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Designing effective Si/Ag interface via controlled chemical etching for photoelectrochemical CO₂ reduction

Hu, Yongpan, Chen, Fengjiao, Ding, Pan, Yang, Hui, Chen, Junmei, Zha, Chenyang, Li, Yanguang
Journal of materials chemistry A 2018 v.6 no.44 pp. 21906-21912
carbon dioxide, cathodes, chemistry, electric current, hydrogen, ions, photosynthesis, semiconductors, silicon, silver, value added
Photoelectrochemical reduction of CO₂ to value-added chemicals represents a promising approach for artificial photosynthesis, but often suffers from limited selectivity and stability. Improving its performance would require proper design of semiconductor and co-catalyst materials, along with a strategy for effective coupling. Here, we report that controlled chemical etching of Si wafer by Ag⁺ ions yields effective semiconductor/co-catalyst interface for photoelectrochemical CO₂ reduction. Resultant photocathodes exhibit large photocurrent density (∼10 mA cm⁻² under 0.5 sun), great CO faradaic efficiency (90% at −0.5 V versus reversible hydrogen electrode), and impressive operational stability (little activity or selectivity loss within 8 h). Further enhancement (by ∼20%) of photocurrent density is achieved by combining photolithography patterning with chemical etching. Our study applies long-known chemistry as an unexpected solution and may provide a new strategy for high-performance photoelectrochemical CO₂ reduction.