Bismuth porous nanosheets (Bi PNSs) were synthesized
via a three-step
process in the absence of any surfactants and templates. As a catalyst
for electrochemical CO2 electroreduction, Bi PNSs show
high selectivity to formic acid with the maximum Faraday efficiency
of 95.31% and maintain more than 80% Faraday efficiency over a wide
voltage range of 1100 mV. The excellent performance of Bi PNSs was
found to originate from the abundant kink sites on the pore walls,
which have appropriate affinity to intermediates and reduce the energy
barriers for CO2 electroreduction. Our work demonstrates
that a clean synthetic route is advantageous to the growth of a unique
nanostructure that possesses high catalytic activity.
Electron transfer at the metal−solution interface is crucial to an electrocatalytic reaction, which is generally recognized as a rate-determining step. So far, there is still lack of a universal experimental electrochemical quantity strongly correlated with the interfacial electron transfer rate for different kinds of catalysts, limiting the design of superior electrocatalysts for a given electrocatalytic reaction. Here, we propose that the potential of zero charge (PZC) is theoretically and experimentally correlated with the interfacial electron transfer rate and thus profoundly affects the activity and selectivity of CO 2 electroreduction to formate for Bi, In, Sn, and Pb. PZC takes into account the contributions from both the work function of catalysts and the change in the electron overlapping distribution at the catalyst surface induced by the solvent dipoles. The higher the PZC, the faster the interfacial electron transfer rate of CO 2•− formation in the process of CO 2 electrochemical reduction to formate. Thus, the promotion by accelerating the interfacial electron transfer leads to higher electrocatalytic activity and selectivity for yielding formate. This study demonstrates the relationships between PZC and activity and selectivity, and further lays a theoretical foundation for in-depth insight into the electrocatalytic mechanism of different kinds of metals on highly yielding the same product.
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