Nitride or Oxynitride? Elucidating the Composition–Activity Relationships in Molybdenum Nitride Electrocatalysts for the Oxygen Reduction Reaction

Kreider, Melissa E.; Stevens, Michaela Burke; Liu, Yunhzi; Patel, Anjli M.; Statt, Michael J.; Gibbons, Brenna M.; Gallo, Alessandro; Ben-Naim, Micha; Mehta, Apurva; Davis, Ryan C.; Ievlev, Anton V.; Nørskov, Jens K.; Sinclair, Robert; King, Laurie A.; Jaramillo, Thomas F.

doi:10.1021/acs.chemmater.9b05212

Cited by 63 publications

(72 citation statements)

References 95 publications

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“…redox, dissolution, composition changes) that impact catalyst longevity. As shown above (Section 2.1) and by others, 19,27,28,52 nitride materials, e.g. MoN, are particularly sensitive to both air and applied potential.…”

Section: Surface Specific Oxidation Detected By In Situ Grazing Incidence Xas the Surface Of A Catalystsupporting

confidence: 52%

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Identifying and Tuning the In Situ Oxygen-Rich Surface of Molybdenum Nitride Electrocatalysts for Oxygen Reduction

Stevens

Kreider

Patel

et al. 2020

ACS Appl. Energy Mater.

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Rigorous in situ studies of electrocatalysts are required to enable the design of higher performing catalysts. Non-platinum group metals for oxygen reduction (ORR) catalysis containing light elements such as oxygen, nitrogen, and carbon are known to be susceptible to both ex situ and in situ oxidation leading to challenges associated with ex situ characterization methods. We have previously shown that bulk O content plays an important role in the activity and selectivity of Mo-N catalysts, but further understanding the role of composition and morphological changes at the surface is needed. Here, we report the measurement of in situ surface changes to a molybdenum nitride (MoN) thin film under ORR conditions using grazing incidence x-ray absorption and 2 reflectivity. We show that the halfwave potential of MoN can be improved by ~ 90 mV by potential conditioning up to 0.8 V vs RHE. Utilizing electrochemical analysis, dissolution monitoring, and surface sensitive x-ray techniques, we show that under moderate polarization (0.3 -0.7 V vs RHE) there is local ligand distortion, O incorporation, and amorphization of the MoN surface, without changes in roughness. Furthermore, with a controlled potential hold procedure, we show that the surface changes concurrent with potential conditioning are stable under ORR relevant potentials.Conversely, at higher potentials (≥ 0.8 V vs RHE) the film incorporates O, dissolves, and roughens, suggesting that in this higher potential regime the performance enhancements are due to increased access to active sites. Density functional theory calculations and Pourbaix analysis provide insight into film stability and oxygen incorporation as a function of potential. These findings coupled with in situ electrochemical-surface sensitive x-ray techniques demonstrate an approach to studying non-traditional surfaces in which we can leverage our understanding of surface dynamics to improve performance with the rational, in situ tuning of active sites.

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Section: Surface Specific Oxidation Detected By In Situ Grazing Incidence Xas the Surface Of A Catalystsupporting

confidence: 52%

“…The chamber pressure was maintained at 6 mTorr, with a substrate temperature of 180 ± 10 ˚C with a substrate bias of (-) 110 V, and 200 W target power. 19 2.3 Physical Characterization. XPS was performed using a Phi Versaprobe 3 with monochromatized Al Kα (1486 eV) radiation.…”

Section: Synthesismentioning

confidence: 99%

Identifying and Tuning the In Situ Oxygen-Rich Surface of Molybdenum Nitride Electrocatalysts for Oxygen Reduction

Stevens

Kreider

Patel

et al. 2020

ACS Appl. Energy Mater.

