Harnessing Native Iron Ore as an Efficient Electrocatalyst for Overall Water Splitting

Abstract

Electrochemical water splitting is a widely accepted approach to generate hydrogen at a scale that is suitable for storing renewable energy. Therefore, the choice of catalyst for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are critical in terms of cost when scaling up this technology. Thus, earth abundant transition metals oxides and sulfides have received significant attention as catalysts for the OER and HER, respectively. However, very few examples of actual Earth abundant materials mined from the Earth's crust have been used as electrocatalysts for these reactions. Here, we demonstrate that a raw iron ore is active for both the HER and OER under alkaline conditions, which is due to the natural abundance of the key elements of iron, nickel, and sulfur. The catalyst is stable for both reactions and can operate at 100 mA cm À 2 , which is comparable to many chemically synthesised nanomaterials based on these elements. This approach may be attractive for adding value to iron ore while minimising the cost of catalyst production.[a] Dr.

Activating Iron Based Materials for Overall Electrochemical Water Splitting via the Incorporation of Noble Metals

“…The observed lattice spacings for the sample after the OER (Figure 7b) showed similar values with the addition of lattice spacings of 0.31 and 0.14 nm, which correspond to Fe 3 O 4 (511) and Au (220) planes, respectively [29–30] . It was noted that there was an increase in iron oxide crystallinity across the sample after the OER which has been observed previously for Fe and Co oxide materials [6r,10b,31] …”

“…In addition, mixed metal oxides using Fe has emerged as an important combination for improving activity. The fabrication of FeNi, FeCo and FeNiCo oxides/hydroxides have shown excellent electrocatalytic activity where the presence of Fe is the key consideration [6d,r,7b,8] . Indeed, Bell et al .…”

Tailoring the Electrocatalytic Activity of Pentlandite FexNi9‐XS8 Nanoparticles via Variation of the Fe : Ni Ratio for Enhanced Water Oxidation

“…Several reports have demonstrated that the surface of metal sulphides is indeed oxidized to metal oxide/hydroxide, which were deduced to be the active species for OER, prior to OER along with sulphur depletion from the surface. [24,37,40] Consequently, the variation of the electrocatalytic activity with altered Fe : Ni ratio can be explained by the increased Ni 3 + active sites with the increase of the Ni content, considering Ni 3 + surface ions as the active sites in this pentlandite structure. Upon inclusion of more Fe into the structure, the amount of Ni 3 + on the surface is supressed and thus the activity is reduced.…”

“…The 3d-iron group catalysts are known to undertake oxidation to higher oxidation states forming metal oxyhydroxide in alkaline media which is approved as the active species for OER. [24,25] Consequently, transition metal-rich pentlandites with variable oxidation states are potentially active OER catalysts. Though, only a few reports discussed the use of pentlandites for OER and even those investigated pentlandites have often required conductive supports or involved long synthetic procedures as in the case of hollow Co 9 S 8 cubes.…”

“…[19,28] In another study, a raw iron ore containing pentlandite phase (obtained near Whitehorse, Canada) electrode was illustrated to be HER and OER active due to the formation of NiOOH active species on its surface upon oxidation. [24] Nevertheless, developing new catalysts often still depends on complex synthetic routes and often nanostructuring. Therefore, exploring simple strategies to systematically design efficient oxygen evolution electrocatalysts via the careful variation of their metal stoichiometry is essential.…”