An analysis of the substances with the catalyst role showed that carbon nitride (C3N4), titania, cadmium sulfide, and molybdenum sulfide are among the most reported catalysts (Figure ). The other catalysts in the top 15 are zinc oxide, Co3O4, tungsten oxide, indium zinc sulfide, Fe2O3, BiVO4, cadmium zinc sulfide, and nickel phosphide. Carbon nitride is a promising photocatalyst due to its visible light absorption, stability in alkaline and acidic conditions, and organic composition. Cadmium sulfide has bandgap and band positions suitable for overall water splitting using visible light irradiation. However, it is unstable due to photocorrosion and the potential for environmental pollution due to the presence of toxic cadmium. Despite these concerns, studies on CdS continue due to hopes of stabilizing it and containing the environmental damage at a later stage. The most reported photocatalysts were also color coded according to their patent-to-journal ratio. In general, oxide photocatalysts such as tungsten trioxide, zinc oxide and titanium dioxide have high contribution from patents, compared to nitride and sulfide photocatalysts. Due to its visible light activity and stability, films of WO3 has been patented for applications such as air purification and refining. In addition, from the pool of 100 photocatalysts with the highest number of publications, we selected 10 catalysts that demonstrated the highest growth within the last five years (Figure ). Carbon nitride stands out from the rest of the catalysts due to its relatively very high number of publications along with rapid growth in recent years. Factors such as band gap suitable for visible light absorption, band positions suitable for overall water splitting, metal-free composition and ease of preparation contribute to the high interest in carbon nitride photocatalysts. Most of the other catalysts with higher number of publications are also growing rapidly, due to the recent interest in finding sustainable alternatives to the existing catalysts. It is also worthwhile to note that titanium dioxide continues to draw interest more than 5 decades after the first report of using it for photocatalytic water splitting. We then analyzed the data to find the reactions which are facilitated using photocatalysts. Figure presents the most reported reactions along with their patent to journal ratios. Photocatalysts are most used for water splitting to produce hydrogen, and for the decomposition of pollutants. The electron-hole pairs generated can be used for carrying out both the reduction and the oxidation reactions, as seen by the presence of both photooxidation and photochemical reduction. Due to the limited availability of photocatalysts capable of performing overall water splitting, a combination of two different photocatalysts each capable of performing only water oxidation or water reduction in a tandem reaction is widely studied. Electrochemical reduction and oxidation are other important reactions in the publications reporting photocatalysts. Electrocatalysts which enhance the hydrogen evolution or oxygen evolution reaction, referred to as co-catalysts, are loaded on to the surface of the photocatalysts. To a lesser extent, photocatalysts are also studied for organic reactions such as regioselective synthesis, 109 and diastereoselective synthesis. Figure shows the cooccurrence between the reactions and the most used catalysts within the photocatalyst dataset. Due to their band positions suitable for hydrogen evolution reaction and low cost, sulfide photocatalysts such as molybdenum disulfide, 111, 112 cadmium sulfide, zinc sulfide, and cadmium zinc sulfide have higher contribution to this reaction type. Despite their favorable properties, stability is a common drawback in the sulfide photocatalysts constraining their success. Sulfide based materials such MoS2 are also widely explored as co-catalysts to enhance the hydrogen evolution properties of stable photocatalysts such as C3N4. Despite its large bandgap capable of absorbing only UV light, ZnO continues to be explored as photocatalysts, due its benign nature and low cost, especially for photocatalytic decomposition of pollutant molecules. The visible light activity of ZnO is increased by doping it with metals, non-metals, and creating heterojunctions 116 with other small bandgap semiconductors. The presence of iron in decomposition and photooxidation studies can be attributed to the use of photo Fenton reaction, which involves iron and hydrogen peroxide, and iron containing metal organic frameworks The presence of iron in decomposition and photooxidation studies can be attributed to the use of photo Fenton reaction, which involves iron and hydrogen peroxide, and iron containing metal organic frameworks 118 for the oxidation of pollutant substances. In the oxygen evolution reaction type, bismuth vanadate and cobalt have high contribution due to their high photocatalytic 120 and co-catalytic 121 activity respectively towards this reaction type. Another catalyst with high contribution is eosin, which has high presence in organic conversion reactions, due to its use as a photosensitizer in these reactions. Figure lists the most reported usage within the photocatalyst dataset. The cooccurrence between the usage and the catalysts within the photocatalyst dataset is presented in Figure .