Photocatalysis can directly store solar energy in the form of chemical fuels such as green hydrogen from water splitting, but its need for pure water limits its commercial viability, particularly in regions facing water scarcity. Even small amounts of contaminants in the feedstock can severely reduce the lifetime and performance of photocatalytic systems, and most feasibility analysis often underestimate the cost of purified water and its transportation which can be as high as $45 per tonne in some regions. Aside from economic concerns, the use of pure water for hydrogen production may add further strain on the water supply chain. The frequency and severity of droughts worldwide is expected to increase due to anthropogenic climate change, and even a drought was declared in a majority of areas in England by the Environment Agency in 2022. Land available for industrial development is also becoming increasingly limited due to competing utilization for agricultural, commercial and residential purposes. Rising global populations, competing land use and increasing concerns over water and land scarcity justifies an urgent need to consider a shift towards alternative water sources for fuels production. The utilization of untreated water sources such as seawater to drive photocatalytic reactions is increasingly reported, but the performance and long-term stability of these systems are low and reengineering of the co-catalysts was often required for the systems to work under such conditions. Therefore, the viability for practical applications has remained questionable. Alternatively, using water vapour from untreated water may help to avoid issues such as photocatalyst poisoning and the scattering, reflection and absorption of sunlight by contaminants in the water. Vapour-phase photocatalytic or electrolysis processes have a lower energy requirement for splitting water due to the lower standard Gibbs free energy of formation of gaseous water compared to liquid water (ΔG 0 [H 2 O(g)]= -228.6 versus -237.2 kJ mol -1 [H 2 O(l)]). Furthermore, vapour-phase reactions have decreased mass transfer resistance and promote the rapid desorption of evolved H2 and O2 gases, which inhibits back reactions and reduces light scattering. However, vapour-phase water splitting systems require complex microreactors consisting of numerous microchannels for proper gas distribution. This, coupled with the energy-intensive production of water vapour, largely negates the potential advantage of vapour-phase water splitting. Sunlight can be an alternative green energy source to generate water vapour via photothermal conversion devices such as solar vapour generators (SVG), which can convert most of the solar spectrum to thermal energy in order to heat water at the liquid-vapour interface. Such devices offer a cost-effective alternative to other water desalination and purification technologies. Carbon-based materials are often used as solar absorbers due to their low cost, ease-of-fabrication and broad-spectrum solar absorption. Conversely, most photocatalytic water splitting systems can only use high-energy photons to drive the reaction leaving a large portion of the solar spectrum, particularly the long-wavelength visible (Vis) and infrared regions (IR), unutilized. Hence, combining these two solar conversion technologies could provide a light management strategy for the full utilization of the solar spectrum.