Recent Advances on Transition‐Metal‐Based Layered Double Hydroxides Nanosheets for Electrocatalytic Energy Conversion

Abstract

Transition‐metal‐based layered double hydroxides (TM‐LDHs) nanosheets are promising electrocatalysts in the renewable electrochemical energy conversion system, which are regarded as alternatives to noble metal‐based materials. In this review, recent advances on effective and facile strategies to rationally design TM‐LDHs nanosheets as electrocatalysts, such as increasing the number of active sties, improving the utilization of active sites (atomic‐scale catalysts), modulating the electron configurations, and controlling the lattice facets, are summarized and compared. Then, the utilization of these fabricated TM‐LDHs nanosheets for oxygen evolution reaction, hydrogen evolution reaction, urea oxidation reaction, nitrogen reduction reaction, small molecule oxidations, and biomass derivatives upgrading is articulated through systematically discussing the corresponding fundamental design principles and reaction mechanism. Finally, the existing challenges in increasing the density of catalytically active sites and future prospects of TM‐LDHs nanosheets‐based electrocatalysts in each application are also commented.

Anchoring hydroxyl intermediate on NiCo(OOH)x nanosheets to enable highly efficient electrooxidation of benzyl alcohols

“…The catalyst surface was occupied by BAL molecules to capture the oxidation intermediates and promote the new electrooxidation reaction. Furthermore, the ring current curves were collected by fixing the ring potential in 1 M KOH with 100 mM BAL to reflect the reaction of 4OH − → O 2 + 2H 2 O + 4e − 41–43 . Applying a ring potential of 1.60 V RHE , the average ring current was 24.2 μA in 100 mM BAL in Figure 3F, which was far less than that of 145.1 μA in KOH without BAL for a desirable four electron pathway of OER (Figure S10b).…”

“…O 2 + 2H 2 O + 4e À . [41][42][43] Applying a ring potential of 1.60 V RHE , the average ring current was 24.2 μA in 100 mM BAL in Figure 3F, which was far less than that of 145.1 μA in KOH without BAL for a desirable four electron pathway of OER (Figure S10b). The result meant that the electrooxidation precedes of BAL the O 2 -generated from OER.…”

Hollow Starlike Ag/CoMo-LDH Heterojunction with a Tunable d-Band Center for Boosting Oxygen Evolution Reaction Electrocatalysis

“…Electrolytic water splitting holds promising potential as a technology for generating high-purity hydrogen (H 2 ) through the hydrogen evolution process (HER) at the cathode, and simultaneously producing oxygen (O 2 ) for direct medical applications through the oxygen evolution reaction (OER) at the anode. − However, the efficiency of this system ultimately depends on the OER owing to its kinetically sluggish four-electron-transfer process. ,− As a result, great efforts have been made to unravel electrocatalysts with high efficiency, aiming to enhance the OER and reduce the overpotential. Meanwhile, the promoted OER can also provide more solutions to explore other green technologies for energy conversion, such as CO 2 reduction and metal–air batteries. − Unfortunately, the traditional iridium/ruthenium oxides are economically unfriendly and restricted to large-scale application due to their low reserves.…”

“…To overcome this challenge, massive research has been conducted to investigate non-noble metal materials with different phases and advanced structures for catalyzing the OER. Among these materials, metal hydroxides, commonly referred to as layered double hydroxides (LDHs), stand out with their controllable compositions, appealing physicochemical properties, and easily accessible synthesis methods. − Nevertheless, insufficient active sites, impeditive electronic/ionic transport, and limited per-site catalytic ability are the main obstacles for bulky LDHs to deliver satisfactory electrocatalytic OER performance. ,, …”

“…To enhance the intrinsic activity on each site, the heterostructure interface is one key to modify the electronic structure/oxidation state of an active metal center with optimal adsorption energies for OER intermediates according to the common adsorbate evolution mechanism. ,, Over the past years, loading noble metal entities onto LDH substrates to form heterojunctions would lead to activity enhancement, in which noble metal components as mediators can tailor the electronic structure of metal sites . For example, Zhang and co-workers pioneeringly decorated Au single atoms on NiFe-LDH to redistribute the Au-to-LDH charge, facilitating OER active oxyhydroxide and its corresponding adsorption ability .…”