Pd@H WO Nanowires Efficiently Catalyze the CO Heterogeneous Reduction Reaction with a Pronounced Light Effect.

The design of photocatalysts able to reduce CO to value-added chemicals and fuels could enable a closed carbon circular economy. A common theme running through the design of photocatalysts for CO reduction is the utilization of semiconductor materials with high-energy conduction bands able to generate highly reducing electrons. Far less explored in this respect are low-energy conduction band materials such as WO. Specifically, we focus attention on the use of Pd nanocrystal decorated WO nanowires as a heretofore-unexplored photocatalyst for the hydrogenation of CO. Powder X-ray diffraction, thermogravimetric analysis, ultraviolet-visible-near infrared, and in situ X-ray photoelectron spectroscopy analytical techniques elucidate the hydrogen tungsten bronze, H WO, as the catalytically active species formed via the H spillover effect by Pd. The existence in H WO of Brønsted acid hydroxyls OH, W(V) sites, and oxygen vacancies (V) facilitate CO capture and reduction reactions. Under solar irradiation, CO reduction attains CO production rates as high as 3.0 mmol g hr with a selectivity exceeding 99%. A combination of reaction kinetic studies and in situ diffuse reflectance infrared Fourier transform spectroscopy measurements provide a valuable insight into thermochemical compared to photochemical surface reaction pathways, considered responsible for the hydrogenation of CO by Pd@H WO.