Two-dimensional forms of robust CO2 reduction photocatalysts

Steven B Torrisi,Joseph H Montoya,Arunima K Singh,Tathagata Biswas,Kristin A Persson

doi:10.1038/s41699-020-0154-y

Abstract

Photoelectrocatalysts that use sunlight to power the CO2 reduction reaction will be crucial for carbon-neutral power and energy-efficient industrial processes. Scalable photoelectrocatalysts must satisfy a stringent set of criteria, such as stability under operating conditions, product selectivity, and efficient light absorption. Two-dimensional materials can offer high specific surface area, tunability, and potential for heterostructuring, providing a fresh landscape of candidate catalysts. From a set of promising bulk CO2 reduction photoelectrocatalysts, we screen for candidate monolayers of these materials, then study their catalytic feasibility and suitability. For stable monolayer candidates, we verify the presence of visible-light band gaps, check that band edges can support CO2 reduction, determine exciton binding energies, and compute surface reactivity. We find visible light absorption for SiAs, ZnTe, and ZnSe monolayers, and that due to a lack of binding, CO selectivity is possible. We thus identify SiAs, ZnTe, and ZnSe monolayers as targets for further investigation, expanding the chemical space for CO2 photoreduction candidates.

Highlights

Efficient, stable, scalable photoelectrocatalysts (PECs) which convert sunlight and CO2 into useful products provide a desirable path towards achieving society’s urgent carbon-neutral energy goals[1,2]
Previous experimental and theoretical works have investigated the structural, electronic, and chemical characteristics of a few monolayer phases of GaSe22, GaTe23, ZnSe19,24–32, ZnTe29,30,32, and SiAs33–35. 2D layers of ZnSe in various structural forms have attracted attention for their photoabsorption properties[24,36], as have low-dimensional forms of ZnTe bound to nanowires or in nanoparticle form[37,38,39]
The HSE06 hybrid exchangecorrelation functional[47,48] is known to exhibit an improved treatment of semiconductor bandgaps: in Fig. 4, we show that the band gaps of the 2D materials computed using HSE06 lie mostly within the visible light spectrum, and the band edges are appropriate for CO2 reduction

Summary

Introduction

Stable, scalable photoelectrocatalysts (PECs) which convert sunlight and CO2 into useful products provide a desirable path towards achieving society’s urgent carbon-neutral energy goals[1,2]. Three example applications of CO2 reduction products include (i) short-term storage of solar energy using methane[3], which forms a basis for decentralized solar electricity generation,. (ii) generating syngas mixtures of CO and H2 as feedstocks for the Fischer–Tropsch process[4], or (iii) decreasing the carbon footprint of current industrial processes through efficient production of widely used feedstocks like formic acid. Efficient electrochemical reduction of CO2 requires catalysts which can survive a strongly reducing environment and provide product selectivity at low overpotentials with respect to the complete reaction pathway[5]. Photoelectrocatalysts must clear all the same hurdles while still efficiently capturing light and providing photoexcited electrons at the appropriate CO2 reduction energy. The search for CO2 reduction PECs is an active and challenging area of research

Methods

Results

Conclusion