Unveiling the Selectivity of CO₂ Reduction on Cu₂ZnSnS₄: The Effect of Exposed Termination

Abstract

With the advantage of excellent light absorption ability and earth-abundant elements, Cu2ZnSnS4 (CZTS) is widely applied in the photoelectrochemical (PEC) reduction of CO2. However, the microscopic mechanism of the CO2 conversion on CZTS is still unclear. Here, we have theoretically investigated the electronic properties of the CZTS to reveal the special bonding properties of CO2 under both exposed metal and sulfur terminations of the CZTS and the formation mechanisms of producing CO, HCOOH, and CH4 from a microscopic perspective. Our study shows that when the metal is exposed to the surface, CO2 will convert to HCOOH with a high selectivity with the limiting potential of 0.23 V (vs RHE). However, on the sulfur termination, the onset potentials of producing HCOOH, CO, and CH4 are all lower than 0.4 V, indicating the mix formations. These findings provide theoretical insight into the PEC experiments of CO2 reduction on CZTS.

Theory-Guided S-Defects Boost Selective Conversion of CO2 to HCOOH over In4SnS8 Nanoflowers

“…Subsequently, the wide band gaps (between 2.8 and 4.2 eV, Table S1) of the oxide layer not only severely restrict its conductivity and catalytic performance but also challenge its stability due to the loss of surface metallic active sites. − In comparison, various low-melting-point metal sulfides exhibit better conductivity on account of their narrower band gap (Table S1), making them easier to serve as electrocatalysts. Moreover, recent studies have shown that the synergistic effect of metals with sulfur has better performance in the CO 2 RR to HCOOH, − rivaling all the unoxidized bare low-melting-point metal catalysts. Sulfides generally exhibit abundant sulfur vacancy defects that could serve as active sites, featuring the defect-tuned localized electronic structure to boost CO 2 RR performance.…”

Materials design of edge-modified polymeric carbon nitride nanoribbons for the photocatalytic CO2 reduction reaction

“…The complex reaction paths and product selectivity of the CO 2 RR have been widely explored. 59,60 For example, *COOH will generate three different intermediates (*CO, *HCOOH, and *COHOH) according to the different bonding methods of hydrogen, which determines the production of CO, HCOOH, and others. The *CH 3 OH and *CH 2 intermediates are generated by different hydrogenation of *CH 2 OH (C–H and O–H), which determine the formation of CH 3 OH or CH 4 .…”

“…The complex reaction paths and product selectivity of the CO 2 RR have been widely explored. 59,60 to CO 2 is beneficial to confine it within the vacancy (Fig. S3, ESI †), while the combination of the heptazine ring and COOH expands the delocalized range and further stabilizes the intermediate *COOH.…”

Zinc-Based Materials for Photoelectrochemical Reduction of Carbon Dioxide

“…While when the exposed atoms are S atoms, the reduction product is a mixture of formic acid, CO, and methane at potentials less than −0.4 V (vs RHE). 87 Furthermore, Zhang et al using DFT calculations predicted that a (220) facet-suppressed kesterite CZTS could be an efficient photoelectro-integrated photocathode for formic acid production. This is supported by the fact that the (220) facet of CZTS is particularly favorable for competitive HER.…”

“…When the exposed atoms are Cu atoms, formic acid is the main product at potentials higher than −0.23 V (vs RHE). While when the exposed atoms are S atoms, the reduction product is a mixture of formic acid, CO, and methane at potentials less than −0.4 V (vs RHE) . Furthermore, Zhang et al using DFT calculations predicted that a (220) facet-suppressed kesterite CZTS could be an efficient photoelectro-integrated photocathode for formic acid production.…”