Engineering a Kesterite-Based Photocathode for Photoelectrochemical Ammonia Synthesis from NOx Reduction

Shujie Zhou; Kaiwen Sun; Cui Ying Toe; Jun Yin; Jialiang Huang; Yiyu Zeng; Doudou Zhang; Weijian Chen; Omar F Mohammed; Xiaojing Hao; Rose Amal

doi:10.1002/adma.202201670

Engineering a Kesterite-Based Photocathode for Photoelectrochemical Ammonia Synthesis from NO_x Reduction

Adv Mater. 2022 Jul;34(29):e2201670. doi: 10.1002/adma.202201670. Epub 2022 Jun 11.

Authors

Shujie Zhou¹, Kaiwen Sun², Cui Ying Toe^{1

3}, Jun Yin⁴, Jialiang Huang², Yiyu Zeng², Doudou Zhang⁵, Weijian Chen², Omar F Mohammed³, Xiaojing Hao², Rose Amal¹

Affiliations

¹ School of Chemical Engineering, UNSW Sydney, Sydney, NSW, 2052, Australia.
² School of Photovoltaic and Renewable Energy Engineering, UNSW Sydney, Sydney, NSW, 2052, Australia.
³ School of Engineering, University of Newcastle, Callaghan, NSW 2308, Australia.
⁴ Advanced Membranes and Porous Materials Center, KAUST Catalysis Center, Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Kingdom of Saudi Arabia.
⁵ School of Engineering, The Australian National University, Canberra, ACT, 2601, Australia.

PMID: 35606154
DOI: 10.1002/adma.202201670

Abstract

Ammonia is a key chemical feedstock for industry as well as future carbon-free fuel and transportable vector for renewable energy. Photoelectrochemical (PEC) ammonia synthesis from NO_x reduction reaction (NO_x RR) provides not only a promising alternative to the energy-intensive Haber-Bosch process through direct solar-to-ammonia conversion, but a sustainable solution for balancing the global nitrogen cycle by restoring ammonia from wastewater. In this work, selective ammonia synthesis from PEC NO_x RR by a kesterite (Cu₂ ZnSnS₄ [CZTS]) photocathode through loading defect-engineered TiO_x cocatalyst on a CdS/CZTS photocathode (TiO_x /CdS/CZTS) is demonstrated. The uniquely designed photocathode enables selective ammonia production from NO_x RR, yielding up to 89.1% Faradaic efficiency (FE) (0.1 V vs reversible hydrogen electrode (RHE)) with a remarkable positive onset potential (0.38 V vs RHE). By tailoring the amount of surface defective Ti³⁺ species, the adsorption of reactant NO₃ ^- and ^* NO₂ intermediate is significantly promoted while the full coverage of TiO_x also suppresses NO₂ ^- liberation as a by-product, contributing to high ammonia selectivity. Further attempts on PEC ammonia synthesis from simulated wastewater show good FE of 64.9%, unveiling the potential of using the kesterite-based photocathode for sustainably restoring ammonia from nitrate-rich wastewater.

Keywords: NOx reduction; TiOx; ammonia synthesis; defect engineering; kesterite photocathodes.

Abstract

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