Study Of Oxygen Evolution Reaction Research Articles

Influence of Ni2+ on OER kinetics and photoluminescence properties of ZnSnO3 nanoparticles

Ni2+ doped ZnSnO3 nanoparticles (NPs) were synthesized using Aloe vera mediated solution combustion method, followed by an investigation into their luminescence and oxygen evolution reaction properties. The Bragg reflections of ZnSnO3: Ni(1–9 mol%) NPs revealed a cubic structure, with the addition of the dopant inducing lattice strain and resulting in peak shifting towards higher angles. No impurity-related peaks were observed. The estimated crystallite size and optical band gap decrease (3.1–2.94 eV) with an increase in dopant concentration. The surface morphology consists of irregular-sized and shaped NPs with hallows. The EDAX spectra show the purity of the sample. Photoluminescence emission spectra were recorded at a 230 nm excitation wavelength, where intense blue emission observed at 482 nm was attributed to a direct transition between the conduction band edge and the valence band edge, corresponding to the direct recombination of free excitons. Another satellite peak observed at 525 nm can be attributed to oxygen deficiency. Moreover, the nanoparticles exhibited outstanding performance in oxygen evolution reaction studies, showing low over potentials between 300 and 318 mV, a minimal Tafel slope of range 63–72 mV dec−1, and stable electrochemical behavior over 12 h at a current density of 23 mA/cm2. These results highlight their effectiveness as electrocatalysts.

Computational study of oxygen evolution reaction on flat and stepped surfaces of strontium titanate

Oxygen evolution reaction (OER) is reconciled with the bottleneck in hydrogen production via photo- or electrocatalytic water splitting. One of the remedies to overcome this shortcoming is to develop catalytically efficient anode materials. Strontium titanate (STO) is a potential candidate for the OER by referring to recent experimental reports on enhanced photocatalytic activity of faceted nanoparticles. In this paper, we perform electronic structure calculations in the density functional theory approximation to study the OER on flat and stepped surfaces, such as encountered in nano-sized STO. We demonstrate that stepped surfaces reveal higher OER activity than flat surfaces, which is consistent with experimental data. We also observe partial breaking of OER scaling relation on stepped surfaces, albeit this does not necessarily cause higher catalytic activity. Finally, we propose recommendations for thorough implementation of zero-point energy calculations as the calculation method may impact the free-energy landscape of the OER.

First-Principles Study of Oxygen Evolution Reaction on Ir with Different Coordination Numbers Anchoring at Specific Sites of Co3O4 (111) Surface

First-Principles Study of Oxygen Evolution Reaction on Ir with Different Coordination Numbers Anchoring at Specific Sites of Co3O4 (111) Surface

Design and fabrication of cobaltx nickel(1-x) telluride microfibers on nickel foam for battery-type supercapacitor and oxygen evolution reaction study

Tellurium (Te) is a metal with the ability to function as a self-sacrificing template and exhibits strong chemical reactivity with counter metals. By the simple inward diffusion of metal ions on its surface, it can form long one-dimensional architect. Utilizing this, a one-dimensional cobaltx nickel(1-x) telluride (CoxNi(1-x)Te) microfibers (MFs) on nickel foam substrate has been constructed for a bifunctional electrode application. The theoretical and experimental investigations on the CoxNi(1-x)Te validates the Co0.75Ni0.25Te superiority over other ratios. The synergistically caused effects at 3:1 Co/Ni ratio reactivity with Te enhance the microstructure bifunctional electrode property with excellent stability during long cycle operation. The density functional theory calculations of Co0.75 Ni0.25Te revealed a better quantum capacitance due to the increased density of states near Fermi levels and achieved the enhanced oxygen evolution reaction activity because of increasing OH coverage. The assembled device Co0.75Ni0.25Te MF//activated carbon achieves outstanding energy storage performance with a maximum energy density of 50.8 Wh/Kg (58.4 μWh/cm2) at a power density of 672.7 W/Kg (773.5 μW/cm2) and sustains the performance up to 10,000 cycles, with a capacity retention of 90.1%. As an electrocatalyst, Co0.75Ni0.25Te MF/nickel foam requires a low overpotential (η) of 289 mV to reach a current density (j) of 10 mA/cm2 in 0.1 M KOH for oxygen evolution reaction.

Oxygen evolution catalysts under proton exchange membrane conditions in a conventional three electrode cell vs. electrolyser device: a comparison study and a 3D-printed electrolyser for academic labs

In academic labs, most oxygen evolution reaction studies are carried out in conventional three-electrode cell set-ups; however, this configuration may not accurately represent conditions experienced under practical electrolyser conditions.

