Artificial photosynthesis is an up to date topic for the fixation of CO2 in form of valua-ble fuels. Recently, we set up an innovative concept of photoreactor to be applied to CO2 photoreduction, enabling operation up to 20 bar. This allows to improve CO2 sol-ubility and to explore unconventional operating conditions for this very challenging reaction. Following a preliminary communication, to demonstrate the validity of the ap-proach systematic testing has been here carried out on different TiO2 photocatalysts (anatase, rutile and anatase+rutile) doped with 0.1 wt% Au, by tuning pressure, tem-perature and pH. The operating conditions have been selected to maximise the pro-duction of gas phase products, i.e. CH4 + H2, with respect to liquid phase organic com-pounds. The present results overperform many of the recent achievements reported in the literature and throw the basis for a further optimisation of the photocatalytic materi-al and of the photoreactor.