The exploration of innovative substances is an essential undertaking in our efforts to shift the global energy framework from fossil fuels to renewable energy. Interestingly, it has been disclosed that this model can be inverted with the renewed exploration of traditional substances that facilitate extensive electricity retention and hydrogen creation — two essential aspects of the energy transformation.
A former editor of Nature magazine, Philip Ball, once remarked, “A breakthrough is an innovation teeming with potential, followed by strenuous effort.” Any researcher who has undergone a breakthrough — either intentionally or accidentally — recognizes the thrill of exploration and the joy of disseminating this newfound understanding with peers. Yet this is merely the initial phase in what’s often a many-decade journey towards technological applicability.
Naturally, the desire to commence and finish the cycle from exploration to application as quickly as possible is strong. The temptation to hasten this course, either through human creativity, fortune, or artificial intelligence, and to be the first to reach the end, by any means necessary, is compelling. However, the nuance lies in the fact that sometimes the materials required to tackle significant and urgent challenges don’t need to be unearthed; they are concealed treasures waiting to be found again. Two recent examples of traditional materials seem to have a high likelihood of influencing large-scale, economical grid-storage of electricity and the creation of golden hydrogen.
Illustrations of this notion of material re-exploration include metallic iron and a semiconductor known as silicon carbide, both thoroughly studied, plentiful, affordable, and harmless solids. Though being “ancient” substances, they have lately enabled two startup businesses to enlarge and assess the practical attributes of an iron-air battery and a silicon carbide solar water splitter, respectively.
The iron-air battery is in development by Form Energy, aiming for all-year grid electricity retention. The mechanism functions on an iron-iron oxide redox cycle; it’s entirely renewable, resilient, economical, and can consistently retain vast quantities of electricity for extended periods. The inaugural commercial item has an electricity retention capability of 100 hours at a total system cost that rivals traditional power plants. While its considerable weight and slow cycling rate render it unsuitable for electric cars, its extensive capacity renders it perfect for grid-size electricity retention.
The primary large-scale iron-air battery production plant of Form Energy is situated in West Virginia, USA. They are revitalizing a pre-existing steel factory, expected to employ over 750 individuals and produce 500 megawatts of batteries annually at full capacity. The yellow silicon carbide semiconductor, utilized for hydrogen creation from water and sunlight, is also now being fabricated on a grand scale by the Yellow SiC group. To perform well for water division into hydrogen, the substance must have extreme purity (below 1 ppm contaminants) and appear in the cubic polymorphic version of silicon carbide.
The electronic band characteristics of this kind of silicon carbide are essential for success. In particular, the electronic band gap is 2.36eV, closely aligned with the optimal band gap of 2.03eV that enhances the sunlight-facilitated water-splitting efficiency of a singular semiconductor material. Moreover, the electronic band configuration of this silicon carbide ideally aligns with the water’s oxidation and reduction potentials, a condition critically necessary for generating oxygen and hydrogen respectively, remarkably making it perfect for solar water division without external voltage bias.
This positions this “ancient” substance as the ideal choice for achieving independent (electricity-free) photochemical creation of hydrogen from water and sunlight. Although specific catalyst and apparatus details are scarce, the solar hydrogen photochemical creation module appears to be a basic, wireless layered structure composed of a thin film of yellow silicon carbide serving as the positive anode, where the water generates oxygen and protons. The silicon carbide interfaces with a negative metal cathode, where the electrons and protons formed at the silicon carbide combine to produce hydrogen. To finish the water division reaction, the protons must move between anode and cathode, a task seemingly aided by a proton-conducting membrane.
This straightforward apparatus is designated for rooftop solar hydrogen manufacturing plants. In operation, it enables stable, electricity-free production of the purest hydrogen form, termed golden hydrogen, directly from water and sunlight. Its estimated cost is $0.75-2.00 per kg of hydrogen, dependent on location and daily sunlight hours. These expenses seem to favor yellow silicon carbide as the preferred material for producing golden hydrogen, in contrast to green hydrogen from water electrolysis utilizing renewable electric energy, priced in 2022 at $4.48-6.71 per kg. The lesson of this narrative is not to supplant the exploration of new substances in the quest to craft sustainable energy technologies to alleviate current climate change issues. Instead, the emphasis is on continuous vigilance to the probability that numerous ancient materials are still to be found anew, potentially achieving or surpassing the same goals.