Electrocatalysts with engaging oxygen evolution reaction (OER) activity with lesser overpotentials are highly desired to have increased cell efficiency. In this work, cobalt selenide catalysts were prepared utilizing both wet-chemical route (CoSe and CoSe-DNA) and hydrothermal route (Co0.85Se-hyd). In wet-chemical route, cobalt selenide is prepared with DNA (CoSe-DNA) and without DNA (CoSe). The morphological results in the wet-chemical route had given a clear picture that, with the assistance of DNA, cobalt selenide had formed as nanochains with particle size below 5 nm, while it agglomerated in the absence of DNA. The morphology was nano networks in the hydrothermally assisted synthesis. These catalysts were analyzed for OER activity in 1 M KOH. The overpotentials required at a current density of 10 mA cm–2 were 352, 382, and 383 mV for Co0.85Se-hyd, CoSe, and CoSe-DNA catalysts, respectively. The Tafel slope value was lowest for Co0.85Se-hyd (65 mV/dec) compared to CoSe-DNA (71 mV/dec) and CoSe (80 mV/dec). The chronoamperometry test was studied for 24 h at a potential of 394 mV for Co0.85Se-hyd and was found to be stable with a smaller decrease in activity. From the OER study, it is clear that Co0.85Se was found to be superior to others. This kind of related study can be useful to design the catalyst with increased efficiency by varying the method of preparation.

Water electrolysis is a field growing rapidly to replace the limited fossil fuels for harvesting energy in future. In searching of non-noble and advanced electrocatalysts for the oxygen evolution reaction (OER), here we highlight a new and advanced catalyst, selenized Cu 3 Sn@Cu foam, with overwhelming activity for OER under both alkaline (1 M KOH) and near-neutral (1 M NaHCO 3 ) conditions. The catalysts were prepared by a double hydrothermal treatment where Cu 3 Sn is first formed which further underwent for second hydrothermal condition for selenization. For comparison, Cu 7 Se 4 @Cu foam was prepared by a hydrothermal treatment under the same protocol. The as-formed Cu 3 Sn@Cu foam, selenized Cu 3 Sn@Cu foam, and Cu 7 Se 4 @Cu foam were utilized as electrocatalysts and showed their potentiality in terms of activity and stability. In 1 M KOH, for attaining the benchmarking current density of 50 mA cm −2 , selenized Cu 3 Sn@Cu foam required a low overpotential of 384 mV and increased charge transfer kinetics with a lower Tafel slope value of 177 mV/dec comparing Cu 3 Sn@Cu foam, Cu 7 Se 4 @Cu foam, and pristine Cu foam. Furthermore, potentiostatic analysis (PSTAT) was carried out for 40 h for selenized Cu 3 Sn@Cu foam and with minimum degradation in activity assured the long-term application for hydrogen generation. Similarly, under neutral condition selenized Cu 3 Sn@Cu foam also delivered better activity trend at higher overpotentials in comparison with others. Therefore, the assistance of both Sn and Se in Cu foam ensured better activity and stability in comparison with only selenized Cu foam. With these possible outcomes, it can also be combined with other active, non-noble elements for enriched hydrogen generation in future.

Iron hydroxides are desirable alkaline battery electrodes for low cost and environmental beneficence. However, hydrogen evolution on charging and Fe3O4 formation on discharging cause low storage capacity and poor cycling life. We report that green rust (GR) (Fe2+ 4Fe3+ 2 (HO–)12SO4), formed via sulfate insertion, promotes Fe­(OH)2/FeOOH conversion and shows a discharge capacity of ∼211 mAh g–1 in half-cells and Coulombic efficiency of 93% after 300 cycles in full-cells. Theoretical calculations show that Fe­(OH)2/FeOOH conversion is facilitated by intercalated sulfate anions. Classical molecular dynamics simulations reveal that electrolyte alkalinity strongly impacts the energetics of sulfate solvation, and low alkalinity ensures fast transport of sulfate ions. Anion-insertion-assisted Fe­(OH)2/FeOOH conversion, also achieved with Cl– ion, paves a pathway toward efficient utilization of Fe-based electrodes for sustainable applications.

Rechargeable alkaline iron batteries that constitute environmentally benign electrolytes and earth-abundant industrial materials are desirable green solutions for large-scale energy storage. As one of the most abundant metal elements in the earth’s crust, iron (Fe) can satisfy nearly all criteria for low-cost and safe battery electrodes. However, challenges in achieving reversible Fe redox impede their extensive implementation in modern energy supply systems. This study revealed that Cl-anion insertion into Fe­(OH)2 layered double hydroxide (LDH) formed a green rust intermediate phase with the formula [Fe2 2+Fe1 3+(HO–)6]+[Cl]−, which assisted a high Fe­(OH)2/FeOOH conversion reaction (64.7%) and improved cycling stability. This new iron redox chemistry was validated by operando X-ray diffraction, electrochemical testing, X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS) analysis, scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy (STEM-EDS) mapping, and molecular dynamics (MD) simulations. Our study provides new insight into designing LDH materials for high-capacity alkaline iron batteries.