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Closing the carbon cycle and enabling a carbon circular economy in energy intensive industries (iron and steel, cement, refineries, petrochemistry and fertilizers) are topics of increasing interest to meet the demanding target of defossilizing the production. The focus of this perspective contribution is on CO2reuse technologies in this context. While this is a topic with abundant literature, the analysis of applying CO2reuse technologies evidences the need to go beyond those receiving most of the attention today, such as conversion of CO2to methanol. Depending on the specific context, different scenarios are expected. Some examples illustrating the search for novel solutions are provided, such as those starting from the efficient conversion of CO2to CO. Once CO is produced from CO2many bio-chemical and catalytic conversion routes open up next to direct uses of CO in the steel and chemical sector.

A solar driven photo-electro-catalytic (PEC) device for CO2 reduction/water oxidation is here presented. The electrodes are engineered to be used in the n-type configuration, without using precious metals or rare/expensive raw materials. Specifically, the photoanode for water oxidation is made of TiO2 nanotube arrays prepared via controlled anodic oxidation, while Cu2O-TiO2 heterostructures, synthesised by ultra-sonicated assisted co-precipitation and then spray-coated over a carbon-based gas diffusion layer (GDL), are used as electrocathode materials for CO2 reduction. All the tests are performed without applying external bias or adding sacrificial donors, in a compact homemade PEC reactor in comparison with a conventional slurry photoreactor. The catalytic performances are evaluated in terms of formic acid and acetic acid production, the latter involving the formation of C-C bond. The effect of the presence of TiO2 is investigated in comparison with a bare cuprous oxide (Cu2O) film. Results for the bare Cu2O/GDL electrode (no TiO2) show 31.8 and 80.6 µmol h-1 gCu-1 as formic acid and acetic acid production rates, respectively. Cu2O-TiO2/GDL electrode, instead, shows more than one order of magnitude higher productivity (0.69 and 2.59 mmol h-1 gCu-1, respectively). The Faradaic efficiency (FE) to acetic acid is much higher for Cu2O-TiO2/GDL electrodes (61.9 %) considering the higher number of electrons involved for acetic acid with respect to formic acid (8 vs. 2). This behaviour can be ascribed to the synergetic electrocatalytic effects of the as-formed Cu2O-TiO2 heterostructures, favouring the formation of C-C bond for the sustainable production of >C1 chemicals and fuels.

The photoelectrocatalytic properties of TiO2 nanotube ordered films (TiNT) could be enhanced by decorating them with graphitic-C3N4. The g-C3N4/TiNT heterojunctions have been successfully prepared using a facile and direct chemical vapor deposition method. By controlling type and amount of utilized nitrogen precursor, it is possible to tune the properties of the resulting nanocomposites. Under light irradiation the photoelectrocatalytic activity of the fabricated g-C3N4/TiNT heterojunctions is about 4.7 times than that of bare TiNT, due to their better separation capability of photogenerated charges and wider optical absorption. Characterization by XRD, XPS, UV-Vis DRS and chronoamperometry under simulated sunlight, evidence the relations between the method of preparation and the features of the samples, revealing the high potential of these nanocomposites.