posted on 2022-12-12, 20:04authored byLingzhe Fang, Xingyi Lyu, Jason J. Xu, Yuzi Liu, Xiaobing Hu, Benjamin J. Reinhart, Tao Li
Tin-based electrocatalysts exhibit
a remarkable ability
to catalyze
CO2 to formate selectively. Understanding the size–property
relationships and exploring the evolution of the active size still
lack complete understanding. Herein, we prepared SnO2 nanoparticles
(NPs) with a controllable size supported on commercial carbon spheres
(SnO2/C-n, n = 1, 2,
and 3) by a simple low-temperature annealing method. The transmission
electron microscopy/scanning transmission electron microscopy images
and fitting results of the small-angle X-ray scattering profile confirm
the increased size of SnO2 NPs due to the increase of SnO2 loading. The catalytic performance of SnO2 has
proved the size-dependent effect during the CO2 reduction
reaction process. The as-prepared SnO2/C-1 displayed the
maximum Faradic efficiency of formate (FEHCOO–)
of 82.7% at −1.0 V versus reversible hydrogen electrode (RHE).
In contrast, SnO2/C-2 and SnO2/C-3 with larger
particle sizes achieved lower maximum FEHCOO– and
larger overpotential. Moreover, we employed operando X-ray absorption
spectroscopy to study the evolution of the oxidation state and local
coordination environment of SnO2 under working conditions.
In addition to the observed shifts of the rising edge of Sn K-edge
X-ray absorption near-edge structure spectra to a lower energy side
as the applied voltage decreases, the decreased coordination number
of Sn in the Sn–O scattering path and the presence of Sn metal
contribution in the extended X-ray absorption fine structure spectra
verify the reduction of SnO2 to SnOx and metallic Sn.