Spectroscopic insights into cobalt-catalyzed Fischer-Tropsch synthesis:a review of the carbon monoxide interaction with single crystalline surfaces of cobalt

Abstract

\u3cp\u3eThe present article summarizes experimental findings of the interaction of CO with single crystal surfaces of cobalt. We first provide a quantitative study of non-dissociative CO adsorption on Co(0001) and establish a quantitative correlation between θ\u3csub\u3eCO\u3c/sub\u3e and adsorption site occupation. In light of these findings we revisit the structure of previously reported ordered CO/Co(0001) adsorbate layers. Measurements of the CO coverage at equilibrium conditions are used to derive a phase diagram for CO on Co(0001). For low temperature Fischer-Tropsch synthesis conditions the CO coverage is predicted to be ≈0.5 ML, a value that hardly changes with p\u3csub\u3eCO\u3c/sub\u3e. The CO desorption temperature found in temperature programmed desorption is practically structure-independent, despite structure-dependent heats of adsorption reported in the literature. This mismatch is attributed to a structure-dependent pre-exponential factor for desorption. IR spectra reported throughout this study provide a reference point for IR studies on cobalt catalysts. Results for CO adsorbed on flat and defect-rich Co surfaces as well as particular, CO adsorbed on top sites, and in addition affect the distribution of CO\u3csub\u3ead\u3c/sub\u3e over the various possible adsorption sites.\u3c/p\u3