A Schottky-Barrier-Free Plasmonic Semiconductor Photocatalyst for Nitrogen Fixation in a One-Stone-Two-Birds Manner

Plasmonic photocatalysis has received much attention owing to attractive plasmonic enhancement effects in improving the solar-to-chemical conversion efficiency. However, the photocatalytic efficiencies have remained low mainly due to the short carrier lifetime caused by the rapid recombination of plasmon-generated hot charge carriers. Although plasmonic metal-semiconductor heterostructures can improve the separation of hot charge carriers, a large portion of the hot charge carriers are lost when they cross the Schottky barrier. Herein, a Schottky-barrier-free plasmonic semiconductor photocatalyst, MoO3-x, which allows for efficient N-2 photofixation in a one-stone-two-birds manner, is demonstrated. The oxygen vacancies in MoO3-x serve as the stone. They kill two birds by functioning as the active sites for the chemisorption of N-2 molecules and inducing localized surface plasmon resonance for the generation of hot charge carriers. Benefiting from this unique strategy, plasmonic MoO3-x exhibits a remarkable photoreactivity for NH3 production up to the wavelength of 1064 nm with apparent quantum efficiencies over 1%, and a solar-to-ammonia conversion efficiency of 0.057% without any hole scavenger. This work shows the great potential of plasmonic semiconductors to be directly used for photocatalysis. The concept of the Schottky-barrier-free design will pave a new path for the rational design of efficient photocatalysts.

Automated summary

Plasmonic photocatalysis is attracting attention for improving solar-to-chemical conversion efficiency, but low efficiency remains a challenge. A Schottky-barrier-free plasmonic semiconductor photocatalyst, MoO3-x, was demonstrated for efficient N-2 photofixation, offering a new approach for solar-to-ammonia conversion efficiency.