Decoupling Strategy for Enhanced Syngas Generation from Photoelectrochemical CO2 Reduction

Sheng Chu; Pengfei Ou; Roksana Tonny Rashid; Pegah Ghamari; Renjie Wang; Hong Nhung Tran; Songrui Zhao; Huiyan Zhang; Jun Song; Zetian Mi

doi:10.1016/j.isci.2020.101390

Decoupling Strategy for Enhanced Syngas Generation from Photoelectrochemical CO₂ Reduction

iScience. 2020 Aug 21;23(8):101390. doi: 10.1016/j.isci.2020.101390. Epub 2020 Jul 20.

Authors

Affiliations

¹ Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, China; Department of Electrical and Computer Engineering, McGill University, 3480 University Street, Montreal, QC H3A 0E9, Canada. Electronic address: schu@seu.edu.cn.
² Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montreal, QC H3A 0C5, Canada.
³ Department of Electrical and Computer Engineering, McGill University, 3480 University Street, Montreal, QC H3A 0E9, Canada.
⁴ Key Laboratory of Energy Thermal Conversion and Control of Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, China.
⁵ Department of Mining and Materials Engineering, McGill University, 3610 University Street, Montreal, QC H3A 0C5, Canada. Electronic address: jun.song2@mcgill.ca.
⁶ Department of Electrical and Computer Engineering, McGill University, 3480 University Street, Montreal, QC H3A 0E9, Canada; Department of Materials Science and Engineering, University of Michigan, Ann Arbor, 1301 Beal Avenue, Ann Arbor, MI 48109, USA. Electronic address: ztmi@umich.edu.

Abstract

Photoelectrochemical CO₂ reduction into syngas (a mixture of CO and H₂) provides a promising route to mitigate greenhouse gas emissions and store intermittent solar energy into value-added chemicals. Design of photoelectrode with high energy conversion efficiency and controllable syngas composition is of central importance but remains challenging. Herein, we report a decoupling strategy using dual cocatalysts to tackle the challenge based on joint computational and experimental investigations. Density functional theory calculations indicate the optimization of syngas generation using a combination of fundamentally distinctive catalytic sites. Experimentally, by integrating spatially separated dual cocatalysts of a CO-generating catalyst and a H₂-generating catalyst with GaN nanowires on planar Si photocathode, we report a record high applied bias photon-to-current efficiency of 1.88% and controllable syngas products with tunable CO/H₂ ratios (0-10) under one-sun illumination. Moreover, unassisted solar CO₂ reduction with a solar-to-syngas efficiency of 0.63% is demonstrated in a tandem photoelectrochemical cell.

Keywords: Catalysis; Electrochemical Energy Conversion; Nanomaterials.