Solar-Driven Electrochemical Green Fuel Production from CO<sub>2</sub> and Water Using Ti<sub>3</sub>C<sub>2</sub>T<sub>x</sub> MXene-Supported CuZn and NiCo Catalysts

This protocol describes the synthesis and activity mapping of bi-metallic, MXene-supported cathodes for carbon dioxide reduction (CO2R) and anodes for water splitting utilizing solar energy in alkaline media. A reverse current pulse electrodeposition technique was used to control the nanostructure, grain refinement, and alloy composition of the fabricated electrodes. Both anodes and cathodes are noble metal-free and supported on two-dimensional (2D) titanium carbide (Ti3C2Tx) MXene, which reduces contact resistance and facilitates the charge transfer from substrate to reactants via catalysts. Copper zinc (CuZn) supported on Ti3C2Tx MXene are used as cathodes for methanol production in thermocatalytic CO2 conversion, and here we have demonstrated their performance in electrochemical CO2 reduction (CO2R) for the first time. Nickel cobalt (NiCo) supported on Ti3C2Tx MXene are similarly fabricated via pulse electrodeposition and tested as anodes for water electrolysis driven by a solar cell under simplified laboratory conditions. The activity also describes the structural characterization of metallic thin films. Detailed setup for the integration of the state-of-the-art perovskite silicon tandem solar cell with electrochemical cell, which in turn feeds in-line gas chromatography, is demonstrated for both CO2R and water electrolysis (WE). A setup detailing the water electrolysis at commercial conditions of highly caustic alkaline solutions (30% KOH), high temperatures (60 °C), and in a zero-gap cell is demonstrated on the fabricated anode paired with a Pt/C spray-coated cathode.