Highly Efficient Hybrid Ni/Nitrogenated Graphene Electrocatalysts for Hydrogen Evolution Reaction

Abstract

Two nickel/nitrogenated graphene hybrid electrodes ( Ni-NrGO NH3 and Ni-NrGO APTES ) were synthesized, and their catalytic activity with respect to the hydrogen evolution reaction (HER) in alkaline media was analyzed. Incorporation of nitrogen to the carbon structure in graphene oxide (GO) or reduced GO (rGO) flakes in aqueous solutions was carried out based on two different configurations. NrGO NH 3 particles were obtained by a hydrothermal method using ammonium hydroxide as the precursor, and NGO APTES particles were obtained by silanization (APTES functionalization) of GO sheets. Aqueous dispersions containing NrGO NH 3 and NGO APTES particles were added to the traditional nickel Watts plating bath in order to prepare the Ni-NrGO NH 3 and Ni-NrGO APTES catalysts, respectively. Nickel substrates were coated with the hybrid nickel electrodeposits and used as electrodes for hydrogen production. The Ni-NrGO catalysts show a higher activity than the conventional nickel electrodeposited electrodes, particularly the ones containing APTES molecules because they allow obtaining a hydrogen current density 130% higher than conventional Ni-plated electrodes with a Watts bath in the absence of additives. In addition, both catalysts show a low deactivation rate during the ageing treatment, which is a sign of a longer midlife for the catalyst. Cyclic voltammetry and electrochemical impedance spectroscopy measurements were used for examination of the catalytic efficiency of hybrid Ni-NrGO electrodes for HER in KOH solution. High values of exchange current densities, 8.53 × 10 –4 and 2.53 × 10 –5 mA cm –2 for HER in alkaline solutions on Ni-NrGO NH 3 and Ni-NrGO APTES electrodes, respectively, were obtained.

In situ fabricated nickel vanadate/N-doped reduced graphene oxide hybrid as an advanced electrocatalyst in alkaline hydrogen evolution reaction

“…Also, the presence of pyrrolic-N is responsible for the high electrical conductivity of NRGO, while pyridinic-N facilitates electrocatalytic activity. 28 Therefore, the optimised NRGO content in NV/NRGO2 is most likely to enhance the electrocatalytic HER performance of Ni 3…”

Dual-Nitrogen-Doped Carbon Decorated on Na3V2(PO4)3 to Stabilize the Intercalation of Three Sodium Ions

“…Interestingly, small traces of N are found in all electrodes and this could be due to the ammonium precursors used. , The high-resolution N 1s spectra in Figure c can be deconvoluted into three peaks at 398.3, 400.9, and 402.1 eV, corresponding to pyridinic-N, pyrrolic-N, and quaternary N, respectively, indicating that N has been doped into the carbon layer. , In Table , the majority of N in NVP@C/rGO-U existed in the form of pyridinic-N and pyrrolic-N (93.47 atom %), creating extrinsic defect sites in the carbon layer that can enhance both the ion and electron transportation through the layer. ,,, It is worth noting that NVP@C/rGO-U shows the highest pyrrolic-N, suggesting that the pyrolysis of urea NH 3 can engineer the type of defects in the carbon layer …”

“…36,38 In Table 1, the majority of N in NVP@C/rGO-U existed in the form of pyridinic-N and pyrrolic-N (93.47 atom %), creating extrinsic defect sites in the carbon layer that can enhance both the ion and electron transportation through the layer. 38,39,51,52 It is worth noting that NVP@C/rGO-U shows the highest pyrrolic-N, suggesting that the pyrolysis of urea NH 3 can engineer the type of defects in the carbon layer. 40 Field-emission scanning electron microscopy (FE-SEM) images of the composite NVP electrode in Figure 4a,b show that NVP@C has a clustered 3D porous structure.…”

Niobium-based semiconductor electrodes for hydrogen evolution reaction

“…We perform a series of Electrochemical Impedance Spectroscopy (EIS) measurements under dark -or under light-conditions, at four different electrode potentials (vs SCE): i) the pure Ni open circuit potential (OCP) reported as -0.36 V, 6 ii) pure Ni HER OP reported as -1.1 V, 6 iii) -1.2 V, and iv) -1.4 V. The potentials selected are the same as those commonly used in pure Ni electrodes, normally used in alkaline electrolysis. [54,55] Figure 4 shows the impedance spectra obtained for each three catalysts under dark -or under light-conditions at -1.2 V. The Ni-Nb2O5 impedance spectra show two semicircles, describing at least two processes occurring over the surface of the electrodes, as predicted by the impedance theory for HER. [56,57] One of the processes occurs at high frequencies (Figure 4A), corresponding to the capacitive processes occurring at the surface of the catalyst; and another one at low frequencies, associated with the HER -which clearly depends on the applied potential (cf.…”