Abstract
One of the many contributions of Harold Winters to surface science was his pioneering ultrahigh vacuum study on the kinetics of the technologically important dissociation of CH4 on transition metals in the 1970s. He observed a dramatic activation of the dissociation with surface temperature alone and a huge isotope effect and suggested a simple dynamical model to rationalize his results. Since that time, our general understanding of the dynamics of gas-surface dissociations has exploded due to experimental advances (e.g., molecular beam and eigenstate resolved studies) and theoretical advances (quantum or classical dynamics on ab initio potential energy surfaces). This review tries to highlight how our understanding of the dynamics of CH4 dissociation on transition metals has matured since Harold's pioneering experiments and original model.
Highlights
Harold Winters is best known for his many and various contributions to surface science related to plasma–surface interactions, he pioneered studies of activated adsorption of CH4 on transition metal surfaces in the mid 1970s
Harold performed the first study of this activated dissociation on an atomically clean transition metal in the early days of clean UHV surface science and suggested a simple dynamical model to rationalize his results
Far more detailed information on the dissociation dynamics is available from molecular beam experiments than kinetic studies since these unravel some of the thermal averaging inherent in the kinetics
Summary
Harold Winters is best known for his many and various contributions to surface science related to plasma–surface interactions, he pioneered studies of activated adsorption of CH4 on transition metal surfaces in the mid 1970s This had long been a subject of intense interest, even predating the advent of clean surface science, because of its central role in the steam reforming of natural gas to produce syngas, principally a mixture of H2 þ CO. Since the thermal rate for this dissociation is quite low, there is a high barrier to this process and energy must be supplied to affect this dissociation This has traditionally been discussed in terms of so-called “C–H bond activation.”. This has traditionally been discussed in terms of so-called “C–H bond activation.” Harold performed the first study of this activated dissociation on an atomically clean transition metal in the early days of clean UHV surface science and suggested a simple dynamical model to rationalize his results.
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