posted on 2024-02-01, 17:43authored byNiharika Tanwar, Himani Narjinari, Harsh Sharma, Sunil Dhole, Raksh Vir Jasra, Akshai Kumar
Homogeneous electrocatalytic systems
based on readily available,
earth-abundant, inexpensive base metals Ni, Co, and Cr have been formulated
for the electro-oxidation of alcohols (methanol and ethanol) that
constitute a key half-cell component of direct alcohol fuel cells
(DAFCs). Notably, excellent results were obtained for both methanol
as well as ethanol electro-oxidation while operating with a half-cell
assembly based on all-non-noble working and counter electrode systems
consisting of glassy carbon and graphite rod, respectively. Using
NaOH as the supporting electrolyte, Ni/Co/Cr metal salts and their
bis(iminopyridine) complexes have been used as anodic electrocatalysts
for the alcohol half-cell reactions, and among them, catalytic systems
based on Co outperformed the corresponding systems based on Ni and
Cr. The system comprising CoCl2.·6H2O [10
mM] + NaOH [6 M] at room temperature emerged as the best electrocatalyst
for both methanol [5 M] electro-oxidation (ca. 522.5 ± 13.5 mA
cm–2 at 1.4 V) and ethanol [5 M] electro-oxidation
(ca. 209 ± 25 mA cm–2 at 1.34 V). It was observed
that regardless of the starting alcohol, the end product is carbon
dioxide, all of which gets trapped as sodium carbonate (up to 97%
yield), thereby mitigating any possible hazards of greenhouse gas
emission. Inferences obtained from FETEM, FESEM, and EDS analysis
of both the electrolyte solution and residues deposited on the electrode
surface provide evidence for the mostly homogeneous nature of the
reaction mixture with the molecular catalyst being the major contributor
toward the electrocatalytic activity apart from the minor role played
by trace heterogeneous particles. The current cell assembly operating
with non-noble working and counter electrodes utilizing a catalytic
system based on an earth-abundant, base metal salt/complex that not
only results in good half-cell current densities for high-energy power-source
DAFCs but also generates high-value sodium carbonate offers an exciting
avenue.