Hydrochar-Supported NiFe2O4Nanosheets with a Tailored Microstructure for Enhanced CO2Photoreduction to Syngas.

Abstract

Constructing high-efficiency composite photocatalysts with enhanced charge transfer and a rapid surface catalytic reaction has recently received significant attention. Herein, a hydrochar-mediated NiFe2O4 nanosheet (C/NFO) composite was rationally constructed by a simple hydrothermal method. Intimate interface contacts and chemical interactions between hydrochar and NFO were formed. The prepared C/NFO samples exhibited remarkable visible-light-driven catalytic CO2 reduction properties under mild reaction conditions with Ru(bpy)32+ sensitization. As the optimized sample, 16%-C/NFO achieved a 4-fold enhancement of CO production (17.49 μmol/h) compared with that of pure NFO. The C/NFO samples demonstrated good activity and structural stability in the CO2 photoreduction system. The carbon source of CO derived from CO2 was verified through isotopic labeling experiments using 13CO2. In situ photoluminescence and electrochemical characterizations confirmed the role of electron transfer intermediates of C/NFO. The synergistic effect of the nanosheet-like structure of NFO, combined with the surface functional groups of hydrochar, facilitated an exceptionally high rate of charge transfer and exposed abundant active adsorption sites for CO2, thereby promoting the efficient separation of photogenerated charge carriers and enhancing photocatalytic activity for CO2 reduction. This study presents a promising strategy for the rational design of hydrochar coupled with transition metal compound catalysts for efficient CO2 photoreduction.