Michael Busch

Bio: Michael Busch is an academic researcher from Aalto University. The author has contributed to research in topics: Catalysis & Oxygen evolution. The author has an hindex of 18, co-authored 44 publications receiving 1079 citations. Previous affiliations of Michael Busch include École Polytechnique Fédérale de Lausanne & University of Gothenburg.

An Unconventional Iron Nickel Catalyst for the Oxygen Evolution Reaction.

Abstract: The oxygen evolution reaction (OER) is a key process that enables the storage of renewable energies in the form of chemical fuels. Here, we describe a catalyst that exhibits turnover frequencies higher than state-of-the-art catalysts that operate in alkaline solutions, including the benchmark nickel iron oxide. This new catalyst is easily prepared from readily available and industrially relevant nickel foam, and it is stable for many hours. Operando X-ray absorption spectroscopic data reveal that the catalyst is made of nanoclusters of γ-FeOOH covalently linked to a γ-NiOOH support. According to density functional theory (DFT) computations, this structure may allow a reaction path involving iron as the oxygen evolving center and a nearby terrace O site on the γ-NiOOH support oxide as a hydrogen acceptor.

Enhancing Activity for the Oxygen Evolution Reaction: The Beneficial Interaction of Gold with Manganese and Cobalt Oxides

Abstract: Electrochemical production of hydrogen, facilitated in electrolyzers, holds great promise for energy storage and solar fuel production. A bottleneck in the process is the catalysis of the oxygen evolution reaction, involving the transfer of four electrons. The challenge is that the binding energies of all reaction intermediates cannot be optimized individually. However, experimental investigations have shown that drastic improvements can be realized for manganese and cobalt-based oxides if gold is added to the surface or used as substrate. We propose an explanation for these enhancements based on a hydrogen acceptor concept. This concept comprises a stabilization of an *OOH intermediate, which effectively lowers the potential needed for breaking bonds to the surface. On this basis, we investigate the interactions between the oxides and gold by using DFT calculations. The results suggest that the oxygen evolution reaction overpotential decreases by 100–300 mV for manganese oxides and 100 mV for cobalt oxides.

Linear scaling relationships and volcano plots in homogeneous catalysis – revisiting the Suzuki reaction

Abstract: Linear free energy scaling relationships and volcano plots are common tools used to identify potential heterogeneous catalysts for myriad applications Despite the striking simplicity and predictive power of volcano plots, they remain unknown in homogeneous catalysis Here, we construct volcano plots to analyze a prototypical reaction from homogeneous catalysis, the Suzuki cross-coupling of olefins Volcano plots succeed both in discriminating amongst different catalysts and reproducing experimentally known trends, which serves as validation of the model for this proof-of-principle example These findings indicate that the combination of linear scaling relationships and volcano plots could serve as a valuable methodology for identifying homogeneous catalysts possessing a desired activity through a priori computational screening

Revisiting the Redox Properties of Hydrous Iridium Oxide Films in the Context of Oxygen Evolution

Abstract: The electrochemistry of hydrous iridium oxide films (HIROF) is revisited. Cyclic voltammograms of HIROFs display two reversible redox couples commonly assigned to the Ir(III)/Ir(IV) and Ir(IV)/Ir(V) transitions, respectively. However, compared to the first, the second redox couple has significantly less charge associated to it. This effect is interpreted as partial oxidation of Ir(IV) as limited by nearest neighbor repulsion of resulting Ir(V) sites. Thus, the redox process is divided into two steps: one preceding and one overlapping the oxygen evolution reaction (OER). Here, the ``super-nernstian'' pH dependence of the redox processes in the HIROF is used to expose how pH controls the overpotential for oxygen evolution, as evidenced by the complementary increased formation of Ir(V) oxide. A recently formulated binuclear mechanism for the OER is employed to illustrate how hydrogen bonding may suppress the OER, thus implicitly favoring Ir(V) oxide formation above the thermodynamic onset potential for the OER at low pH.

Nickel–Iron Oxyhydroxide Oxygen-Evolution Electrocatalysts: The Role of Intentional and Incidental Iron Incorporation

Abstract: Fe plays a critical, but not yet understood, role in enhancing the activity of the Ni-based oxygen evolution reaction (OER) electrocatalysts. We report electrochemical, in situ electrical, photoelectron spectroscopy, and X-ray diffraction measurements on Ni1–xFex(OH)2/Ni1–xFexOOH thin films to investigate the changes in electronic properties, OER activity, and structure as a result of Fe inclusion. We developed a simple method for purification of KOH electrolyte that uses precipitated bulk Ni(OH)2 to absorb Fe impurities. Cyclic voltammetry on rigorously Fe-free Ni(OH)2/NiOOH reveals new Ni redox features and no significant OER current until >400 mV overpotential, different from previous reports which were likely affected by Fe impurities. We show through controlled crystallization that β-NiOOH is less active for OER than the disordered γ-NiOOH starting material and that previous reports of increased activity for β-NiOOH are due to incorporation of Fe-impurities during the crystallization process. Through...

Insight on Tafel slopes from a microkinetic analysis of aqueous electrocatalysis for energy conversion.

Abstract: Microkinetic analyses of aqueous electrochemistry involving gaseous H2 or O2, i.e., hydrogen evolution reaction (HER), hydrogen oxidation reaction (HOR), oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), are revisited. The Tafel slopes used to evaluate the rate determining steps generally assume extreme coverage of the adsorbed species (θ ≈ 0 or ≈1), although, in practice, the slopes are coverage-dependent. We conducted detailed kinetic analyses describing the coverage-dependent Tafel slopes for the aforementioned reactions. Our careful analyses provide a general benchmark for experimentally observed Tafel slopes that can be assigned to specific rate determining steps. The Tafel analysis is a powerful tool for discussing the rate determining steps involved in electrocatalysis, but our study also demonstrated that overly simplified assumptions led to an inaccurate description of the surface electrocatalysis. Additionally, in many studies, Tafel analyses have been performed in conjunction with the Butler-Volmer equation, where its applicability regarding only electron transfer kinetics is often overlooked. Based on the derived kinetic description of the HER/HOR as an example, the limitation of Butler-Volmer expression in electrocatalysis is also discussed in this report.

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Understanding Catalytic Activity Trends in the Oxygen Reduction Reaction.

Abstract: Despite the dedicated search for novel catalysts for fuel cell applications, the intrinsic oxygen reduction reaction (ORR) activity of materials has not improved significantly over the past decade. Here, we review the role of theory in understanding the ORR mechanism and highlight the descriptor-based approaches that have been used to identify catalysts with increased activity. Specifically, by showing that the performance of the commonly studied materials (e.g., metals, alloys, carbons, etc.) is limited by unfavorable scaling relationships (for binding energies of reaction intermediates), we present a number of alternative strategies that may lead to the design and discovery of more promising materials for ORR.