Selectively Etching Vanadium Oxide to Modulate Surface Vacancies of Unary Metal–Based Electrocatalysts for High‐Performance Water Oxidation

Abstract

Electrocatalytic water splitting for hydrogen generation is hindered by the sluggish kinetics of water oxidation, and highly efficient electrocatalysts for the oxygen evolution reaction (OER) are urgently required. Numerous bi‐ and multimetal‐based, low‐cost, high‐performance OER electrocatalysts have been developed. However, unary metal–based high‐performance electrocatalysts are seldom reported. In the present study, Co2(OH)3Cl/vanadium oxide (VOy) composites are synthesized, from which VOy is completely etched out by a simple cyclic voltammetry treatment, which simultaneously transforms Co2(OH)3Cl in situ to ultrafine CoOOH. The selective removal of VOy modulates the nature of the surface in the obtained CoOOH by creating surface oxygen vacancies (Vo), along with disordered grain boundaries. The best‐performing CoOOH with optimum Vo is found to be associated with a low overpotential of 282 mV at 10 mA cm−2 catalytic current density on a simple glassy carbon electrode for OER. This facile protocol of selectively etching VOy to modulate the nature of the surface is successfully applied to synthesize another Fe‐based electrocatalyst with high OER performance, thus establishing its utility for unary metal–based electrocatalyst synthesis.

Recent Progress of Vacancy Engineering for Electrochemical Energy Conversion Related Applications

“…The introduction of various vacancies could enhance catalytic performance for OER and CO 2 RR by decreasing the electrical resistance. [ 61 ] More recently, Sun and co‐workers [ 62 ] prepared CoOOH with various contents of oxygen vacancies by facile cyclic voltammetry (CV) treatment of Co 2 (OH) 3 Cl/VO y to etch VO y ( Figure a). The concentrations of oxygen vacancies were easily controlled by changing the molar ratios of Co and V. As shown in Figure 8b, Co 0.5 (V 0.5 ) exhibited the smallest arc, indicating the lowest charge transfer resistance ( R ct ) at the interface between electrocatalyst and electrolyte.…”

“…Reproduced with permission. [ 62 ] Copyright 2019, Wiley‐VCH. The atomic structure of c) CuCo 2 O 4 and d) V‐CCO.…”

Constructing High Efficiency CoZnxMn2–xO4 Electrocatalyst by Regulating the Electronic Structure and Surface Reconstruction

“…[39] Figure 4g shows the lattice oxygen oxidation mechanism, which includes the adsorption of (OH − ), the formation of OO bonds and * OOH, the release of H 2 O and the * OOH reacts with OH − to release O 2 . According to previous report, [40] the active species of CoOOH for OER is formed through the adsorbate evolution mechanism, indicating that it could be attributed to the oxygen evolution. However, its minimum theoretical overpotential is 0.37 V, [41] which is significantly higher than that of Zn-doped CoMn 2 O 4 catalyst (0.28 V).…”

Synthesis and Electronic Modulation of Nanostructured Layered Double Hydroxides for Efficient Electrochemical Oxygen Evolution

“…As a member of the big family of two‐dimensional (2D) materials, nanostructured layered double hydroxides (nLDHs) have made significant processes and continuous breakthroughs for OER electrocatalysis in recent years [15,24–27] . Due to the advantages of rich exposed active sites, large surface‐to‐bulk ratios, chemical composition tunability, controllable layered nanostructures, and adjustable electronic structures, the nLDHs‐based electrocatalysts have aroused extensive interest for OER in water splitting [28–32] . While considering the dissolution nature of nLDHs in acidic media, the OER process for nLDHs generally occurs under the alkaline condition as shown in Equation (1).…”