Semiconductor-free nanoplasmonic photoelectrochemistry of H2O2 over Ag nanowires

Abstract Nanoplasmonics is currently experiencing an ongoing renaissance as a result of the booming research interest in LSPR-mediated but semiconductor-free photocatalysis and photoelectrochemistry directly over nanometals with excellent catalytic activity and conductive properties. To shed light on the underlying mechanism, the present study puts forward H₂O₂ as the probe molecule, with which the electroreduction at the phase boundary with photoexcited Ag nanowires (NWs) was systemically investigated. In particular, the reaction rate depends not only linearly on the illumination intensity but also on the resonant wavelength of the characteristic LSPR of the Ag NWs, evidently illustrating that the photoelectrochemical H₂O₂ reduction is mediated by the LSPR-induced energetic electrons of the Ag NWs. In addition to the mechanistic insights, the present study further highlights the great promise of such semiconductor-free LSPR-mediated photoelectrochemistry of H₂O₂ over Ag NWs in the analytical biochemistry field via proof-of-concept solar photoelectrochemical detection of ultradiluted H₂O₂ in PBS. The Ag NWs deposited on a carbon cloth substrate as the working electrode exhibit excellent sensitivity amounting to 118 μA cm⁻² mM⁻¹ under solar illumination, well outperforming that of the electrochemical counterpart measured in the dark by 50%.