Plasma‐induced Mo‐doped Co₃O₄ with enriched oxygen vacancies for electrocatalytic oxygen evolution in water splitting

Abstract

Heteroatomic substitution and vacancy engineering of spinel oxides can theoretically optimize the oxygen evolution reaction (OER) through charge redistribution and d‐band center modification but still remain a great challenge in both the preparation and catalytic mechanism. Herein, we proposed a novel and efficient Ar‐plasma (P)‐assisted strategy to construct heteroatom Mo‐substituted and oxygen vacancies enriched hierarchical spinel Co3O4 porous nanoneedle arrays in situ grown on carbon cloth (denoted P‐Mo‐Co3O4@CC) to improve the OER performance. Ar‐plasma technology can efficiently generate vacancy sites at the surface of hydroxide, which induces the anchoring of Mo anion salts through electrostatic interaction, finally facilitating the substitution of Mo atoms and the formation of oxygen vacancies on the Co3O4 surface. The P‐Mo‐Co3O4@CC affords a low overpotential of only 276 mV at 10 mA cm−2 for the OER, which is 58 mV superior to that of Mo‐free Co3O4@CC and surpasses commercial RuO2 catalyst. The robust stability and satisfactory selectivity (nearly 100% Faradic efficiency) of P‐Mo‐Co3O4@CC for the OER are also demonstrated. Theoretical studies demonstrate that Mo with variable valance states can efficiently regulates the atomic ratio of Co3+/Co2+ and increases the number of oxygen vacancies, thereby inducing charge redistribution and tuning the d‐band center of Co3O4, which improve the adsorption energy of oxygen intermediates (e.g., *OOH) on P‐Mo‐Co3O4@CC during OER. Furthermore, the two‐electrode OER//HER electrolyzer equipped with P‐Mo‐Co3O4@CC as anode displays a low operation potential of 1.54 V to deliver a current density of 10 mA cm−2, and also exhibits good reversibility and anticurrent fluctuation ability under simulated real energy supply conditions, demonstrating the great potential of P‐Mo‐Co3O4@CC in water electrolysis.

Neodymium‐Evoked Valence Electronic Modulation to Balance Reversible Oxygen Electrocatalysis

“…Conversely, the RDS of OER is the transition from *OOH to O 2 and H 2 O, where the huge energy gap is an obstacle for the desorption of *OOH to release O 2 . [ 51,52 ] Additionally, the intrinsic activity of Nd/Co@NC can also be corroborated by the redistributed surface electronic structure. The projected density of states (PDOS) on Co‐3d orbitals of Nd‐doped Co (Figure 6c) reveals that the Nd‐4f orbital and Co‐3d orbital have obvious coupling close to the Fermi level, which optimizes the surface electronic structure for expedited charge transfer.…”

CoS2/MoS2 Hollow Heterostructure as High‐efficiency Bifunctional Electrocatalyst for Overall Water Splitting

“…Firstly, with the increasing of Na 2 MoO 4 , the contents of Co 3 + in CoS 2 /MoS 2 -2 and CoS 2 /MoS 2 -3 are obviously higher than that in CoS 2 /MoS 2 -1, and the high valance Co 3 + has been demonstrated to be beneficial for electrocatalytic performance. [32] Secondly, the composition derived from XPS are listed in Table S1. It can be seen that the content of Mo increased with the increasing of adding Na 2 MoO 4 .…”

In Situ Construction of Cobalt-Doped High-Dispersive Heazlewoodite for Efficient Oxygen Evolution

“…The smaller voltage gap would more likely reduce the energy costs in the water electrolysis. Thus, electrocatalysts are required to reduce the voltage gap between the anode and cathode. − However, the sluggish reaction kinetics of the anodic oxygen evolution reaction (OER) make the water electrolysis voltage much higher than the theoretical 1.23 V versus standard hydrogen electrode (SHE), leading to the difficulty in practical application. − Therefore, research on efficient electrocatalysts to reduce the overpotential of the OER is of vital significance.…”