# Light driven water oxidation on silica supported NiO–TiO2 heteronanocrystals yields hydrogen peroxide

## TL;DR

This study shows that light can drive water oxidation on silica-supported NiO–TiO2 nanocrystals to produce hydrogen peroxide efficiently.

## Contribution

A new photocatalytic system using NiO–TiO2 heteronanocrystals is introduced for efficient hydrogen peroxide production under light.

## Key findings

- NiO–TiO2 heteronanocrystals supported on silica produce H2O2 under light with an initial rate of 1.8 μmol g−1 min−1.
- Adding AgNO3 increases H2O2 production rates up to 9.1 μmol g−1 min−1 and steady-state concentrations to 174 μM.

## Abstract

Decomposition of nickel nitrate hexahydrate in the presence of rod-shape anatase TiO2 nanocrystals led to the formation of NiO–TiO2 heteronanocrystals confirmed with powder X-ray diffraction and electron microscopy. The heteronanocrystals were supported on amorphous fumed silica to provide a heterogeneous photocatalyst material SiO2/NiO–TiO2. The aqueous suspension of the catalyst, under argon atmosphere, irradiated with a Xe arc lamp led to the formation of H2O2 with trace gaseous product formation. We observed an initial rate of formation of H2O2 of 1.8 μmol g−1 min−1 that decays toward a steady-state concentration of 52 μM. Addition of AgNO3 to the aqueous suspension gave fast reduction of silver ion, and higher initial rates of formation and steady state concentrations of H2O2. We report the concentration dependence of water oxidation versus [AgNO3] with the fastest initial rate of formation of H2O2 as 9.1 μmol g−1 min−1 and a steady-state concentration of 174 μM.

Light illumination of aqueous suspensions of supported NiO–TiO2 heteronanocrystals led to water oxidation to form hydrogen peroxide.