Cu2o/Nanocarbon Architectures for Photoelectrochemical CO2 Conversion: Synthetic Aspects and Structure-Property Relationships

Abstract

Carbon nanomaterials, especially carbon nanotubes and graphene (either alone, or as building blocks of organized 3-D superstructures), are attracting significant attention as large surface area electrode support materials. Their composites with both inorganic and organic semiconductors represent an interesting class of new functional materials. In the first part of my talk I will briefly focus on the use of electrosynthetic (and photoelectrosynthetic) methods for preparing semiconductors on nanocarbon-modified electrode surfaces.1,2I will show how electrodeposition can be used to tune composition, crystal structure, and morphology of the nanocomposites for targeted applications. In the second part of my talk, selected examples will be given for how these electrosynthesized hybrid assemblies can be deployed in photoelectrochemical CO2 conversion. Given that CO2 is a greenhouse gas, using sunlight to convert CO2 to transportation fuel (such as methanol) represents a value-added approach to the simultaneous generation of alternative fuels and environmental remediation of carbon emissions from the continued use of conventional fuels.3 I will present the controlled synthesis and photoelectrochemical behavior of Cu2O/CNT4 and Cu2O/3D graphene composites for the CO2 reduction application. A carefully designed, multiple-step electrodeposition protocol was developed that ensured homogeneous coating of the CNTs with the Cu2O nanocrystals. This enhanced charge transport property for the hybrids resulted in a drastic increase in the photocurrents measured for the CO2 reduction. In addition to this superior performance, long term photoelectrolysis measurements proved that the Cu2O/CNT hybrids were more stable than the oxide alone. Structure property relationships will be shown, which may act as guidelines for the rational design of nanocomposite photoelectrodes. Figure 1. Illustration of the structure of the Cu2O/CNT composite and the increasing photocurrent with the increasing CNT-content. [1] C. Janáky and K. Rajeshwar: The Role of (Photo)electrochemistry in the Rational Design of Hybrid Conducting Polymer / Semiconductor Assemblies: From Fundamental Concepts to Practical Applications, Prog Pol Sci, 43 (2015) 396-435 [2] C. Janáky, E. Kecsenovity, K. Rajeshwar: Electrodeposition of Inorganic Oxide/ Nanocarbon Composites: Opportunities and Challenges, ChemElectroChem, 3 (2016) 181-192 [3] G. Ghadimkhani, N. R. De Tacconi, W. Chanmanee, C. Janaky, K. Rajeshwar: Efficient solar photoelectrosynthesis of methanol from carbon dioxide using hybrid CuO/Cu2O semiconductor nanorod arrays, Chem. Commun. 49 (2013) 1297–1299 [4] E. Kecsenovity, B. Endrődi, Z. Pápa, K. Hernádi, K. Rajeshwar, C. Janáky: Decoration of ultralong carbon nanotubes with Cu2O nanocrystals: a hybrid platform for enhanced photoelectrochemical CO2 reduction, J Mater Chem A, 4 (2016) 3139-3147 Figure 1