Research Article Cite This: ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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Highly Efficient Photoelectrochemical Reduction of CO2 at Low Applied Voltage Using 3D Co-Pi/BiVO4/SnO2 Nanosheet Array Photoanodes Li-Xia Liu,† Jiaju Fu,† Li-Ping Jiang,† Jian-Rong Zhang,*,† Wenlei Zhu,*,‡ and Yuehe Lin*,‡ †
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State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, P. R. China ‡ School of Mechanical and Materials Engineering, Washington State University, Pullman, Washington 99164, United States S Supporting Information *
ABSTRACT: To solve the increasing level of carbon dioxide (CO2) in the atmosphere, the bismuth vanadate (BiVO4)-based photoanode for photoelectrochemical (PEC) water oxidation has been considered as a promising candidate of power supply for CO2 reduction because of its low price and relatively narrow band gap. Nevertheless, the PEC capability of BiVO4 photoelectrodes is restricted by the short carrier diffusion length, undesirable electron transport ability, and slow oxygen evolution rate. To overcome these shortcomings, we design and fabricate a novel ternary hybrid composite of 3D Co-Pi/BiVO4/SnO2 nanosheet array (NSA) photoanodes. Benefiting from the high light-harvesting ability of NSAs, effective separation of electron−hole pairs for the BiVO4/SnO2 heterojunction, and fast water oxidation rate of Co-Pi, the hybrid system exhibited 20.2-times enhancement in photocurrent and a significant cathodic shift about the onset potential of water oxidation reaction compared with single BiVO4. Coupled with the Au nanoparticle cathode, the PEC cell exhibited a 90.0% faradaic efficiency for CO2 reduction under a small applied voltage of 1.10 V and saved more than 50% of electric energy compared to the general electrochemical cell. We believe that the fabricated 3D Co-Pi/BiVO4/SnO2 NSAs with remarkably enhanced PEC performance could provide clean power for the modern society via reduction reaction on pollution gases. KEYWORDS: photoelectrochemical, carbon dioxide reduction, BiVO4, SnO2, nanosheet arrays
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potential and improve the photocurrent.9,11,12 To improve light absorption, nanostructure engineering has been applied to BiVO4 fabrication.13−17 Under efficient light absorption of the BiVO4 photoanode, more electron−hole pairs could be generated. For preventing electron−hole pair recombination of BiVO4 electrodes, efforts have been made such as doping elements18,19 and constructing heterojunctions.20−22 On the other hand, modifying cocatalysts on the BiVO4 surface could also accelerate water oxidation reactions at the semiconductor surface.23−25 Recently, researchers have attempted to design novel strategies of ternary hybrid composites for photoanode fabrication to improve the PEC water oxidation performance of the BiVO4 electrode. Tang et al. reported a triple combination of the Co-Pi/BiVO4/ZnO nanorod photoanode for water oxidation, which achieved high light adsorption, efficient charge separation, and fast chemical reaction at the catalyst surface.26 Following the analogous strategy, efficient water splitting was performed using Fe(Ni)OOH/Mo:BiVO4/ SnO2−Pt nanocones,9 Co-Pi/BiVO4/TiO2-fluorine doped tin
INTRODUCTION Energy crisis and global warming have been recognized as urgent issues for modern society.1 Photoelectrochemical (PEC) CO2 reduction (CO2R) provides a promising solution for both the issues.2−4 A typical PEC CO2R system consists of an anode for energy generation and a cathode for CO2R. Unlike the traditional electrochemical (EC) cell that suffers from high overpotential because of the sole use of oxygen evolution catalysts as the anode, the proposed system is expected to be more efficient under solar irradiation.5,6 As one of the most prospective photoanode materials, BiVO 4 possesses a suitable band gap (2.4−2.6 eV) that permits effective light harvesting. It also has a much more positive valence band (VB) than 1.23 V versus reversible hydrogen electrode (RHE), suggesting large driven force for water oxidation to oxygen.7,8 However, the performances of BiVO4 are still limited by its short carrier diffusion length (
