Low-cost Electrocatalysts For Oxygen Evolution Reaction Research Articles

Zirconium-Regulation-Induced Bifunctionality in 3D Cobalt-Iron Oxide Nanosheets for Overall Water Splitting.

The design of high-efficiency non-noble bifunctional electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is paramount for water splitting technologies and associated renewable energy systems. Spinel-structured oxides with rich redox properties can serve as alternative low-cost OER electrocatalysts but with poor HER performance. Here, zirconium regulation in 3D CoFe2 O4 (CoFeZr oxides) nanosheets on nickel foam, as a novel strategy inducing bifunctionality toward OER and HER for overall water splitting, is reported. It is found that the incorporation of Zr into CoFe2 O4 can tune the nanosheet morphology and electronic structure around the Co and Fe sites for optimizing adsorption energies, thus effectively enhancing the intrinsic activity of active sites. The as-synthesized 3D CoFeZr oxide nanosheet exhibits high OER activity with small overpotential, low Tafel slope, and good stability. Moreover, it shows unprecedented HER activity with a small overpotential of 104 mV at 10 mA cm-2 in alkaline media, which is better than ever reported counterparts. When employing the CoFeZr oxides nanosheets as both anode and cathode catalysts for overall water splitting, a current density of 10 mA cm-2 is achieved at the cell voltage of 1.63 V in 1.0 m KOH.

Se-Doping Activates FeOOH for Cost-Effective and Efficient Electrochemical Water Oxidation.

Ni or Co is commonly required in efficient electrocatalysts for oxygen evolution reaction (OER). Although Fe is much more abundant and cheaper, full-Fe or Fe-rich catalysts suffer from insufficient activity. Herein, we discover that Se-doping can drastically promote OER on FeOOH and develop a facile on-site electrochemical activation strategy for achieving such a Se-doped FeOOH electrode via an FeSe precatalyst. Theoretical analysis and systematic experiments prove that Se-doping enables FeOOH as an efficient and low-cost OER electrocatalyst. By optimizing the electrode structure, an industrial-level OER current output of 500 mA cm-2 is secured at a low overpotential of 348 mV. The application of such an Fe-rich OER electrode in a practical solar-driven water splitting system demonstrates a high and stable solar-to-hydrogen efficiency of 18.55%, making the strategy promising for exploring new cost-effective and highly active electrocatalysts for clean hydrogen production.

Towards highly efficient and low-cost oxygen evolution reaction electrocatalysts: An effective method of electronic waste management by utilizing waste Cu cable wires

Currently, electronic waste (e-waste) is the world’s most challenging and rapidly growing problem in the waste stream. To develop an alternative way to use e-waste (waste copper (Cu) wires) to accelerate the oxygen evolution reaction (OER) of water electrolysis, the waste Cu wires are used as a low-cost current collector. We demonstrate a simple electrodeposition process to deposit nickel-iron hydroxide (NiFe LDH) nanosheets on self-supported copper hydroxide (Cu(OH)2/Cu) nanowires grown via chemical-oxidation on waste Cu wire. Benefiting from the efficient electron transport, high mass activity, and surface area this electrocatalyst exhibits an efficient OER performance with a low overpotential of 275 mV and 390 mV at 20 and 100 mA cm−2 respectively, with excellent stability. This work provides a promising pathway to recycle e-waste into value-added resources in various energy conversion applications.

A facile strategy to construct CoOx in situ embedded nanoflowers as an efficient electrocatalyst for oxygen evolution reaction

With a growing demand for clean and renewable energy associated with water splitting, regenerative fuel cells, metal-air batteries, etc., exploring an efficient and cost-effective electrocatalyst with superior durability for oxygen evolution reaction (OER) is of great significance. In this study, a unique CoOx embedded nanoflower microstructure (Co0.6-PyNa) has been synthesized via an extremely facile one-step, highly scalable aqueous method under mild conditions, by using Co(COOH)2 as the precursor and pyrrole as the structure-directing agent. The Co0.6-PyNa exhibits the excellent electrocatalytic activity toward OER in 1 M KOH solution with an overpotential of as low as 299 mV and a small Tafel slope of 67 mV dec−1, which is comparable to the commercial RuO2, along with superior operational stability to RuO2. The high OER catalytic performance of Co0.6-PyNa has been reasoned to originate from the exposure of abundant CoOx active species uniformly dispersed on the nanoflakes due to its high specific surface area and the intrinsic extraordinarily high activity of CoOx active species. This work provides a promising strategy to fabricate efficient, stable and low-cost OER electrocatalyst, which is expected to promote the development of OER-related energy storage and conversion technologies.

