Proton–hydride tautomerism in hydrogen evolution catalysis

Efficient generation of hydrogen from renewable resources requires development of catalysts that avoid deep wells and high barriers. Information about the energy landscape for H_2 production can be obtained by chemical characterization of catalytic intermediates, but few have been observed to date. We have isolated and characterized a key intermediate in 2e^– + 2H^+ → H_2 catalysis. This intermediate, obtained by treatment of Cp*Rh(bpy) (Cp*, η^5-pentamethylcyclopentadienyl; bpy, κ^2-2,2′-bipyridyl) with acid, is not a hydride species but rather, bears [η^4-Cp*H] as a ligand. Delivery of a second proton to this species leads to evolution of H_2 and reformation of η^5-Cp* bound to rhodium(III). With suitable choices of acids and bases, the Cp*Rh(bpy) complex catalyzes facile and reversible interconversion of H^+ and H_2

Pope Farm Expansion Project

Final project for INAG 248: Topics in Sustainable Agriculture (Spring 2021). University of Maryland, College Park.The group of students provided recommendations to M-NCPPC Montgomery County Parks by planting diverse types of vegetables and other crops that will benefit the community in growing familiar crops which they will be able to use appropriately and be able to feed their families while considering the harvesting and transportation of these foods to the people in the Pope Farm and creating the outline of the vegetable crops that the team recommends.Montgomery County Parks (MoCo

Unique separator-spectrometer experiments at the frontiers of nuclear physics: the Super-FRS scientific program

The superconducting fragment separator (Super-FRS) is the magnetic high-resolution spectrometer, which will be coupled to the heavy-ion synchrotron complex at the future Facility for Antiproton and Ion Research FAIR. It will enable a variety of unique nuclear physics experiments. Key examples of the experimental program are presented, for instance the production and study of exotic hypernuclei (i.e.: nuclei far-off stability containing hyperons), the production and study of mesic atoms (i.e.: atoms containing bound mesons, like pions or eta mesons), the discovery of new neutron-rich isotopes, the search for new phenomena in weakly bound or dilute nuclear systems, and the search for neutron radioactivity, an elementary radioactive decay mode, which has not been discovered yet

DFT study of an unusual proton-relay role for Cp* in hydrogen evolution catalysis

Understanding mechanisms of the hydrogen evolution reaction (HER) is crucial to designing efficient catalysts for the prodn. of solar fuels. Cp*Rh(bpy) (Cp* = η^5- pentamethylcyclopentadienyl; bpy = κ^2-2,2'- bipyridyl) generates hydrogen in the presence of acid. However, the nature of the elementary steps leading to H-H formation has not been clear, as chem. characterization of intermediates in the catalytic reaction has been difficult to obtain. Here, we present a joint exptl.- computational study that addresses this challenge. D. functional theory (DFT) calcns. demonstrate that the catalyst first undergoes a 2e- redn. to form a Rh^I complex. Subsequently, in presence of acid, the Rh complex undergoes protonation at the Cp* ligand to form a complex bearing an [η^4-Cp*H] ligand, preserving the RhI center. DFT calcns. show that this complex is 6.8 kcal /mol more stable than the analogous Rh^(III) hydride. Following the formation of this intermediate, a second protonation can be carried out which results in evolution of hydrogen and restoration of η^5-Cp*. To the best of our knowledge, these results are among the first to show Cp* can serve as a proton relay in HER. New DFT results on the full mechanism for this compd. will be presented, and predictions of possible improvements to the catalyst will be discussed in light of the newly characterized intermediate