Significance of interface barrier at electrode of hematite hydroelectric cell for generating ecopower by water splitting

Abstract

Summary Recent increase in energy demand and associated environmental degradation concern has triggered more research towards alternative green energy sources. Eco‐friendly energy in facile way has been generated from abundantly available iron oxides using only few microliters of water without any external energy source. Hydroelectric cell (HEC) compatible to environment benign, low cost oxygen‐deficient mesoporous hematite nanoparticles has been used for splitting water molecules spontaneously to generate green electricity. Hematite nanoparticles have been synthesized by coprecipitation method. Chemidissociated hydroxyl group presence on hematite surface has been confirmed by infrared spectroscopy (IR) and X‐ray photoelectron spectroscopy (XPS). Surface oxygen vacancies in nanostructured hematite have been identified by transmission electron microscopy (TEM), XPS, and photoluminescence (PL) measurement. Hematite‐based HEC delivers 30 mA current with 0.92 V emf using approximately 500 μL water. Maximum off‐load output power 27.6 mW delivered by 4.84 cm2 area hematite‐based HEC is 3.52 times higher than reported 7.84 mW power generated by Li‐magnesium ferrite HEC. Electrochemistry of HEC in different irreversible polarization loss regions has been estimated by applying empirical modeling on V‐I polarization curve revealing the reaction and charge transport mechanism of cell. Tafel slope 22.7 mV has been calculated by modeling of activation polarization overvoltage region of 0.11 V. Low activation polarization indicated easy charge/ion diffusion and faster reaction kinetics of Ag/Zn electrode owing to lesser energy barrier at interface. Dissociated H3O+ ions diffuse through surface via proton hopping, while OH− ions migrate through interconnected defective crystallite boundaries resulting into high output cell current.

Electricity generation by splitting of water from hydroelectric cell: An alternative to solar cell and fuel cell

“…In Figure 9G,H, for MgO and SiO 2 high‐frequency semicircle loop is suppressing the Nyquist plots due to high values of bulk resistance R b . High resistance of MgO and SiO 2 impedes the motion of ions confirmed by EIS fitting value 43 . It can be inferred from the curve that both inherent as well as external properties are responsible for electric power generation.…”

“…70 When the cells were soaked with 16 MΩ resistive deionized water, a remarkable drop in impedance occurs to 100 Ω depicted in Figure 9C,H. 43 In wet condition, the cells at lower frequency region shows a tail which is referred as diffusion of H 3 O + ion at the Ag electrode ( Figure 9) and at high frequency, a capacitive tail appears owing to the formation of Zn(OH) 2 at Zn anode for magnetite and Lithium substituted magnesium ferrite HEC. 34,71,72 In Figure 9G, H, for MgO and SiO 2 high-frequency semicircle loop is suppressing the Nyquist plots due to high values of bulk resistance R b .…”

“…Till now 12 research papers have been published in SCI peer reviewed international journals by Kotnala et al group and nine from other groups in last 3 years. [37][38][39][40][41][42][43][44][45][46] With further study of base material, the initial key material magnesium ferrite with nominal lithium substitution has been strategically processed and engineered to make it Nano porous and oxygen deficient for water splitting at room temperature. Magnesium ferrite is a soft magnetic material (general formula AB 2 O 4 ) and it is highly resistive among all ferrites due to oxygen vacancies.…”

“…It results into a continuous flow of electric current and voltage developed in the cell. Till now 12 research papers have been published in SCI peer reviewed international journals by Kotnala et al group and nine from other groups in last 3 years 37‐46 . With further study of base material, the initial key material magnesium ferrite with nominal lithium substitution has been strategically processed and engineered to make it Nano porous and oxygen deficient for water splitting at room temperature.…”

Influence of Microwave Irradiation and Combustion Fuels on the Rate Capability and Cycle Performance of Li1.2Mn0.52Ni0.13Co0.13Al0.02O2 Layered Material

“…The main peak at 530.1 eV corresponds to the lattice oxygen, whereas the higher binding energy peaks at 531.8 and 533.9 eV correspond to OH À and H 2 O species, respectively [46]. The peak at 531.8 eV also corresponds to the oxygen vacancies in metal oxides [47][48][49]. The fitted data for O 1s peak is shown in Table 2, the LMNCA EG-mic and LMNCA urea-mic show low lattice oxygen content and high content of the surface hydroxyl oxygen compared to the non-microwaved samples.…”