Ab initio study of oxygen evolution reaction and hydrogen evolution reaction via water splitting on pure and nitrogen-doped graphene surface

Water electrolysis is widely considered to be a realistic technology for large, highly purified hydrogen production. In recent years, electrocatalytic water splitting achieved by graphene hybrids has received wide recognition; additionally, nitrogen (N)-doped carbon materials have shown promising catalytic activity for oxygen-reduction reactions (ORR) as metal-free alternatives to platinum. In an effort to elucidate the underlying molecular mechanism that drives such high catalytic activity, density functional theory (DFT) calculations were applied to oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) on pristine and N-doped graphene surfaces. A wide portfolio of investigations was carried out on pristine, 1.7% N-doped, and 3.3% N-doped graphene systems including water adsorption energy calculations, charge density differences calculations, the density of states (DOS) and band structure comparisons. The defect formation energy of 3.3% N-doped graphene for different configurations has been carried out to find the most stable configuration. Lastly, the nudged elastic band (NEB) theory was utilized to estimate the reaction coordinate and minimum energy path (MEP) at each stage of the reaction. By modulating N-doping concentration on the graphene layer, the MEP of the reaction coordinate was calculated. It was found that the barrier potential of energetic elementary steps decreases with increasing N-doping concentration. Finally, our results reveal that the primary reasons that drive an efficient water-splitting reaction include the nitrogen species’ intrinsic electronegativity together with a shift of the Fermi level towards the conduction band, thus making the system more conductive.

Study of oxygen evolution reaction on thermally prepared xPtOy-(100-x)IrO2 electrodes

The mixed coupled xPtOy-(100-x)IrO2 electrodes (x = 0, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100) were thermally prepared at 450 °C on titanium supports. The prepared electrodes were firstly physically characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Afterwards, electrochemical characteri­zations were performed by voltammetric (cyclic and linear) methods in different electrolyte media (KOH and HClO4). It is shown that the prepared electrodes are composed by both PtOy (platinum and platinum oxide) and IrO2 (iridium dioxide). For xPtOy-(100-x)IrO2 electrodes having higher content of IrO2, more surface cracks and pores are formed, defining a higher surface area with more active sites. Higher surface area due to presence of both PtOy and IrO2, is for xPtOy-(100-x)IrO2 electrodes in 1 M KOH solution confirmed by cyclic voltammetry at potentials of the oxide layer region. For all prepared electrodes, voltammetric charges were found higher than for PtOy, while the highest voltammetric charge is observed for the mixed 40PtOy-60IrO2 (x = 40) electrode. The Tafel slopes for oxygen evolution reaction (OER) in either basic (0.1 M KOH) or acid (0.1 M HClO4) media were determined from measured linear voltammograms corrected for the ohmic drop. The values of Tafel slopes for OER at PtOy, 90PtOy-10IrO2 and IrO2 in basic medium are 122, 55 and 40 mV dec-1, respectively. For other mixed electrodes, Tafel slopes of 40 mV dec-1 were obtained. Although proceeding by different OER mechanism, similar values of Tafel slopes were obtained in acid medium, i.e., Tafel slopes of 120, 60 and 39 mV dec-1 were obtained for PtOy, 90PtOy-10IrO2 and IrO2, and 40 mV dec-1 for other mixed electrodes. The analysis of Tafel slope values showed that OER is more rapid on coupled mixed electrodes than on pure PtOy. For mixed xPtOy-(100-x)IrO2 electrodes, OER is more rapid when the molar percent of PtOy meets the following condition: 0 ˂ x ≤ 80. This study also showed that the mixed coupled electrodes are more electro­cata­lytically active for OER than either PtOy or IrO2 in these two media.

First-principles study of oxygen evolution reaction on Ni3Fe-layered double hydroxides surface with different oxygen coverage

The oxygen evolution reaction performance was studied in the different oxygen coverage on the 110 surface of Ni3Fe-layered double hydroxides by the first-principles. The OER activities on three O covered surfaces were compared with clean surface. The three different O covered surfaces included (i)1/4 monolayer O covered, (ii) 1/2 monolayer O covered, (iii) 3/4 monolayer O covered surface. The computed overpotential (η) on the four cases followed the order: 1/4 monolayer < clean < 1/2 monolayer < 3/4 monolayer. And the overpotential of the active site has the following order 1/4 monolayer Fe < 1/4 monolayer Ni. By calculating the partial density of states and Bader charge on the O covered surface, it was found that 1/4 monolayer O covered surface combined with the formation OH easily. Based on the above analysis, the 1/4 monolayer O covered Ni3Fe-layered double hydroxides surface exhibited better OER catalytic performance than that of the clean surface in the OER cycle.