Utilization factor, atom-based

An understanding of the factors that influence the rates of hydrogen atom abstraction processes is very important in order to maximize the utility of radical-based processes in carbon-carbon bond-forming reactions. This is because most such reactions are chain reactions in which one of the key propagation steps involves transfer of a hydrogen atom from some hydrogen atom transfer agent, such as tri-n-butyltin hydride. 

Atom-Based Utilization Factor at the Level of Pt Nanoparticles... 

The catalyst layers evaluated in this model-based analysis are not intended to represent the best-in-class in terms of performance. Instead, the experimental studies were picked out from the literature because they provided porosimetry as well as performance data. Nevertheless, the low value of the CL effectiveness factor is a striking result of this analysis. The value of Fcl decreases from 4 % at jo < 0.4 A cm to 1 % aty o 1 A cm . This parameter incorporates statistical effects and transport phenomena across all scales in the CCL. The values found are consistent with an experimental evaluation of effectiveness factors by Lee et al. (2010) if the values found in that study are corrected with the atom utilization factor F p, the agreement is very good. The low value of Fcl suggests that tremendous improvements in fuel cell performance and Pt loading reduction could be achievable through advanced structural design of catalyst layers. 

With the above-mentioned new developments, theoretical calculations should be able to use more realistic models of elementary reactions and homogeneous catalysts and utilize many important aspects of transition-metal-catalyzed reactions, including the role of different ligands, the role of different transition-metal atoms, chemo-, and stereoselectivity, and other factors controlling the reactions. Predictions of catalytic reactivities based on theoretical calculations should be forthcoming. Collaboration between experimentalists and theoreticians is strongly encouraged. 

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