Moderate Electron Doping Assists in Dissociating Water on a Transition Metal Oxide Surface (n-SrTiO3)

March 12, 2023

Water dissociation on transition metal oxide (TMO) surfaces regulates their catalytic activity in aqueous media. Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) has differentiated TMO surfaces by the population of their first hydration layer on a scale between water molecularly absorbed and water fully dissociated into hydroxyl groups. Here, we show that electron-doping a single TMO (SrTiO3: STO) can also span this range, with the data on lightly (0.1 wt % Nb) and moderately (0.7 wt % Nb) doped STO suggestive of partial and full water dissociation, respectively.

Coherent Acoustic Interferometry during the Photodriven Oxygen Evolution Reaction Associates Strain Fields with the Reactive Oxygen Intermediate (Ti–OH*)

Oct. 4, 2021

The oxygen evolution reaction (OER) from water requires the formation of metastable, reactive oxygen intermediates to enable oxygen–oxygen bond formation. Conversely, such reactive intermediates could also structurally modify the catalyst. A descriptor for the overall catalytic activity, the first electron and proton transfer OER intermediate from water, (M–OH*), has been associated with significant distortions of the metal–oxygen bonds upon charge-trapping. Time-resolved spectroscopy of in situ, photodriven OER on transition metal oxide surfaces has characterized M–OH* for the charge trapping and the symmetry of the lattice distortions by optical and vibrational transitions, respectively, but had yet to detect an interfacial strain field arising from a surface coverage of M–OH*.

One-Electron Water Oxidation Intermediate on TiO2 P25 Probed by Ultrafast Attenuated Total Reflection

Oct. 4, 2021

Water oxidation is considered as one of the most important reactions in solar-to-fuel generation. The initial catalytic intermediates formed on an ultrafast timescale play a great role in controlling water oxidation reaction. Here, we use ultrafast in situ infrared attenuated total reflectance spectroscopy to study the initial water oxidation intermediates at a state-of-the-art TiO2 P25/aqueous interface.

The electron-transfer intermediates of the oxygen evolution reaction (OER) as polarons by in-situ spectroscopy

April 26, 2021

The conversion of diffusive forms of energy (electrical and light) into short, compact chemical bonds by catalytic reactions regularly involves moving a carrier (electron or hole) from an environment that favors delocalization to one that favors localization. While delocalization lowers the energy of the carrier through its kinetic energy, localization creates a polarization around the carrier that traps it in a potential energy minimum. The trapped carrier and its local distortion—termed a polaron in solids—can play a role as a highly reactive intermediate within energy-storing catalytic reactions but is rarely discussed as such. Here, we present this perspective of the polaron as a catalytic intermediate through recent in-situ and time-resolved spectroscopic investigations of photo-triggered electrochemical reactions at material surfaces.

Free energy difference to create the M-OH* of the oxygen evolution reaction by time-resolved optical spectroscopy

April 19, 2021

Theoretical descriptors differentiate the catalytic activity of materials for the oxygen evolution reaction (OER) by the strength of oxygen binding in the reactive intermediate created upon electron transfer. Recently time-resolved spectroscopy of (photo)-electrochemically driven OER followed the vibrational and optical spectra of this intermediate, denoted M-OH*. However, these inherently kinetic experiments have not been connected to the relevant thermodynamic quantities. Here, we discover that picosecond optical spectra of the Ti-OH* population on lightly doped SrTiO3 are ordered by the surface hydroxylation.

Accuracy in Resolving the First Hydration Layer on a Transition-Metal Oxide Surface: Experiment (AP-XPS) and Theory

Oct. 25, 2020

Understanding the equilibrium conditions at the metal oxide/aqueous interface is a key component toward visualizing the structure of water in confined environments and differentiating the catalytic activity of transition-metal oxides. While ambient pressure X-ray photoelectron spectroscopy (AP-XPS) has been the primary technique to investigate the formation of a hydration layer on many surfaces, results over the extended relative humidity (RH) range accessible experimentally have not been compared quantitatively to theoretical predictions. With the use of first-principles theoretical methods and accumulated knowledge of AP-XPS spectral analysis, we do so here for a model surface, TiO2-terminated undoped SrTiO3(100) (STO).

The JPC Periodic Table

Feb. 13, 2020

In this Virtual Issue, we celebrate the International Year of the Periodic Table by presenting one paper in JPC that is concerned with each of the 118 elements.

Charting a Course for Chemistry

Feb. 13, 2020

To mark the occasion of Nature Chemistry turning 10 years old, we asked scientists working in different areas of chemistry to tell us what they thought the most exciting, interesting or challenging aspects related to the development of their main field of research will be — here is what they said.

Selecting between two transition states by which water oxidation intermediates on an oxide surface decay

July 18, 2019

While catalytic mechanisms on electrode surfaces have been proposed for decades, the pathways by which the product’s chemical bonds evolve from the initial charge-trapping intermediates have not been resolved in time. Here, we discover a reactive intermediate population with states in the middle of a semiconductor’s band-gap to reveal the dynamics of two parallel transition state pathways for their decay.

Probing Electric Double Layer Composition via in-situ Vibrational Spectroscopy and Molecular Simulations

July 18, 2019

The EDL guides electrode passivation in batteries, while in (super)capacitors, it determines charge storage capacity. Despite its importance, quantification of the nanometer-scale and potential-dependent EDL remains a challenging problem. Here, we directly probe changes in the EDL composition with potential using in-situ vibrational spectroscopy and molecular dynamics simulations for a Li-ion battery electrolyte (LiClO4 in dimethyl carbonate).