Owing to the increasing emissions of carbon dioxide (CO2), human life and the ecological environment have been affected by global warming and climate changes. To mitigate the concentration of CO2 in the atmosphere various strategies have been implemented such as separation, storage, and utilization of CO2. Although it has been explored for many years, hydrogenation reaction, an important representative among chemical conversions of CO2, offers challenging opportunities for sustainable development in energy and the environment. Indeed, the hydrogenation of CO2 not only reduces the increasing CO2 buildup but also produces fuels and chemicals. In this critical review we discuss recent developments in this area, with emphases on catalytic reactivity, reactor innovation, and reaction mechanism. We also provide an overview regarding the challenges and opportunities for future research in the field (319 references).

Recent advances in catalytic hydrogenation of carbon dioxide

In this review the phenomenon of proton conductivity in materials and the elements of proton conduction mechanismsproton transfer, structural reorganization and diffusional motion of extended moietiesare discussed with special emphasis on proton chemistry. This is characterized by a strong proton localization within the valence electron density of electronegative species (e.g., oxygen, nitrogen) and self-localization effects due to solvent interactions which allows for significant proton diffusivities only when assisted by the dynamics of the proton environment in Grotthuss and vehicle type mechanisms. In systems with high proton density, proton/proton interactions lead to proton ordering below first-order phase transition rather than to coherent proton transfers along extended hydrogen-bond chains as is frequently suggested in textbooks of physical chemistry. There is no indication for significant proton tunneling in fast proton conduction phenomena for which almost barrierless proton transfer is suggest...

Proton Conductivity: Materials and Applications

On the basis of different types of experiments, the authors develop implicitly the model of surface-enhanced Raman scattering (SERS) of adsorbates on metal surfaces. The long-range enhancement by resonances of the macroscopic laser and Stokes field is separated quantitatively from the metal electron-mediated resonance Raman effect. The latter mechanism proceeds by increased electron-photon coupling at an atomically rough surface and by temporary charge transfer to orbitals of the adsorbates. This model can account for the chemical specificity and vibrational selectivity of SERS and (partly) for the SERS specificity of the various metals.

https://iopscience.iop.org/article/10.1088/0953-8984/4/5/001/pdf

Surface-enhanced Raman scattering

Traditional physicochemical and biological techniques, as well as advanced oxidation processes (AOPs), are often inadequate, ineffective, or expensive for industrial water reclamation. Within this context, the electrochemical technologies have found a niche where they can become dominant in the near future, especially for the abatement of biorefractory substances. In this critical review, some of the most promising electrochemical tools for the treatment of wastewater contaminated by organic pollutants are discussed in detail with the following goals: (1) to present the fundamental aspects of the selected processes; (2) to discuss the effect of both the main operating parameters and the reactor design on their performance; (3) to critically evaluate their advantages and disadvantages; and (4) to forecast the prospect of their utilization on an applicable scale by identifying the key points to be further investigated. The review is focused on the direct electrochemical oxidation, the indirect electrochemical oxidation mediated by electrogenerated active chlorine, and the coupling between anodic and cathodic processes. The last part of the review is devoted to the critical assessment of the reactors that can be used to put these technologies into practice.

Single and Coupled Electrochemical Processes and Reactors for the Abatement of Organic Water Pollutants: A Critical Review.

Progress in material selection for solid oxide fuel cell technology: A review

THE catalytic activity and selectivity of metals can be altered dramatically and reversibly by supplying or removing oxide anions, O2–, at the metal catalyst surface by interfacing the catalyst with an O2– conductor such as zirconia1–6. This effect, termed non-faradaic electrochemical modification of catalytic activity (NEMCA), leads to a steady-state catalytic reaction rate increase up to 3 × 105 times higher than the rate of supply or removal of O2– at the catalyst surface1,3,4. Here we report that β"-Al2O3, which is a Na+ conductor, can also induce the NEMCA effect. Furthermore we show that the origin of the NEMCA effect lies in the controlled variation of catalyst work function on polarization of the metal-solid-electrolyte interface, and demonstrate that the rates of metal-catalysed reactions depend exponentially on the average catalyst work function. Thus the influence of catalyst electronic structure, rather than surface geometry, is here the key factor in catalytic activity.

Dependence of catalytic rates on catalyst work function

Non-faradaic electrochemical modification of catalytic activity: A status report

Non-faradaic electrochemical modification of catalytic activity: 1. The case of ethylene oxidation on Pt

It was found that catalytic activity and selectivity of metal catalysts can be altered dramatically and in a reversible manner. This is accomplished by electrochemically supplying oxygen anions onto catalytic surfaces via polarized solid electrolyte cells. Oxygen anions, forced electrochemically to adsorb on the catalyst surface, alter the catalyst work function in a predictable way and lead to reaction rate increases of the order of 1500%. Changes in catalytic reaction rates typically exceed the rate of O/sup 2 -/ transport to or from the catalyst surface by 10/sup 2/-10/sup 4/. The case of several catalytic reactions in which this new phenomenon has been observed is discussed.

Non-faradaic electrochemical modification of catalytic activity

X-ray photoelectron spectroscopy (XPS) was used to investigate the effect of electrochemical oxygen pumping on Pt catalyst films interfaced with an O 2 -conducting yttria-stabilized zirconia solid electrolyte. It was found that electrochemical oxygen pumping to the catalyst causes spillover of significant amounts of anionic oxygen from the solid electrolyte onto the platinum film surface. The spillover oxygen species has an XPS binding energy 528.8 eV compared to 530.4 eV for chemisorbed oxygen, which is also observed on the surface, and is less reactive than chemisorbed oxygen with the reducing ultrahigh vacuum background. The detection of the anionic oxygen species upon electrochemical pumping confirms the previously proposed explanation of the non-Faradaic electrochemical modification of catalytic activity (NEMCA) or electrochemical in catalysis

Symeon Bebelis

Papers

Dependence of catalytic rates on catalyst work function

Non-faradaic electrochemical modification of catalytic activity: A status report

Non-faradaic electrochemical modification of catalytic activity: 1. The case of ethylene oxidation on Pt

Non-faradaic electrochemical modification of catalytic activity

Origin of non-faradaic electrochemical modification of catalytic activity