OH) x (A) y during OER has been uncovered.…”

MnOxHy-modified CoMoP/NF nanosheet arrays as hydrogen evolution reaction and oxygen evolution reaction bifunctional catalysts under alkaline conditions

“…2d), for the CoMoP/NF precursor, the 2p 3/2 and 2p 1/2 peaks of Co 3+ were located at 782.5 and 798.8 eV, respectively, and the 2p 3/2 and 2p 1/2 peaks of Co 2+ were located at 784.1 and 801 eV, respectively, as well as the satellite peaks (785.6 eV/803.1 eV). 46 In contrast, after electrodeposition of the precursor, the 2p 3/2 and 2p 1/2 peaks of Co 3+ are located at 782.2 and 798.6 eV, respectively, while the 2p 3/2 and 2p 1/2 peaks of Co 2+ are located at 783.8 and 800.6 eV, respectively, with a negative shift of 0.2 eV. This shift indicated a change in the chemical environment of Co due to the modification by MnO x H y , resulting in strong electronic interactions between atomic centers and leading to a favorable adsorption energy of H for the HER.…”

Rational design of efficient electrocatalysts for hydrogen production by water electrolysis at high current density

“…109 Due to the alkaline operating environment, nonprecious metal-based materials are effectively employed as electrocatalysts, significantly reducing the catalyst cost. [115][116][117][118][119] Compared with PEMWE operating under a corrosive acidic environment, the high-current-density stability could be improved for AEMWE in alkaline electrolytes. 64 However, the low maximum achievable current density caused by sluggish kinetics imposes limitations on the large-scale H 2 production using AEMWE.…”