Template-Free Synthesis of Hollow Iron Phosphide–Phosphate Composite Nanotubes for Use as Active and Stable Oxygen Evolution Electrocatalysts

The oxygen evolution reaction (OER) is a half-cell reaction that is of importance to many electrochemical processes, especially for electrochemical and photoelectrochemical water splitting. Developing efficient, durable, and low-cost OER electrocatalysts comprising Earth-abundant elements has been in the focus of electrocatalysis research. Herein, we report a cost-effective, scalable, and template-free approach to the fabrication of hollow iron phosphide–phosphate (FeP–FePxOy) composite nanotubes (NTs), which is realized by hydrothermal growth of iron oxy-hydroxide nanorods (NRs) and a subsequent postphosphorization treatment. The hollow interior of NTs results from the Kirkendall effect occurring upon phosphorization. When used to catalyze the OER in basic medium, the as-synthesized FeP–FePxOy composite NTs exhibit excellent catalytic activity, delivering the benchmark current density of 10 mA cm–2 at a low overpotential of 280 mV and showing a small Tafel slope of 48 mV dec–1 and a high turnover frequen...

Microwave-assisted synthesis of the cobalt-iron phosphates nanosheets as an efficient electrocatalyst for water oxidation

Electrochemical water splitting involves two half-cell reactions, that is oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), and the overall reaction is severely restricted by the OER sluggish kinetics. Hence, to design and develop superior active and low-cost OER electrocatalyst is of significant necessary. In this study, the bimetallic cobalt-iron phosphates nanosheets (denoted as Co-Fe-P-O) with high activity toward OER has been constructed via a rapid microwave-assisted process using sodium hypophosphite and ethylene glycol as the phosphorus source and reaction solvent, respectively. Due to the structural feature of a larger electrochemical active surface area, the catalyst exerts a small overpotential of 267 mV at a current density of 10 mA cm−2 and a low Tafel slope of 30 mV dec−1 in 1.0 M KOH solution. The as-prepared catalyst also shows an outstanding stability with a current density retention of 94% at a constant water oxidation for almost 10 h. All of the results suggest that the performance of the catalyst prepared in our work is better than the state-of-the-art commercial RuO2 and even can rival most of transition metal-based material.

CoOx functionalized IrO2-Sb2O5-SnO2 anode with an enhanced activity and stability for electrocatalytic oxygen evolution

Preparation of highly efficient and inexpensive electrodes for oxygen evolution reaction (OER) is of significant importance in the development of water splitting for hydrogen production. Ternary IrO2-Sb2O5-SnO2 and cobalt-based oxides have been suggested to be high stability and low cost electrocatalysts for OER in acid and basic aqueous solution, respectively. Herein, we develop a serial of Ti/CoOx-IrO2-Sb2O5-SnO2 anodes by a simple thermal treatment of mixed metal chlorides on Ti substrate. It is found that the partial-substitution iridium by cobalt in Ti/Ir0.1Sb0.1Sn0.8Ox (Ti/C0ISS) anode shows an improved OER activity in acid and basic solution. For a Ti/Ir0.05Co0.05Sb0.1Sn0.8Ox (Ti/C5ISS) anode, small overpotentials of 0.438 and 0.498 V are needed under the current densities of 10 and 100 mA cm−2 in 0.5 M KOH, respectively. These values are remarkably lower than those of Ti/C0ISS electrode and comparable to other nanometer metal oxides catalysts. Additionally, it exhibits a low Tafel slope of 55 mV dec−1 and displays excellent electrocatalytic durability for OER in alkaline solution under a high current density. These advantages indicate Ti/C5ISS is a promising anode for water oxidation under high current densities.