Water splitting has been widely considered to be an efficient way to generate sustainable and renewable energy resources in fuel cells, metal–air batteries and other energy conversion devices. Exploring efficient electrocatalysts to expedite the anodic oxygen evolution reaction (OER) is a crucial task that needs to be addressed in order to boost the practical application of water splitting. Intensive efforts have been devoted to develop mixed transition metal based chalcogenides as effective OER electrocatalysts. Herein, we have reported synthesis of a series of mixed metal selenides containing Co, Ni and Cu employing combinatorial electrodeposition, and systematically investigated how the transition metal doping affects the OER catalytic activity in alkaline medium. Energy dispersive spectroscopy (EDS) was performed to detect the elemental compositions and confirm the feasibility of compositional control of 66 metal selenide thin films. It was observed that the OER catalytic activity is sensitive to the concentration of Cu in the catalysts, and the catalyst activity tended to increase with increasing Cu concentration. However, increasing the Cu concentration beyond a certain limit led to decrease in catalytic efficiency, and copper selenide by itself, although catalytically active, showed higher onset potential and overpotential for OER compared to the ternary and quaternary mixed metal selenides. Interestingly, the best quaternary composition (Co 0.21 Ni 0.25 Cu 0.54 ) 3 Se 2 showed similar crystal structure as its parent compound of Cu 3 Se 2 with slight decrease in lattice spacings of (101) and (210) lattice planes (0.0222 Å and 0.0148 Å, respectively) evident from the powder X-ray diffraction pattern. (Co 0.21 Ni 0.25 Cu 0.54 ) 3 Se 2 thin film exhibited excellent OER catalytic activity and required an overpotential of 272 mV to reach a current density of 10 mA cm −2 , which is 54 mV lower than Cu 3 Se 2 , indicating a synergistic effect of transition metal doping in enhancing catalytic activity.
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Tuning the intrinsic catalytic activities of oxygen-evolution catalysts by doping: a comprehensive review
Electrochemical water splitting produces clean hydrogen fuel as one of the pivotal alternative energies to fossil fuels in the near future. However, the anodic oxygen evolution reaction (OER) is a significant bottleneck that curtails large-scale applications of electrochemical water splitting technology, owing to its sluggish reaction kinetics. In the past few decades, various methods have been proposed to improve the OER kinetics. Among them, doping is a simple and efficient method to mold the OER kinetics of a catalyst by incorporating different or hetero atoms into the host lattice. These efforts are vital to design highly efficient OER catalysts for real-world applications. However, the OER mechanism of a doped catalyst varies, depending on the host lattice and the dopant. This review highlights different doping strategies and associated OER mechanisms of state-of-the-art catalysts, including oxides (noble metal oxides, perovskite oxides, spinel oxides, hydroxides and others), non-oxides (metal sulfides, metal selenides, metal phosphides, metal nitrides and metal carbides), and carbon-based catalysts (graphene, carbon nanotubes and others). Fundamental understanding of the doping effects on the OER from combined experimental and theoretical research provides guidelines for designing efficient catalysts.
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- Award ID(s):
- 1827731
- NSF-PAR ID:
- 10299491
- Date Published:
- Journal Name:
- Journal of Materials Chemistry A
- Volume:
- 9
- Issue:
- 36
- ISSN:
- 2050-7488
- Page Range / eLocation ID:
- 20131 to 20163
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Gerard Parking (Ed.)The oxygen evolution reaction (OER) of water splitting is essential to electrochemical energy storage applications. While nickel electrodes are widely available heterogeneous OER catalysts, homogeneous nickel catalysts for OER are underexplored. Here we report two carbene-ligated nickel(II) complexes that are exceptionally robust and efficient homogeneous water oxidation catalysts. Remarkably, these novel nickel complexes can assemble a stable thin film onto a metal electrode through poly-imidazole bridges, making them supported heterogeneous electrochemical catalysts that are resilient to leaching and stripping. Unlike molecular catalysts and nanoparticle catalysts, such electrode-supported metal-complex catalysts for OER are rare and have the potential to inspire new designs. The electrochemical OER with our nickel-carbene catalysts exhibits excellent current densities with high efficiency, low Tafel slope, and useful longevity for a base metal catalyst. Our data show that imidazole carbene ligands stay bonded to the nickel(II) centers throughout the catalysis, which allows the facile oxygen evolution.more » « less
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Abstract Based on the coincident onsets of oxygen evolution reaction (OER) and metal dissolution for many metal‐oxide catalysts it was suggested that OER triggers dissolution. It is believed that both processes share common intermediates, yet exact mechanistic details remain largely unknown. For example, there is still no clear understanding as to why rutile IrO2exhibits such an exquisite stability among water‐splitting electrocatalysts. Here, we employ density functional theory calculations to analyze interactions between water and the (110) surface of rutile RuO2and IrO2as a response to oxygen evolution involving lattice oxygen species. We observe that these oxides display qualitatively different interfacial behavior that should have important implications for their electrochemical stability. Specifically, it is found that IrO2(110) becomes further stabilized under OER conditions due to the tendency to form highly stable low oxidation state Ir(III) species. In contrast, Ru species at RuO2(110) are prone to facile reoxidation by solution water. This should facilitate the formation of high Ru oxidation state intermediates (>IV) accelerating surface restructuring and metal dissolution.
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Energy harvesting from solar and water has created ripples in materials energy research for the last several decades, complemented by the rise of Hydrogen as a clean fuel. Among these, water electrolysis leading to generation of oxygen and hydrogen, has been one of the most promising routes towards sustainable alternative energy generation and storage, with applications ranging from metal-air batteries, fuel cells, to solar-to-fuel energy conversion systems. In fact, solar water splitting is one of the most promising method to produce Hydrogen without depleting fossil-fuel based natural resources. However, the efficiency and practical feasibility of water electrolysis is limited by the anodic oxygen evolution reaction (OER), which is a kinetically sluggish, electron-intensive uphill reaction. A slow OER process also slows the other half- cell reaction, i.e. the hydrogen evolution reaction (HER) at the cathode. Hence, designing efficient catalysts for OER process from earth-abundant resources has been one of the primary concerns for advancing solar water splitting. In the Nath group we have focused on transition metal chalcogenides as efficient OER electrocatalysts. We have proposed the idea that these chalcogenides, specifically, selenides and tellurides will show much better OER catalytic activity due to increasing covalency around the catalytically active transition metal site, compared to the oxides caused by decreasing electronegativity of the anion, which in turn leads to variation of chem. potential around the transition metal center, [e.g. lowering the Ni 2+ --> Ni 3+ oxidn. potential in Ni-based catalysts where Ni 3+ is the actually catalytically active species]. Based on such hypothesis, we have synthesized a plethora of transition metal selenides including those based on Ni, Ni-Fe, Co, and Ni-Co, which show high catalytic efficiency characterized by low onset potential and overpotential at 10 mA/cm 2 [Ni 3 Se 2 - 200 - 290 mV; Co 7 Se 8 - 260 mV; FeNi 2 Se 4 -NrGO - 170 mV (NrGO - N-doped reduced graphene oxide); NiFe 2 Se 4 - 210 mV; CoNi 2 Se 4 - 190 mV; Ni 3 Te 2 - 180 mV].more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D1TA04032D
