The opportunities and challenges for exploiting the production of syngas from the electrochemical reduction of CO ₂ are critically reviewed and analysed.

Methane can directly be transformed into liquid C₁ oxygenated products with selectivities above 95% at 13% conversion by deep UV photocatalysis, in the presence of H₂O and air. Pure silica zeolites, and more specifically, beta zeolite with a large number of internal silanol groups is active and selective, while amorphous silica with no micropores is much less efficient. Irradiation produces the homolytic cleavage of surface hydroxyl groups, leading to silyloxyl radicals that will generate methyl radicals from methane. The selectivity arises from the occurrence of the reaction in a confined space restricting the mobility of the radical intermediates that will be mostly attached to the solid surface. Energy consumption of the process is in the order of 7.2 Gcal × mol^–1 that compares very favorably with the energy required for transforming methane to synthesis gas (15.96 Gcal × mol^–1).

Gold nanoparticles supported on P25 TiO₂ act as highly efficient photocatalysts for promoting the simultaneous H₂O reduction to H₂ and CO oxidation to CO₂. This photocatalytic process can be performed using simulated solar light as well as light from a LED quasi monochromatic centred at 450 nm, indicating that not only UV but also visible light promotes the reaction. This novel photocatalytic reaction corresponds to the water gas shift which is an endothermic process that is currently carried out on a large industrial scale at temperatures about 350 °C. In contrast, the photocatalytic process is performed at ambient temperature with no other energy requirement than sunlight. Other related TiO₂ and CeO₂ photocatalysts containing noble metals (Pt or Pd) behave similarly, but with lower efficiency both in the UV and in the visible region than Au/TiO₂.