From a quantitative point of view, previously reported NH3 production rates of pure g-C3N4 or of heterojunctions including g-C3N4, are higher than those obtained here. However, it is important to stress a delicate point related to the method employed to measure the photogenerated NH3. Currently, most of the reports about ammonia production by nitrogen fixation make use of colorimetric methods which are known to be possibly affected by several interfering compounds, in particular in presence of a sacrificial agent (which should be removed according to ref.