posted on 2023-12-17, 22:20authored byYanming Li, Chenglong Ding, Yao Li, Jiahong Zeng, Caitao Kang, Honglei Chen, Lan Wang, Jingfu He, Changli Li
Si-based inhomogeneous metal–insulator–semiconductor
(MIS) junctions with a discontinuous metal nanostructure on the Si/insulator
layer are expected to be efficient photoelectrodes for solar energy
conversion. However, the formation of a metal nanostructure with an
optimized arrangement on semiconductors for efficient charge carrier
collection is still a big challenge. Herein, we report a method for
the in situ formation of an n-Si inhomogeneous MIS junction with well-dispersed
metal nanocontacts through a self-assembly process during photoelectrochemical
(PEC) methanol oxidation. The photovoltage shows a strong dependence
on the inhomogeneity of the n-Si MIS junction, which can be precisely
tuned by the applied electrode potential and operation time. The appropriate
inhomogeneity of the Schottky junction as well as the high barrier
regions induced by the metal oxide/(oxy)hydroxide layer synergistically
produces a large photovoltage of 500 mV for the n-Si inhomogeneous
MIS junction. Finally, the n-Si-based photoanode is coupled with a
CO2-to-formate reaction to realize the production of formate
at both electrodes, resulting in a high faradic efficiency (FE) of
86 and 93% for anode and cathode reactions at an operational current
of 30 mA/cm2, respectively. These findings provide important
insights into the design of highly efficient inhomogeneous MIS junctions
through an in situ self-assembly route for solar energy conversion
and storage.