Unlocking the Transition of Electrochemical Water Oxidation Mechanism Induced by Heteroatom Doping

Abstract

Heteroatom doping has emerged as a highly effective strategy to enhance the activity of metal‐based electrocatalysts toward the oxygen evolution reaction (OER). It is widely accepted that the doping does not switch the OER mechanism from the adsorbate evolution mechanism (AEM) to the lattice‐oxygen‐mediated mechanism (LOM), and the enhanced activity is attributed to the optimized binding energies toward oxygen intermediates. However, this seems inconsistent with the fact that the overpotential of doped OER electrocatalysts (< 300 mV) is considerably smaller than the limit of AEM (> 370 mV). To determine the origin of this inconsistency, we select phosphorus (P)‐doped nickel‐iron mixed oxides as the model electrocatalysts and observe that the doping enhances the covalency of the metal‐oxygen bonds to drive the OER pathway transition from the AEM to the LOM, thereby breaking the adsorption linear relation between *OH and *OOH in the AEM. Consequently, the obtained P‐doped oxides display a small overpotential of 237 mV at 10 mA cm−2. Beyond P, the similar pathway transition is also observed on the sulfur doping. These findings offer new insights into the substantially enhanced OER activity originating from heteroatom doping.

Perovskite manganese oxides with tunable metal–oxygen covalency for efficient bisphenol A degradation

“…Then, stoichiometric amounts of metal nitrate were added in the solution with an adequate amount of (CH 2 OH) 2 under thermal stirring (80 °C) until a viscous gel was obtained (for the detailed amount see Table S1†). The electronic structure of Mn is regulated by introducing A-site defects or doping with low valent metals such as Ca, Sr, and K. 26 The molar ratio between ethylene glycol, total metal cations and citric acid is 3 : 1 : 1.5. Then, the obtained sample was dried at 210 °C overnight and calcined at 750 °C for 4 h. LaMnO 3 , La 0.9 MnO 3 , La 0.75 Ca 0.25 MnO 3 , La 0.75 Sr 0.25 MnO 3 and La 0.75 Ca 0.20 K 0.05 MnO 3 were denoted as LMO, L 0.9 MO, LCMO, LSMO and LCKMO, respectively.…”

Recent advances in metal-free electrocatalysts for the hydrogen evolution reaction

“…In a closed reactor, the aqueous solution is used as the reaction system, and the synthesis procedure is controlled by reaction time and temperature. 104–106 Generally, it is often used to synthesize inorganic nanomaterials, but it is also employed to prepare metal-free HER catalysts. For example, Tian et al 107 synthesized the iodine-doped graphene (I-G) sample by using KI as the I source through the one-step hydrothermal method (Fig.…”

Fiber-in-tube RuxCr1−xOy as highly efficient electrocatalysts for pH-universal water oxidation via facile bubble desorption

“…The OER involves the transfer of four electrons and four protons, requiring a higher overpotential to overcome the kinetic barrier compared to the HER, a two-electron transfer reaction. 10–13 In this regard, reducing the kinetic barrier of the OER is a crucial point in enhancing the efficiency of overall water electrolysis. 14 Proton concentration in water electrolysis fluctuates throughout the process, making it essential for an ideal electrocatalyst to operate effectively over a broad range of pH conditions, promoting energy efficiency and reliability.…”