New Way for CO₂ Reduction under Visible Light by a Combination of a Cu Electrode and Semiconductor Thin Film: Cu₂O Conduction Type and Morphology Effect

Abstract

How to take advantage of CO 2 has been one of the main issues to be addressed around the world. Although there are many methods to convert CO 2 to organic fuel, the efficiency is still not high enough for practical application. Herein, we have accomplished better conversion of CO 2 by the combination of metal electrode and semiconductor thin films responsive to visible light. First, the deposition of p-type and n-type Cu 2 O thin films onto a Cu substrate is successfully achieved. Then, the prepared Cu/Cu 2 O samples are used for catalytic reduction of CO 2 in photoelectrochemical systems in comparison with that in photochemical and electrochemical systems. The results show that CH 4 and C 2 H 4 are the major hydrocarbon gas products, and the prepared Cu/Cu 2 O samples have much higher selectivity for C 2 H 4 formation compared with the pure Cu electrode. The best yield for CO 2 reduction is obtained in the photoelectrochemical system under visible light. Additionally, CO 2 conversion efficiency over the Cu/Cu 2 O (p-type) electrode is much higher than that over Cu/Cu 2 O (n-type) with similar morphology. The morphology of Cu 2 O has an effect on the CO 2 reduction activity in the photoelectrochemical system as well. The related mechanism is discussed in detail especially for the reaction in the beginning 15 min. The study will provide us a new way to utilize solar light for efficient conversion of CO 2 into organic fuel.

Light-Driven Heterogeneous Reduction of Carbon Dioxide: Photocatalysts and Photoelectrodes

“…Additionally, thin films of electrodeposited Cu 2 O were used as CO 2 reduction catalysts under illumination from a blue LED (435−450 nm). 212 Methane and ethane were found to be the major products, with the current efficiency of ethane approaching 33% for a p-type sample of Cu 2 O. Nonetheless, an extremely negative potential had to be applied (−2.0 V vs Ag/AgCl) to obtain such yields.…”

Semiconductor‐Based Photoelectrochemical Conversion of Carbon Dioxide: Stepping Towards Artificial Photosynthesis

“…Ba et al. experimented with the two types of electrodes, which demonstrated much higher CO 2 conversion efficiency over the Cu/p‐Cu 2 O electrode, especially in the conversion to C 2 H 4 . A basic study of copper oxide nanoparticles on a copper electrode (Cu/Cu 2 O) mapped the product evolution profiles, including methanol, ethanol, formaldehyde, acetaldehyde, and acetone, as a function of bias potential, electrolysis time, and pH.…”

“…The morphology of the deposited layer will also make a difference. In the case above, stonelike Cu 2 O exhibited a better performance than that of Cu 2 O nanobelt arrays, mainly owing to the high coverage and amount of Cu 2 O on the Cu substrate . Similarly, if Cu 2 O crystallites were electrodeposited outside CuO, the p‐type CuO/Cu 2 O core–shell structure photocathode successfully resulted in methanol being produced from CO 2 reduction, with FE>90 % at potentials of 800 mV below the thermodynamic value …”

Sustainable Recovery of CO2 by Using Visible-Light-Responsive Crystal Cuprous Oxide/Reduced Graphene Oxide

“…In the earlier report [38], the different facets of Cu 2 O were investigated to perform the photocatalytic reduction of CO 2 , indicating that the low-index facets of Cu 2 O possessed higher activity than Cu 2 O with higher index facets. In addition, Cu 2 O with a stone-like shape exhibited superior activity to that with nanobelt arrays in terms of CO 2 photoreduction [39]. Nevertheless, the crystal Cu 2 O applied in the photocatalytic reactions suffers from the separation of photogenerated electron-hole pairs [31] and long-term stability [40].…”