To produce solar fuels from CO₂ photoreduction with water, TiO₂ is most frequently studied as it is inexpensive, earth-abundant, and chemically stable. But the darwbacks of using TiO₂ include low light absorption in the visible range, low CO₂ adsorption capability, and fast charge recombination. We have developed many strategies to improve the catalytic performance of TiO₂ through surface engineering, and one recent approach is to coat an ultrathin overlayer of metal oxide (e.g. Al₂O₃ or MgO) on TiO₂ photocatalyst though atomic layer deposition (ALD). In one experiment, we found coating an ultrathin Al₂O₃ on TiO₂ nanorods with 5 ALD cycles led to significant improvement, mainly because of the surface passivation by ALD overlayer and resultant reduced surface recombination. In another experiment, we found coating an ultrathin MgO overlyaer on porous TiO₂ with 5 cycles of ALD layers led to even more significant enhancement in CO₂ photoreduction. The changes of surface properties in correlation with the ALD coating layer thickness as well as the photocatalytic performances were investigated.