A Bismuth Species-Decorated ZnO/p-Si Photocathode for High Selectivity of Formate in CO₂ Photoelectrochemical Reduction

Abstract

Photoelectrochemical (PEC) reduction of CO2 to high value-added chemicals or fuel is an effective way to remit insufficient energy supply and global warming. Herein, Bi species-modified p-n heterojunction ZnO/p-Si was synthesized by a hydrothermal method and a subsequent electrodeposition process. For the PEC CO2 reduction reaction (CO2RR), the obtained photocathode Bi-Bi2O3/ZnO/p-Si not only improves the light absorption capacity because of p-Si and plasma metal Bi, but also increases the selectivity of CO2 reduction products because of the existence of Bi species. In particular, compared with the electrochemical CO2RR, the faraday efficiency of formate shows a 1.8 fold increase for the optimal sample Bi-Bi2O3/ZnO/p-Si reaching 84.3% in the PEC CO2RR at −0.95 V vs RHE. More importantly, the current density and product selectivity have no decay within 8 h, implying its high stability. In addition,, a high applied bias photon-to-current efficiency of 1.14% and an energy efficiency value of 56.21% were achieved for the Bi-Bi2O3/ZnO/p-Si photocathode at −0.95 V vs RHE, confirming its high PEC activity. A possible electron transfer mechanism for the Bi-Bi2O3/ZnO/p-Si photocathode is also proposed.

Modulating the Cu2O Photoelectrode/Electrolyte Interface with Bilayer Surfactant Simulating Cell Membranes for Boosting Photoelectrochemical CO2 Reduction

“…The comparison shows that the yield of the Cu 2 O/Sn/DHAB photoelectrode is better than those of most of the currently reported photoelectrodes whose product is HCOOH (Figure g and Table S1). − …”

Zinc-Based Materials for Photoelectrochemical Reduction of Carbon Dioxide

“…Similar to anatase TiO 2 , ZnO also has a wide energy bandgap (3.3 eV) and a suitable conduction band position (−0.5 eV), which allows it to absorb UV light to active PEC reactions . Although ZnO possesses some advantages such as nontoxicity, low cost, easy preparation, high chemical stability, low dielectric constant, and low optical coupling rate, it absorbs only UV light and suffers serious photocorrosion under light illumination .…”

“…Therefore, improving the light absorption efficiency is the first challenge to develop ZnO-based photocatalysts. The common strategies include doping metal and/or nonmetal elements and constructing heterostructures. − Doping with metal ions creates impurity levels below the conduction band or above the valence band acting as donor or acceptor levels, respectively, which eventually narrows the bandgaps of the semiconductors. Elements in Group IB (Cu, Ag, and Au) of the periodic table, which possess low solubility and self-compensation, can be used as acceptors for p-type ZnO.…”

Photoelectrochemical reduction of CO2 catalyzed by a 3D core–shell NiMoO4@ZnO heterojunction with bicentre at the (111) plane and thermal electron assistance

“…41–44 However, ZnO has some drawbacks, such as a large band gap of 3.2 eV limiting the harvesting of visible light and severe photocorrosion. 45,46…”

“…[41][42][43][44] However, ZnO has some drawbacks, such as a large band gap of 3.2 eV limiting the harvesting of visible light and severe photocorrosion. 45,46 NiMoO 4 is a stable monoclinic crystal structure and easy to obtain. The nickel molybdate is a p-type semiconductor with a layered structure and proper band-gap (2.54-2.9 eV).…”