Pressure-driven band gap engineering in ion-conducting semiconductor silver orthophosphateElectronic supplementary information (ESI) available: Morphology (SEM), elemental analysis (EDX), and malleability of the sample, pressure-dependent optical properties (Tauc plot), Raman spectra, synchrotron XRD spectra of pristine and quenched samples, typical Rietveld refinement results of the high-pressure phase, simulated XRD spectra, calculated volume-pressure plot and energy-volume plot, partial charg

• Main Authors: Lu, Yang, Zhu, Shengcai, Huang, Eugene, He, Yu, Ruan, Jiaji, Liu, Gang, Yan, Hao
• Format: Journal Article
• Language: English
• Published: 26.02.2019
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c8ta10606a

The obtainment of active semiconductor photocatalysts remains a challenge for converting sunlight into clean fuels. A pressing need is to explore a novel method to tune the electronic band structures and gain insightful knowledge of the structure-property relationships. In this work, taking silver orthophosphate (Ag 3 PO 4 ) as an example, a static pressure technique is applied to modulate the band gap and indirect-direct band character via altering its crystal structure and lattice parameters. Under ambient conditions, cubic Ag 3 PO 4 possesses an indirect-band gap of ∼2.4 eV. At elevated pressure, the band gap of Ag 3 PO 4 narrowed from 2.4 eV to 1.8 eV, reaching the optimal value for efficient solar water splitting. During the pressure-induced structural evolution from cubic to trigonal phases, the indirect-to-direct band gap crossover was predicted by first-principles calculations combined with structure search and synchrotron X-ray diffraction experiments. Strikingly, the observed band gap narrowing was partially retained after releasing pressure to ambient pressure. This work paves an alternative pathway to engineer the electronic structure of semiconductor photocatalysts and design better photo-functional materials. The obtainment of active semiconductor photocatalysts remains a challenge for converting sunlight into clean fuels. Here, a pressure technique is explored to optimize the electronic band structure of a promising photocatalyst.