2 research outputs found
Highly Water Dispersible Polymer Acid-Doped Polyanilines as Low-Cost, Nafion-Free Ionomers for Hydrogen Evolution Reaction
While
research efforts are devoted toward exploring low-cost electrocatalysts
for hydrogen evolution reaction (HER), little attention is paid to
another expensive component of the catalyst layerî—¸ionomers.
Both the electrocatalyst and a proportionately large amount of ionomer
are required for a large-scale production of hydrogen. Presently,
commercially available expensive Nafion is the state-of-the-art ionomer
for proton conduction in the electrocatalyst layer. Interpolymer composites
such as polymer acid-doped polyanilines (PANI) could be low-cost alternatives
to Nafion. Highly water-dispersible PANI polymers doped with polyÂ(2-acryl-amido-2-methyl-1-propanesulfonic
acid) (PAAMPSA)î—¸the polymer backbone of which is similar to
that of Nafionî—¸have been explored as cheaper alternatives to
Nafion in acid medium. PANI-PAAMPSA, polyÂ(<i>ortho</i>-toluidine)-PAAMPSA,
and polyÂ(<i>meta</i>-toluidine)-PAAMPSA have been used as
ionomers in MoS<sub>2</sub> and CoSe<sub>2</sub> electrocatalysts.
Electrocatalysts with PANI-PAAMPSA ionomers have achieved the highest
HER activities and the lowest Tafel slopes in comparison to that with
Nafion. Specifically, polyÂ(<i>meta</i>-toluidine)-PAAMPSA
has been found as a promising alternative to Nafion ionomer. Replacing
expensive Nafion in the electrocatalyst layer with PANI-PAAMPSA-based
ionomers would further reduce the cost of hydrogen in a large-scale
production
Single-Step Electrodeposited Molybdenum Incorporated Nickel Sulfide Thin Films from Low-Cost Precursors as Highly Efficient Hydrogen Evolution Electrocatalysts in Acid Medium
Large-scale
production of hydrogenî—¸the energy carrier of
the futureî—¸remains challenging on economy grounds. Low-cost
synthetic designs are necessary to produce electrocatalysts for hydrogen
evolution reaction (HER). Ternary nickel molybdenum sulfides Ni<sub>1–<i>x</i></sub>Mo<sub><i>x</i></sub>S
(<i>x</i> = 0, 0.04, 0.08, 0.16) have been electrochemically
grown on fluorine-doped tin oxide substrate as highly active and stable
HER electrocatalysts. The merits of this method are (1) the electrochemical
method is energy efficient at ambient conditions and can be easily
scaled up on large surface area substrates; (2) Ni, Mo, and S precursors
used for the deposition are readily available and relatively cheaper
compared to similar methods; and (3) the synthesis procedure is simple,
one step, and requires no further heat treatments. The deposited thin
films have been examined using regular physical characterization techniques,
and their HER activity has been evaluated through electrochemical
methods. Ni<sub>0.96</sub>Mo<sub>0.04</sub>S, especially, has exhibited
a promising HER activity with a lowest Tafel slope of 46 mV/dec. The
mechanistic aspects of HER on the thin films have been extensively
studied by voltammetric and impedance methods. Tafel analysis and
double-layer capacitance measurements have revealed that the high
activity of Ni<sub>0.96</sub>Mo<sub>0.04</sub>S can be attributed
to the larger electrochemical surface area and the faster discharge
of protons in the initial Volmer step. Moreover, stability tests performed
on various thin films have shown that Mo-doped thin films could retain
more than 80% of the initial activity whereas NiS has lost more than
50% of the same