A well-organized
worldwide effort in providing remedies to sustainable
clean energy generation and storage has focused on the strategic design
and development of stable and efficient earth-abundant metal (Fe,
Co, Ni, Pb, etc.)-based electrocatalysts for the oxygen evolution
reaction (OER). Unfortunately, examples of Pb-based catalysts for
such a process are rare. In this work, based on the dual-linker strategy,
we have designed and synthesized two new two-dimensional (2D) coordination
polymers of Pb with the hcb topology, [Pb2(tpbn)(adc)2]·4H2O·0.5CH3OH}
n
(CP1) and {[Pb2(tpbn)(fum)2]·7H2O}
n
(CP2), in excellent yields by the room-temperature
self-assembly of Pb(OAc)2, tpbn, and H2adc or
H2fum (where tpbn = N,N′,N‴,N‴′-tetrakis-(2-pyridylmethyl)-1,4-diaminobutane,
H2adc = acetylene dicarboxylic acid, and H2fum
= fumaric acid). In addition to determining their X-ray single crystal
structures, the phase purity and thermal stability were established
by powder X-ray diffraction and thermogravimetric analysis, respectively.
Furthermore, these were also characterized by the microscopic techniques
(SEM/EDX and TEM/HRTEM). For their conductive and highly stable nature
in alkaline medium, both CP1 and CP2 were
tested for their suitability in the OER process. Interestingly, with
a subtle change from adc in CP1 to fumarate in CP2 as the dicarboxylate linker, the latter performed much
better than the former and displayed an excellent electrochemical
stability in basic medium. Remarkably, CP2 has one of
the lowest Tafel values (35 mV dec–1) and a low
overpotential value (140 mV vs RHE) in 0.5 M KOH compared to those
reported for any materials. Such a comparative study with CP1 and CP2, which are the simplest CPs and made with green-chemistry
protocols for an easy making in large quantities, provides an outlook
to developing the next-generation Pb-based electrocatalysts.
