Tailoring CoNi alloy embedded carbon nano-fibers by thiourea for enhanced hydrogen evolution reaction

A Self-Supporting Electrode Material (NiS/NF) as a Stable and Efficient Electrocatalyst for Oxygen Evolution: In Situ Surface Activation of Nickel Sulfide to Nickel Oxide/(Oxy)hydroxide

“…: 04-0850), and (101), (110), (003), (202), and (113) planes of Ni 3 S 2 are represented by the notable diffraction peaks at 21.901°, 31.200°, 37.911°, 44.581°, and 49.786°, respectively (JCPDS card no. : 44-1418). ,, The HR-TEM and XRD results are consistent with each other, and the electron interaction between nickel and Ni 3 S 2 was enhanced by excellent lattice matching. The oxidation states of the elements on the surface of NiS/NF can be analyzed by X-ray photoelectron spectroscopy (XPS) and characterize the elemental valence distribution of nickel and sulfur (Figure h).…”

“…The NiS species could be responsible for the redox peak at around 1.2 to 1.45 V (oxidation @ 1.38 V; reduction @ 1.28 V) (Figure S5). ,, In 1.0 M KOH, IrO 2 /NF and bare NF were used as the control to assess OER catalytic efficiency. As seen in Figure a, bare NF has very lower OER activity, whereas the as-synthesized NiS/NF reveals excellent OER activity with 1.52 V versus RHE potential and enhanced current density compared to IrO 2 /NF (1.60 V) and bare NF (1.64 V).…”

“…The Nyquist plot reveals that NiS/NF (5.2 Ω) shows smaller resistivity than IrO 2 / NF (6.1 Ω) and bare NF (8.9 Ω), which confirms the rapid charge-transfer ability of NiS/NF during water oxidation. The equivalent circuit [ R S , solution resistance ( R 1 ); R ct , charge transfer resistance ( R 2 ); CPE/ C dl , constant phase element ( Q 2 )] is attained from Z-fit (Figure S7) of the evaluated Nyquist plot. , The parameter Q 2 may be used as an alternative to capacitance since the electrode in the electrochemical process has a considerable degree of roughness and inhomogeneity. Figure b reveals the NiS/NF long-term stability of the three-electrode system in 1.0 M KOH at a fixed overpotential of 290 mV.…”

“…RuO 2 and IrO 2 are the most common OER electrocatalysts, but they are scarce and inexpensive . Researchers developed earth-abundant group IV transition metal catalysts such as Fe-based, Co-based, − Ni-based, Mn-based, , Cu-based, bimetal-based, − and trimetal-based catalysts, selenides (NiSe), and sulfides (Ni−S and Co−S) to replace the benchmark catalysts. Because of their poor conductivity and minor specific surface area, new strategies have been proposed to enhance the activity − : (i) a combination of non-noble metal catalysts with conductive carbon-based materials and (ii) a potential strategy have been made to overcome those difficulties by directly placing the catalysts on metal substrates. − By employing carbon-based powdery catalysts, the postcoating technique shows high cost, low conductivity, low overpotential, and low stability @ 10 mA/cm 2 in 1.0 M KOH. ,, Also, the design criteria for large current density (OER) were yet unclear.…”

Structural and compositional analysis of MOF-derived carbon nanomaterials for the oxygen reduction reaction

“…This pleating disrupts the original charge balance and contributes to catalyst performance. [88][89][90] While the charge transfer generated by sole S doping is negligible due to the similar electronegativity of S and C atoms, co-doping with N generates asymmetric spins and charge densities, contributing to oxygen adsorption and charge transfer. 88,89 The content of element S in the catalyst can be regulated by controlling the thiourea content in the precursor.…”