The CO2 transformation via electrochemical reduction has been a longstanding target, considering the application of intermitted renewable energy sources. In such a system, the ability of producing liquid fuels is highly desirable due to their high energy density and security in storage and transportation, to which the design of electrocatalytic materials is the main focus. In this direction, Copper-based materials showed great promise to promote selective electroreduction of CO₂ to C₂₊ products with a high conversion efficiency. Research efforts have been made to improve the activity and selectivity of Cu-based electrocatalysts through doping or alloying with other transition metals. Moreover, these electrocatalysts can be coupled to semiconductors to obtain photocathodes. Cuprite (Cu2O) thin films are currently among the most studied p-type semiconductors employed to this aim, however it suffers from severe photo-corrosion and requires multi-step passivation approaches. Generally,  the fine tuning of catalytic properties and selectivity towards the desired products requires an exhausting trial and effort approach, currently representing  the main bottleneck in the realization of performative electrodes.

In the present study Cu-Ti and Cu-Sn alloys are studied for the electro- and photo-electrocatalytic reduction of CO2 (CO2RR) [1][2]. The role of Titanium and Tin relative amount in Cu-based alloys was analyzed in a high-throughput approach. To this aim, lateral concentration gradients of Ti and Sn in copper thin films were prepared by magnetron co-sputtering, producing an entire materials library in a single sample. On the other hand, the  local electrochemical response of limited portion of the sample (about 1mm²), corresponding to a defined atomic ratio, was measured with a scanning flow (photo)electro-chemical cell. High  throughput synthesis and characterization of a materials library, in fact, allowed to drastically reduce experimental effort to find the best configuration. In such a way, it was possible to rapidly select the best atomic concentration for each electrode in terms of electrochemical characteristics ( 5 at.% of titanium and 10 at.% of tin in CuTi and CuSn, respectively). Once the best atomic concentration was obtained, a selectivity analysis has been carried with an HPLC and micro GC in order to reveal, during the CO2 reduction reaction, both the liquid and the gaseous products, respectively.

In addition to that, those catalysts were coupled with a semiconductor, in particular electrodeposited Cu2O electrodes with different passivation layers (TiO2 and AZO), to study their stability and performance under both light and dark configurations.