The diversity in materials used in Hydrogen Fuel Cell Devices in GHE research has slowly declined (See Figure ), with 2013 being the year with the highest number of distinct subtances being researched. The major interest throughout the decade has been in Oxides due to the growing interest in materials for SOFCs. The constant appearance of Organic/Inorganic Small molecules is mostly due to electrolyte components like water, acids as alternative electrolytes (ex: phosphoric acid and sulfuric acid fuel cells), alternative oxidants like H2O2, 240 and association with chemical hydrogen storage like ammonia and methanol. Polymer interest is due to research for membranes for the PEMFC and AEMFC electrolytes. There has been some continued interest in substances under the Alloys and Elements designation due to catalyst research. As before mentioned, the never ending pursuit of more affordable yet effective catalysts is also reflected in the interest of nanoparticles (Table ). Just like in the case of Green Hydrogen Production and Hydrogen Storage, nanoparticles and nanomaterials are playing a big role in hydrogen fuel cells. The application of these materials is diverse, but the literature shows that the main interests are for the increase of surface area, porosity or just general improvements in morphology of Fuel Cell catalysts, especially for ORR. This is further explored and demonstrated in the features of the most popular substances in hydrogen fuel cell research and their exemplary publications shown in Table . Many of the substances in Table are comprised of the highlighted elements on Figure . Some of the highlighted elements are part of basic components of fuel cells, for example: hydrogen as fuel; oxygen for ORR or oxides in electrodes; Pt, Ni,N, Fe and C for catalysts, etc. Still table did not show all substances associated with solid oxide fuel cell electrolytes and electrodes, especially the important perovskite like ceramics. These are reflected in Figure by the high occurrence of Co, La and Sr.