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“…Such gallium oxynitrides, as for other reported oxynitrides (TaON, HfON, perovskite oxynitride, etc.) that have hybridization of the N 2p and O 2p orbitals [35][36][37][38][39] , possess better catalytic properties and perform a similar role in the electrocatalyst for better mediating charge transfer. The DFT simulation results were in line with experiments in which replacing the nitrogen atoms by oxygen to form oxynitride can passivate the surface for further stability, whereas the newly formed oxynitride can also provide more active sites for HER, leading to improved PEC performance.…”

mentioning

confidence: 99%

Development of a photoelectrochemically self-improving Si/GaN photocathode for efficient and durable H2 production

et al. 2021

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Development of an efficient yet durable photoelectrode is of paramount importance for deployment of solar-fuel production. Here, we report the photoelectrochemically self-improving behaviour of a silicon/gallium nitride photocathode active for hydrogen production with a Faradaic efficiency approaching ~100%. By using a correlative approach based on different spectroscopic and microscopic techniques, as well as density functional theory calculations, we provide a mechanistic understanding of the chemical transformation that is the origin of the self-improving behaviour. A thin layer of gallium oxynitride forms on the side walls of the gallium nitride grains, via a partial oxygen substitution at nitrogen sites, and displays a higher density of catalytic sites for the hydrogen-evolving reaction. This work demonstrates that the chemical transformation of gallium nitride into gallium oxynitride leads to sustained operation and enhanced catalytic activity, thus showing promise for oxynitride layers as protective catalytic coatings for hydrogen evolution.

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“…The incorporation of nitrogen (N) into oxides opens the facile route of tuning physical and chemical properties [76][77][78]. As N with weaker electronegative and is more polarizable than O, the M-N bond is more covalent than the M-O bond in nature [79].…”

Section: Oxynitridementioning

confidence: 99%

Shining Light on Anion-Mixed Nanocatalysts for Efficient Water Electrolysis: Fundamentals, Progress, and Perspectives

et al. 2022

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Highlights This review introduces recent advances of various anion-mixed transition metal compounds (e.g., nitrides, halides, phosphides, chalcogenides, (oxy)hydroxides, and borides) for efficient water electrolysis applications in detail. The challenges and future perspectives are proposed and analyzed for the anion-mixed water dissociation catalysts, including polyanion-mixed and metal-free catalyst, progressive synthesis strategies, advanced in situ characterizations, and atomic level structure–activity relationship. Abstract Hydrogen with high energy density and zero carbon emission is widely acknowledged as the most promising candidate toward world's carbon neutrality and future sustainable eco-society. Water-splitting is a constructive technology for unpolluted and high-purity H2 production, and a series of non-precious electrocatalysts have been developed over the past decade. To further improve the catalytic activities, metal doping is always adopted to modulate the 3d-electronic configuration and electron-donating/accepting (e-DA) properties, while for anion doping, the electronegativity variations among different non-metal elements would also bring some potential in the modulations of e-DA and metal valence for tuning the performances. In this review, we summarize the recent developments of the many different anion-mixed transition metal compounds (e.g., nitrides, halides, phosphides, chalcogenides, oxyhydroxides, and borides/borates) for efficient water electrolysis applications. First, we have introduced the general information of water-splitting and the description of anion-mixed electrocatalysts and highlighted their complementary functions of mixed anions. Furthermore, some latest advances of anion-mixed compounds are also categorized for hydrogen and oxygen evolution electrocatalysis. The rationales behind their enhanced electrochemical performances are discussed. Last but not least, the challenges and future perspectives are briefly proposed for the anion-mixed water dissociation catalysts.

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Nitride or Oxynitride? Elucidating the Composition–Activity Relationships in Molybdenum Nitride Electrocatalysts for the Oxygen Reduction Reaction

Abstract: Thomas F (2020) Nitride or Oxynitride? Elucidating the Composition-Activity Relationships in Molybdenum Nitride Electrocatalysts for the Oxygen Reduction Reaction. Chemistry of Materials.

Cited by 63 publications

References 95 publications

Identifying and Tuning the In Situ Oxygen-Rich Surface of Molybdenum Nitride Electrocatalysts for Oxygen Reduction

Identifying and Tuning the In Situ Oxygen-Rich Surface of Molybdenum Nitride Electrocatalysts for Oxygen Reduction

Development of a photoelectrochemically self-improving Si/GaN photocathode for efficient and durable H2 production

Shining Light on Anion-Mixed Nanocatalysts for Efficient Water Electrolysis: Fundamentals, Progress, and Perspectives

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