Recent progress in photothermal catalyst design for methanol production

Methanol is used as a feedstock to produce various commodity chemicals and as a fuel in the transport sector. However, current methanol production methods are unsustainable as they use fossil fuels as both a feedstock and an energy source. In recent years, methanol production from CO2 and H2 has attracted a lot of attention, allowing the valorisation of CO2. Traditionally, CO2 to CH3OH conversions have relied on thermocatalytic processes with high pressures (> 5 MPa) and temperatures (220–300 °C) needed to achieve reasonable rates and a high methanol selectivity. With a view towards minimizing energy-inputs, researchers are now actively seeking photothermal catalysts that convert solar energy into heat to achieve the optimal reaction temperatures required for CO2 hydrogenation to CH3OH. A number of promising catalysts have been discovered for photothermal CO2 hydrogenation, such as defective In2O3-based catalysts, offering high methanol selectivity at ambient pressures. However, overall photothermal catalytic production rates of methanol remain modest compared to thermochemical catalysis routes, which can mainly be attributed to (1) modest light-to-heat conversion by the photothermal catalysts, and (2) reactor design challenges at large-scales. This review summarizes recent progress in this exciting field, whilst also exploring strategies that may allow higher CO2 conversion rates and higher CH3OH yields in the future.