Efficient H₂ Evolution Coupled with Anodic Oxidation of Iodide over Defective Carbon-Supported Single-Atom Mo-N₄ Electrocatalyst

Abstract

We successfully prepared nitrogen-doped defective carbon spheres (Mo-N4/d-C) with a high loading of 0.996 wt % via a designed vapor-deposition process for IOR-based hydrogen generation. The synthesized Mo-N4/d-C catalyst provides a record current density of 10 mA cm–2 at 0.77 V. Further, the Mo-N4/d-C catalyst shows a Tafel slope of 25.58 mV dec–1, exceptional stability over time in acidic media, a higher hydrogen generation rate of 0.1063 mL gcat –1 min–1, a high Faradaic efficiency of 99.8%, and a reduction of the energy consumption up to ∼50% for hydrogen evolution by anodic oxidation reaction of iodide (IOR) compared with the conventional OER-based electrolysis. Computational calculations demonstrate that the Mo-N4/d-C structure plays a vital effect on the activity of iodide oxidation, which is competitive with the Pt catalyst.

Surface‐Passivated Vertically Oriented Sb2S3 Nanorods Photoanode Enabling Efficient Unbiased Solar Fuel Production

“…The IPCE of the two absorbers decreased within the range of below 400 nm because the iodine (i.e., a product of IOR) absorbed light with a wavelength less than 400 nm. [ 28 ] Importantly, the Sb 2 S 3 NR demonstrated an extraordinary light utilization ability over the entire wavelength range in comparison to the Sb 2 S 3 TF, verifying the improved charge carrier separation/injection capabilities of Sb 2 S 3 NR. Notably, compared with Sb 2 S 3 TF, Sb 2 S 3 NR revealed almost no loss in IPCE at wavelengths up to 675 nm.…”

Electrocatalysts for value-added electrolysis coupled with hydrogen evolution

“…In the case of iodide oxidation reactions, the process consists of two half-reactions (from eqn (1)–(3)):Anodic reaction: 2I − (aq) → I 2 + 2e − E ° = 0.54 VCathodic reaction: 2H + (aq) + 2e − → H 2(g) E 0 = 0.00 VOverall reaction: 2H + (aq) + 2I − (aq) → I 2 + H 2(g) Importantly, it is challenging to fabricate active and durable electrocatalysts for IOR-based electrolysis from the same low-cost precursor materials. After extensive research, our group discovered that electrocatalysts could be easily synthesized from metal oxides, single atoms, and metal-free carbon materials, such as ruthenium-tin surface alloy oxide (RuSn SAO), 13 self-supporting RuTiO oxide alloy, 52 defective carbon-supported single-atom Mo-N 4 /d-C electrocatalyst, 53 and graphite-based carbon fiber paper (CFP). 54 These electrocatalysts have abundant active sites and a delocalized electron system which play an important role in the adsorption, activation, and desorption of iodide ions at the catalytic sites, which are favorable for the production of valuable iodine and green hydrogen energy at a lower operating voltage.…”

“…The most pressing issue is to develop more value-added electrolysis processes and the corresponding electrocatalysts to 162 (c) Calaculated DFT of the metal-free based catalyst on IOR and the charge analysis between graphite and 3I À was performed in comparison with (d) that between Pt and 3I À . (e) The profiles of the potential energy surface (PES) for 3I À / I 2 + I À +2e À /I 3À + 2e À on the graphite surface.…”

“…54 (f) Schematic diagram of IOR in a H-type double cell with a proton exchange Nafion membrane. 162 help achieve the global goal of net-zero emissions by 2050. To bring the coupled system for value-added electrolysis (iodide oxidation reaction, poly-alcohol oxidation reaction, chitin oxidation reaction, urea oxidation reaction, and hydrazine oxidation reaction) with HER to a practical level, we must address the related technological, economic, and environmental issues, On top of that, the most important performance metrics, such as total current density, faradaic efficiency of different products, stability, and overpotential of value-added chemicals, should be reported for comparison of published works and predict the levelized cost of chemicals at various technology levels.…”

“…10 Calculated DFT of the metal and metal free electrocatalysts for IOR. (a) The free energy diagram of Mo-N 4 /d-C. (b) Comparisons of iodide adsorption and iodine desorption on different catalyst surfaces 162. (c) Calaculated DFT of the metal-free based catalyst on IOR and the charge analysis between graphite and 3I À was performed in comparison with (d) that between Pt and 3I À .…”