Converting CoMoO₄ into CoO/MoO_x for Overall Water Splitting by Hydrogenation

Abstract

Special structure of materials often bring in unprecedented catalytic activity which are critical in realizing large-scale hydrogen production by electrochemical water splitting.Herein, we report CoO/MoO x crystalline/amorphous structure as an effective bifunctional electrocatalyst for water splitting. Converted from CoMoO 4 by hydrogenation, the CoO/MoO x , featured with crystalline CoO in amorphous MoO x matrix, displays superior catalytic activities toward both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). It shows small onset overpotentials of 40 and 230 mV for the HER and OER in 1.0 M KOH, respectively, and overall water splitting starting at 1.53 V with a robust stability. The high catalytic activity of the CoO/MoO x is benefited from the large defect-rich interface between CoO and MoO x , along with the amorphous nature of MoO x . Thus, this study demonstrates the effectiveness of structural manipulation in developing highly active electrocatalysts for overall electrochemical water splitting.

Binary FeCo Oxyhydroxide Nanosheets as Highly Efficient Bifunctional Electrocatalysts for Overall Water Splitting

“…The FeCoOOH/NF electrode required an overpotential of 126 mV to reach a current density of −10 mA cm −2 . This value was larger than that for the (Pt/C)/NF electrode (60 mV), but lower than those for previously reported bifunctional catalysts, including NiFe LDH (210 mV), NiFe LDH@graphene (300 mV), Ni 5 Fe LDH (133 mV), CoO/MoO x (163 mV), sulfur‐incorporated NiFe 2 O 4 (138 mV), Ni@NiO (153 mV), and Ni 0.75 Fe 0.25 LDH (169 mV) in 1 m KOH or NaOH (Figure E). A Tafel slope of the FeCoOOH nanosheets (79 mV/dec) was larger than that of the Pt/C catalyst (44 mV/dec) (Figure F), but smaller than reported values for NiFe LDH@graphene (110 mV/dec), Ni 5 Fe LDH (89 mV/dec), and Ni@NiO (84 mV/dec) .…”

“…In the electrolyzer based on the FeCoOOH/NF electrodes, the water‐splitting current density of 10 mA cm −2 was reached by applying just 1.62 V across the electrodes without iR compensation (Figure B). The measured overpotential (390 mV) was lower than that for the electrolyzer based on the IrO 2 /NF and (Pt/C)/NF electrodes (408 mV) and those for previously reported alkaline electrolyzers based on bifunctional catalysts including NiFe LDH (470 mV), CoO/MoO x (490 mV), sulfur‐incorporated NiFe 2 O 4 (400 mV), and Ni 0.75 Fe 0.25 LDH (470 mV) in 1 m KOH or NaOH (Figure C). The FeCoOOH/NF‐based electrolyzer produced a current density of 100 mA cm −2 at a cell voltage of 1.84 V without iR correction, which was 120 mV less than the electrolyzer based on the IrO 2 /NF and (Pt/C)/NF electrodes.…”

Metal‐Organic Gel‐Derived Co/CoO/Co3O4 Composite for the Electrochemical Detection of Diethylstilbestrol

“…In addition, electrode materials also played an important role in the electrocatalysis water splitting process owning to the electrode materials could effective decrease the reaction barrier. [11][12][13][14] Although there are many electrode materials have been applied in the field of electrochemistry, the preparation process of those materials still exist some issues such as complicated operation, time consuming and low coupling efficiency. Therefore, exploring a new route to obtain electrode material with excellent electrochemical performance remains a highly challenging task.…”

2D Metallic Transitional Metal Dichalcogenides for Electrochemical Hydrogen Evolution

“…Over the past few decades, advanced electrocatalysts for HER have received extensive attentions, due to exhaustible fossil fuels and the rapid growth of energy consumption. Transition metals [33][34][35][36][37] and their oxides, [33,[38][39][40][41][42][43][44][45][46] hydroxides, [33,[47][48][49][50] chalcogenides, [29,33,[51][52][53][54] phosphides, [33,[55][56][57][58][59][60] and nitrides [33,61] have been reported as promising electrocatalysts to replace noble metals, featured with high activity and earth abundance. Among the candidates, some semiconducting transition metal dichalcogenide (TMDC) materials (e.g., MoS 2 , MoSe 2 , etc.)…”