Etching‐Doping Sedimentation Equilibrium Strategy: Accelerating Kinetics on Hollow Rh‐Doped CoFe‐Layered Double Hydroxides for Water Splitting

Abstract

Exploring highly active and inexpensive bifunctional electrocatalysts for water‐splitting is considered to be one of the prerequisites for developing hydrogen energy technology. Here, an efficient simultaneous etching‐doping sedimentation equilibrium (EDSE) strategy is proposed to design and prepare hollow Rh‐doped CoFe‐layered double hydroxides for overall water splitting. The elaborate electrocatalyst with optimized composition and typical hollow structure accelerates the electrochemical reactions, which can achieve a current density of 10 mA cm−2 at an overpotential of 28 mV (600 mA cm−2 at 188 mV) for hydrogen evolution reaction (HER) and 100 mA cm−2 at 245 mV for oxygen evolution reaction (OER). The cell voltage for overall water splitting of the electrolyzer assembled by this electrocatalyst is only 1.46 V, a value far lower than that of commercial electrolyzer constructed by Pt/C and RuO2 and most reported bifunctional electrocatalysts. Furthermore, the existence of Fe vacancies introduced by Rh doping and the typical hollow structure are demonstrated to optimize the entire HER and OER processes. EDSE associates doping with template‐directed hollow structures and paves a new avenue for developing bifunctional electrocatalysts for overall water splitting. It is also believed to be practical in other catalysis fields as well.

Facile Synthesis of Two‐Dimensional Iron/Cobalt Metal–Organic Framework for Efficient Oxygen Evolution Electrocatalysis

“…As shown in Figure 3a,b,2 DM OF-Fe/Co(1:2) had the lowest overpotential (238 mV) of 10 mA cm À2 ,t he lowest Tafel slope (52 mV dec À1 ), the largest C dl (66.9 mF cm 2 ), and the smallest R s (7.7 W)a nd R ct (3.3 W), as compared with MOF-Fe/Co(1:3), MOF-Fe/Co(1:1), MOF-Co, MOF-Fe, and RuO 2 (Supporting Information, Figures S8-S11). According to the experimental result, it is concluded that incorporation of Fe in MOF-Co could improve the conductivity and OER activity owing to the partial-charge transfer activation effect of Co. [1,19,31,32] Since the 2D MOF-Fe/Co(1:2) possessed the highest OER performance,i ti sn ecessary to understand the OER mechanism. After several CV cycling, there was asignificant change in the color of the 2D MOF-Fe/ Co(1:2) nanosheets,i.e., from orange to black (see the inset of Figure 3f).…”

“…In recent years, cheap and efficient electrocatalysts based on non‐noble metals, especially transition‐metal (Ni, Co, Fe, etc.) compounds, have been widely studied for the oxygen evolution reaction (OER), owing to their elemental abundance in nature and low costs [1–4] . Metal–organic frameworks (MOFs) based on transition metal ions and organic ligands, having a well‐defined porous structure and a very large specific surface area, can endow them with multiple active sites in water oxidation (i.e., OER).…”

“…)c ompounds,h ave been widely studied for the oxygen evolution reaction (OER), owing to their elemental abundance in nature and low costs. [1][2][3][4] Metal-organic frameworks (MOFs) based on transition metal ions and organic ligands, having aw ell-defined porous structure and av ery large specific surface area, can endow them with multiple active sites in water oxidation (i.e., OER). Meanwhile,t he metal ions supported and protected by the organic framework can ensure along-term stability.However,bulk MOF with nanopores still suffer from poor conductivity and low mass permeability,w hich hamper their application in electrocatalysis.C ompared with bulk MOFs,t he two-dimensional (2D) MOF nanosheets with nanometer layers could possess ahigh electrocatalytic activity owing to many unsaturated coordination sites of metal ions on the surface,a sw ell as the rapid mass transport and charge transfer.…”

Transforming Damage into Benefit: Corrosion Engineering Enabled Electrocatalysts for Water Splitting

“…The importation of precious metal ions into hydroxides can effectively regulate the intrinsic electronic structure, leading to optimize the OER property. [ 140–143 ] It is fairly easy to realize the target of importing precious metal ions through corrosion engineering. For example, Hao et al.…”

Facile Synthesis of Two‐Dimensional Iron/Cobalt Metal–Organic Framework for Efficient Oxygen Evolution Electrocatalysis

“…In recent years, cheap and efficient electrocatalysts based on non‐noble metals, especially transition‐metal (Ni, Co, Fe, etc.) compounds, have been widely studied for the oxygen evolution reaction (OER), owing to their elemental abundance in nature and low costs [1–4] . Metal–organic frameworks (MOFs) based on transition metal ions and organic ligands, having a well‐defined porous structure and a very large specific surface area, can endow them with multiple active sites in water oxidation (i.e., OER).…”