Electronic and Morphological Dual Modulation of Cobalt Carbonate Hydroxides by Mn Doping toward Highly Efficient and Stable Bifunctional Electrocatalysts for Overall Water Splitting

Abstract

Developing bifunctional efficient and durable non-noble electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is highly desirable and challenging for overall water splitting. Herein, Co-Mn carbonate hydroxide (CoMnCH) nanosheet arrays with controllable morphology and composition were developed on nickel foam (NF) as such a bifunctional electrocatalyst. It is discovered that Mn doping in CoCH can simultaneously modulate the nanosheet morphology to significantly increase the electrochemical active surface area for exposing more accessible active sites and tune the electronic structure of Co center to effectively boost its intrinsic activity. As a result, the optimized CoMnCH/NF electrode exhibits unprecedented OER activity with an ultralow overpotential of 294 mV at 30 mA cm, compared with all reported metal carbonate hydroxides. Benefited from 3D open nanosheet array topographic structure with tight contact between nanosheets and NF, it is able to deliver a high and stable current density of 1000 mA cm at only an overpotential of 462 mV with no interference from high-flux oxygen evolution. Despite no reports about effective HER on metal carbonate hydroxides yet, the small overpotential of 180 mV at 10 mA cm for HER can be also achieved on CoMnCH/NF by the dual modulation of Mn doping. This offers a two-electrode electrolyzer using bifunctional CoMnCH/NF as both anode and cathode to perform stable overall water splitting with a cell voltage of only 1.68 V at 10 mA cm. These findings may open up opportunities to explore other multimetal carbonate hydroxides as practical bifunctional electrocatalysts for scale-up water electrolysis.

Boosting Electrochemical Water Oxidation with Metal Hydroxide Carbonate Templated Prussian Blue Analogues

“…[25] Thev ariation in the position of the pre-peaks can be explained by the different electron environment around the metal centers ( Figure 2). [27] This clearly shows the superiority of the templated approach to obtain high current density at low overpotential. Only 240 mV overpotential is required for t-Co II -Co III to reach the anodic current density of 10 mA cm À2 .Importantly,the water oxidation current density obtained for t-Co II -Co III is far better than the template-free catalyst f-Co II -Co III under similar reaction conditions.Moreover,the templated catalyst outperforms the water oxidation activity of the noble metal catalyst RuO 2 in alkaline medium and many other carbon cloth supported first-row transition-metal catalysts reported previously (Supporting Information, Table S2).…”

“…As the t-Co II -Co III is transformed into al ayered hydroxide structure during OER (see later), we have compared the activity with reported layered double hydroxide catalysts and better performance of our catalyst is observed (Supporting Information, Table S2). [27] This clearly shows the superiority of the templated approach to obtain high current density at low overpotential. Thea ctivity of the templated PBAa lso surpasses the PBAd erived electrocatalysts like phosphides,s ulfides,n anoalloys,o ro xides prepared by high temperature multistep method (Supporting Information, Table S2).…”

Fe‐Doped Ni3S2 Nanowires with Surface‐Restricted Oxidation Toward High‐Current‐Density Overall Water Splitting

“…Electrocatalytic water splitting into hydrogen and oxygen provides a prospective and competitive technology to generate sustainable and renewable energy sources. [1][2][3] Nevertheless, the high overpotentials of both half-cell reaction, i. e., hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), heavily restrict a real application of overall water splitting. [4] Up to now, the benchmark catalyst for OER is IrO 2 or RuO 2 , while that for HER is Pt/C due to their high activities.…”

Bimetal−Organic Framework Derived High‐Valence‐State Cu‐Doped Co3O4 Porous Nanosheet Arrays for Efficient Oxygen Evolution and Water Splitting

“…To achieve this goal, building well-aligned arrays of active components on three-dimensional (3D) conductive current collectors seems to be a useful approach, since it can expose large specific surface areas to allow easy spread of ions and therefore increases intrinsic activity of the active sites toward catalysis applications. [36][37][38][39][40] For instance, Qiao and co-workers [41] boosted the OER activity of Co 3 O 4 by directly grown porous Co 3 O 4 -based nanowire arrays on Cu foil. Li et al [42] also fabricated interconnected Co 3 Few reports demonstrated the design of maximizing the relative content of active Co 3 + species of to get benefit in the OER process.…”