Mass production of a single-atom cobalt photocatalyst for high-performance visible-light photocatalytic CO2 reduction

Abstract

The photocatalytic reduction of carbon dioxide (CO₂RR) into value-added chemical products is a promising way to enrich energy supply and reduce CO₂ emission. The proposal of a high-efficiency, low-cost and easy-to-operate photocatalyst is an essential segment for promoting the CO₂RR from small-scale laboratory examination to large-scale industrial application. Herein, we first come up with a Co photocatalyst with isolated Co single atoms anchored on a commercial super conductive carbon black (Co-SA@SP-800) and employ it to effectively boost the photocatalytic CO₂ reduction reaction. Large scale production of the Co-SA@SP-800 catalyst can be achieved by a simple and practical adsorption–pyrolysis method. The as-prepared Co-SA@SP-800 catalyst presents remarkable photoactivity and CO selectivity with a CO production yield of 1.64 × 10⁴ μmol g⁻¹ and a CO selectivity of 84.2% after 2 h of UV illumination in a heterogeneous system, and significantly outperforms other reference samples and most of the other efficient photocatalysts reported recently toward the conversion of CO₂. In situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was carried out to investigate the reaction intermediates during the photocatalytic CO₂RR. Control experiments and theoretical calculations revealed that the isolated single atomic Co–N₄ sites greatly lower the energy barrier for the desorption of CO* during CO₂-to-CO conversion, while suppressing H₂ evolution in the competing water splitting reaction. This work provides valuable new insights for rationally designing and synthesizing high-performance single atom catalysts for photocatalytic CO₂ reduction with ease of large-scale production.