Highly Efficient Conversion of CO₂ to CH₃OH through Photoreduction over WO₃ Catalyst Using a Highly Concentrated CO₂ Solution with Ammonium Bicarbonate

The photoreduction of CO2 was performed in an aqueous solution using tungsten trioxide (WO3) as the catalyst. The reaction was performed using an aqueous ammonium bicarbonate solution with approximately 60 times the normal CO2 concentration in an aqueous solution without ammonium bicarbonate. Owing to the high CO2 concentration in the aqueous solution, the photoreduction of CO2 over the WO3 catalyst proceeded efficiently. In the first 1 h of CO2 photoreduction, approximately 100 ppm of CH3OH was produced, which corresponds to 0.03 mmol/g. The produced CH3OH was adsorbed onto the WO3. However, CH3OH adsorption on WO3 had little effect on the photoreduction of CO2 in this experimental system.