Tuning the RWGS Reaction via EPOC and In Situ Electro-oxidation\nof Cobalt Nanoparticles

Abstract

The\nelectrochemical promotion of catalytic activity by non-noble\ntransition metals is rarely reported in the literature. Here, Co nanoparticles\nwere utilized for the electrochemical activation of CO₂ hydrogenation under atmospheric pressure conditions. A range of\ntransient kinetic experiments in conjunction with X-ray photoelectron\nspectroscopy and imaging techniques were employed to correlate the\nobserved catalytic activity with the electronic and morphological\ncharacteristics of the cobalt catalyst surface. Our results show that\nmigrating ions from the solid electrolyte to the catalyst surface\nhas a dual effect, which has an impact on the observed catalytic behavior.\nFirst, they lead to an electrochemically formed double layer on the\ncatalyst surface, which effectively modifies the catalyst work function\nand consequently alters the observed catalytic rate. Second, they\nhave a profound effect on the oxidation state of cobalt and therefore\non the structure of the cobalt oxide particles formed. The presence\nof Co oxide phases upon anodic polarization shows up to a 5-fold increase\nin the catalytic rate of the reverse water gas shift (RWGS) reaction.\nThe enhancement of the catalytic activity observed in this work, with\na relatively inexpensive cobalt oxide film, is comparable to that\nobtained with noble metal catalysts in classical EPOC studies. The\npresent study also demonstrates that the formation of different oxide\nphases can be controlled accurately by electrochemical means and used\nto tune the catalytic activity and selectivity of cobalt. The reported\nresults could guide the design and operation of more selective and\nactive catalytic processes for the RWGS reaction.