Effect of bandgap alignment on the photoreduction of CO₂ into methane based on Cu₂O-decorated CuO microspheres

Abstract

Semiconductors' band gap alignment is important for the photoreduction of CO 2 to methane. In the paper, two kinds of Cu 2 O-decorated CuO microspheres composed with nanoflakes were prepared by using two different methods. Their electron behaviors were studied from the XPS spectra and photoelectrochemical measurements. Both samples are p-type CuO covered with an amount of Cu 2 O nanoparticles on their surface. Combined with their bandgaps and flat band potentials, CuO-Mic has a well-matched bandgap alignment between Cu 2 O and CuO, which is favorable for the separation of photogenerated electron-hole pairs. Those photogenerated carriers are beneficial for the conversion of CO 2 to CH 4 , as an 8-electron process for the conversion of CO 2 to CH 4 will consume more photogenerated electrons for the chemical reactions than that of the 2-electron process for CO 2 reduction to CO. Therefore, CuO-Mic has much better photocatalytic activity for CO 2 reduction to CH 4 with a CH 4 yield ten times higher than that of CuO-Hyd under a visible light irradiation, the CO yields of the CO 2 reduction are identical.

Light-driven carbon dioxide reduction over the Ag-decorated modified TS-1 zeolite

“…More importantly, the heterojunction between Cu 2 O and CuO could accelerate the separation of photoexcited electron–hole pairs. 29 Therefore, the composite of Cu 2 O and CuO is critical to the CO 2 reduction. The Ti2p peaks of the Cu-TS-1 and Ag/Cu-TS-1 samples can be deconvoluted into two peaks, i.e.…”

“…More importantly, the heterojunction between Cu 2 O and CuO could accelerate the separation of photoexcited electron-hole pairs. 29 Therefore, the composite of Cu 2 O and CuO is critical to the CO 2 reduction. The Ti2p peaks of the Cu-TS-1 and Ag/Cu-TS-1 samples can be deconvoluted into two peaks, i.e., the peaks at 464.71 and 459.01 eV reveal the existence of Ti 4+ species in the form of TiO 2 while the lower-energy peaks at 464.21 and 458.51 eV can be corresponded to Ti 3+ species.…”

Dual Heterojunction Graphene-Supported Photocatalysts of Copper Oxide Nanowires and Copper Ferrite Nanoparticles for Photoelectrochemical Water Splitting

“…3,4 Transition-metal-based materials is one type of promising HER catalyst candidates because not only of their high abundance in the Earth's crust, generally benign toxicity to the environment, and low cost but also of their outstanding electrical conductivity and superior chemical and thermal stability. 5 Among the transition metal oxides, cupric oxide (CuO) and cuprous oxide (Cu 2 O) have direct bandgaps of 1.2−1.7 eV 6 and 2.0−2.4 eV, 7 respectively, which cover the solar electromagnetic spectrum. Their small bandgaps also enable CuO and Cu 2 O to have strong photoabsorption, making them attractive photocatalysts for HER under sunlight irradiation.…”

“…In a photoelectrochemical (PEC) water splitting reaction, semiconductors harness solar energy to create electron–hole pairs, subsequently utilizing them to trigger a reaction with water to produce hydrogen as a clean, low cost, and eco-friendly energy resource. , As an appropriate choice of catalysts in a PEC cell for the half-cell hydrogen evolution reaction (HER) is crucial, the catalysts should broadly satisfy the following requirements: (1) a proper bandgap compatible with the solar electromagnetic spectrum (1.6–2.2 eV); (2) appropriate alignment of the band edge that covers the water redox potentials; (3) high energy conversion efficiency; (4) operational stability in the nominal environment; and (5) a naturally abundant material source with a low cost of production that is compatible with large-scale applications. , Transition-metal-based materials is one type of promising HER catalyst candidates because not only of their high abundance in the Earth’s crust, generally benign toxicity to the environment, and low cost but also of their outstanding electrical conductivity and superior chemical and thermal stability . Among the transition metal oxides, cupric oxide (CuO) and cuprous oxide (Cu 2 O) have direct bandgaps of 1.2–1.7 eV and 2.0–2.4 eV, respectively, which cover the solar electromagnetic spectrum. Their small bandgaps also enable CuO and Cu 2 O to have strong photoabsorption, making them attractive photocatalysts for HER under sunlight irradiation.…”

Role of TiO2 coating layer on the performance of Cu2O photocathode in photoelectrochemical CO2 reduction

“…Cu 2 O is considered one of the promising catalysts for highly efficient CO 2 reduction due to its appropriate bandgap (2-2.2 eV), negative enough conduction band position, and natural abundance for large-scale fabrication [9]. Varies products have been formed over Cu 2 O hitherto, like CH 3 OH, CH 4 and ethylene (C 2 H 4 ) [10][11][12][13][14]. However, as the common weakness for many efficient photoelectrodes, the instability issue makes it very easy for Cu 2 O to be decomposed.…”