Chitosan coated copper-oxide nano particles: a novel electro-catalyst for CO2 reduction

Abstract

We report here a simple one-pot method for the synthesis of copper-oxide based novel film forming electro catalysts for CO₂ reduction. Water dispersible chitosan (CS)–CuO/Cu₂O (Cu_xO) nano composites of diameter 10–20 nm were obtained by hydrothermal reactions of CS, CuSO₄·5H₂O and tartaric acid (TA). Here, TA acts as a multifunctional reagent as de-polymerizer of CS, ionic cross linker of depolymerised CS and complex forming ligand with Cu²⁺ ions. These CS coated Cu_xO nanoparticles were characterized by HRTEM, UV-VIS, AFM, FTIR and XPS. An ultra thin film of composite catalyst was deposited onto a Pt electrode by drop cast techniques and applied to study CO₂ reduction by cyclic voltammetric techniques. The voltammogram shows a reduction peak at −0.665 V vs. RHE at pH 5.3 with a short hydrogen evolution tail indicating its better performance in terms of retarding the H₂ evolution reaction. This has been explained proposing a model of protonated CS on the electrode surface that repels incoming H⁺ ions at the electrode–electrolyte interface. This is the first time a film forming copper-oxide based nano composite material for efficient electro-catalytic reduction of CO₂ in aqueous solution has been reported.