Photocatalytic Reduction of CO2 to Methanol by Cu2O/TiO2 Heterojunctions

Abstract

The conversion of CO2 to low-carbon fuels using solar energy is considered an economically attractive and environmentally friendly route. The development of novel catalysts and the use of solar energy via photocatalysis are key to achieving the goal of chemically reducing CO2 under mild conditions. TiO2 is not very effective for the photocatalytic reduction of CO2 to low-carbon chemicals such as methanol (CH3OH). Thus, in this work, novel Cu2O/TiO2 heterojunctions that can effectively separate photogenerated electrons and holes were prepared for photocatalytic CO2-to-CH3OH. More visible light-active Cu2O in the Cu2O/TiO2 heterojunctions favors the formation of methanol under visible light irradiation. On the other hand, under UV-Vis irradiation for 6 h, the CH3OH yielded from the photocatalytic CO2-to-CH3OH by the Cu2O/TiO2 heterojunctions is 21.0–70.6 µmol/g-catalyst. In contrast, the yield of CH3OH decreases with an increase in the Cu2O fraction in the Cu2O/TiO2 heterojunctions. It seems that excess Cu2O in Cu2O/TiO2 heterojunctions may lead to less UV light exposure for the photocatalysts, and may decrease the conversion efficiency of CO2 to CH3OH.

Facile One-Pot Synthesis of CuxO/TiO2 Photocatalysts by Regulating Cu Oxidation State for Efficient Solar H2 Production

“…The characteristic absorption band at 560–700 nm observed for TiCu-2 to TiCu-4 is associated with the d–d transition of Cu 2+ . The peak broadening and shift of absorption edge to the visible region observed in Cu x O/TiO 2 are due to the intrinsic adsorption of copper oxides with a narrow band gap . The optical band gap ( E g ) energies of TiO 2 and Cu x O/TiO 2 samples were calculated using the Kubelka–Munk method, and the results are shown in Figure b and Table .…”

“…34 The peak broadening and shift of absorption edge to the visible region observed in Cu x O/TiO 2 are due to the intrinsic adsorption of copper oxides with a narrow band gap. 35 The optical band gap (E g ) energies of TiO 2 and Cu x O/TiO 2 samples were calculated using the Kubelka− Munk method, and the results are shown in Figure 3b and Table 1. The enlarged version of the Tauc plot is also shown in the inset of Figure 3b.…”

Photocatalytic conversion of carbon dioxide, methane, and air for green fuels synthesis

“…53 Since then, extensive research has been conducted on the implementation of TiO 2 in photocatalytic CO 2 reduction under visible and UV irradiation, starting with the investigation of pristine TiO 2 and its subsequent combination with diverse materials to assess the impact of metal doping. [54][55][56] A case study was conducted on a porphyrin-based MOF, where we observed a notable enhancement in the photocatalytic conversion of CO 2 to CH 3 OH when Cu 2+ was introduced. The presence of Cu 2+ resulted in a remarkable sevenfold increase in the rate of CH 3 OH production compared to the sample without Cu 2+ .…”

“…53 Since then, extensive research has been conducted on the implementation of TiO 2 in photocatalytic CO 2 reduction under visible and UV irradiation, starting with the investigation of pristine TiO 2 and its subsequent combination with diverse materials to assess the impact of metal doping. 54–56…”

Converting CO2 into Value‐Added Products by Cu2O‐Based Catalysts: From Photocatalysis, Electrocatalysis to Photoelectrocatalysis

“…Cu 2 O can be used as a co-catalyst or main catalyst to hybridize with other semiconductors, obtaining composite materials with multiple superior properties simultaneously. It is a "kill three birds with one stone" strategy to build heterojunction between p-type Cu 2 O and n-type semiconductor materials, such as TiO 2 , [139,140,[168][169][170] WO 3 , [142] Fe 2 O 3 , [171][172][173] Bi 2 Se 3 , [174] MnCo 2 O 4 [175] or WO 3 . [176,177] First, the carrier separation ability of Cu 2 O-based catalysts can be significantly improved.…”