Fig. 6

a Homogeneous catalysts for the reduction of carbon dioxide. (left) Mn(bpy-tBu)(CO)₃Br and (right) Iron 5,10,15,20-tetrakis(2′,6′-dihydroxylphenyl)-porphyrin. Adapted with permission from ref [61] and [62]. Copyright 2013, ACS publications and 2013 RSC Publishing, respectively. b Morphology of concave RD nanoparticles. SEM image (left) and the corresponding model (right). Adapted with permission from ref [70]. Copyright 2015, ACS publications. c Mechanistic model for the reduction of carbon dioxide to carbon monoxide on polycrystalline Au and oxide-derived Au. Adapted with permission from ref [72]. Copyright 2012, ACS publications