Plasmon-assisted water splitting using two sides of the same SrTiO₃ single-crystal substrate: conversion of visible light to chemical energy.

A plasmon-induced water splitting system that operates under irradiation by visible light was successfully developed; the system is based on the use of both sides of the same strontium titanate (SrTiO3) single-crystal substrate. The water splitting system contains two solution chambers to separate hydrogen (H2) and oxygen (O2). To promote water splitting, a chemical bias was applied by regulating the pH values of the chambers. The quantity of H2 evolved from the surface of platinum, which was used as a reduction co-catalyst, was twice the quantity of O2 evolved from an Au-nanostructured surface. Thus, the stoichiometric evolution of H2 and O2 was clearly demonstrated. The hydrogen-evolution action spectrum closely corresponds to the plasmon resonance spectrum, indicating that the plasmon-induced charge separation at the Au/SrTiO3 interface promotes water oxidation and the subsequent reduction of a proton on the backside of the SrTiO3 substrate. The chemical bias is significantly reduced by plasmonic effects, which indicates the possibility of constructing an artificial photosynthesis system with low energy consumption.