Lattice-strained nanotubes facilitate efficient natural sunlight-driven CO 2 photoreduction

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hool of Environment and Energy, Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling, South China University of Technology, Guangzhou 510006, China 2 Guangdong Engineering and Technology Research Center for Environmental Nanomaterials, The Key Laboratory of Pollution Control and Ecosystem Restoration in Industry Clusters (Ministry of Education), Guangzhou 510006, China § Shujie Liang and Xueming Liu contributed equally to this work. © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 22 September 2020 / Revised: 16 November 2020 / Accepted: 19 November 2020

ABSTRACT Photocatalytic reduction of CO2 holds tremendous promise for alleviating the energy crisis. Despite the progress that has been made, there are still some challenges to overcome, such as the realization under real sunlight rather than the simulation condition. In this work, ultrathin Ni2(OH)(PO4) nanotubes (NTs) prepared through hydrothermal route are applied as a novel catalyst for photocatalytic reduction of CO2 under real sunlight. The prepared Ni2(OH)(PO4) NTs exhibit a 11.3 µmol·h−1 CO production rate with 96.1% CO selectivity. Interestingly, Ni2(OH)(PO4) NTs have a positive impact on the facilitation of photoreduction in diluted CO2. Notably, when the system is performed under real sunlight, Ni2(OH)(PO4) NTs afford an accumulated CO of ca. 26.8 μmol with 96.9% CO selectivity, exceeding most previous inorganic catalysts under simulated irradiation in the laboratory. Our experimental results demonstrate that the multisynergetic effects induced by surface-OH and the lattice strain serve as highly active sites for CO2 molecular adsorption and activation as well as electron transfer, hence enhancing photoreduction activity. Therefore, this work provides experimental basis that CO2 photocatalysis can be put into practical use.

KEYWORDS CO2 photoreduction, diluted CO2, lattice strain, natural sunlight, application

1

Introduction

Heavy reliance on fossil fuels results in ever-increasing CO2 emission and then causes energy crisis and global environmental burden [1]. Converting the “waste” CO2 into valuable chemicals by the photocatalytic process shows great promise for simultaneously alleviating energy and environmental troubles [2, 3]. Despite the progress that has been made, there are still some challenges to overcome. Firstly, the CO2 conversion efficiency is still fairly low due to their thermodynamical stability with high dissociation energy of the C=O bond (ca. ~ 750 kJ·mol−1) [4]. Then, the sluggish kinetic process with multielectron reaction and protons transfer process greatly impede the selectivity of a specific product among many possible reaction species [5]. Moreover, most works require high purity gases for facilitating CO2 adsorption and activation [6]. In this case, utilizing a low concentration of CO2 directly by photocatalysis could be a promising energy-saving method [7]. Last but not least, low conversion efficiency and the required special devices during