Photocatalytic Activity of (Ga_1-xZn_x)(N_1-xO_x) for Visible-Light-Driven H₂ and O₂ Evolution in the Presence of Sacrificial Reagents

Abstract

The photocatalytic activity of (Ga1- x Zn x )(N1- x O x ), a solid solution of GaN and ZnO, for H2 and O2 evolution in the presence of methanol and silver nitrate as sacrificial reagents under visible light (λ > 420 nm) is investigated in detail. (Ga1- x Zn x )(N1- x O x ) evolves H2 from an aqueous methanol solution when loaded with nanoparticulate Rh2- y Cr y O3 as a cocatalyst, and evolves O2 from an aqueous silver nitrate solution without a cocatalyst. Structural analyses indicate that the H2 evolution activity is strongly dependent on the crystallinity and composition of the catalyst, while the rate of O2 evolution is proportionally related to the specific surface area. The activity for H2 evolution from methanol solution is of the same order as for overall water splitting, but is an order of magnitude lower than that for O2 evolution from silver nitrate solution. The results of photocatalytic reactions and photoelectrochemical measurements suggest that the rate-determining step for overall water splitting using (Ga1- x Zn x )(N1- x O x ) is the H2 evolution process.

Structural evolution in Pt/Ga-Zn-oxynitride catalysts for photocatalytic reforming of methanol

“…The results are summarized in the Supplementary Material (section S2). The band gap values derived from the UV-visible spectra were in agreement with those available in the literature [9,31].…”

“…However, this co-catalysts/semiconductor system is less effective in the methanol photocatalytic reforming reaction [31]. High temperature reduction of the metal precursor [32] in H 2 is one of the most commonly used methods to prepare supported metal catalysts, but it is believed unsuitable for oxynitrides because of their limited thermal stability compared to oxides [33].…”

Development of Novel Photocatalyst and Cocatalyst Materials for Water Splitting under Visible Light

“…Therefore, we conducted a systematic analysis of the dependence of the activities of GaN:ZnO for H 2 and O 2 evolution half reactions in the presence of sacrificial reagents on structural properties, and the results are compared to the data for overall water splitting. 53 GaN:ZnO evolved H 2 steadily from an aqueous methanol solution when loaded with a proper H 2 evolution cocatalyst, and evolved O 2 from an aqueous silver nitrate solution without the aid of a cocatalyst. Structural analyses indicated that the H 2 evolution activity depends strongly on the crystallinity and composition of GaN:ZnO, while the rate of O 2 evolution is proportionally related to the specific surface area.…”

Optical properties of oxynitride powders

“…Rh2-xCrxO3 was tested recently as nanoparticles. 35), 39) Many nitrides and oxynitrides belonging to various structuretypes have been tested separately for photoreduction and photooxydation reactions using sacrificial agents, respectively with methanol (electron donor) and silver nitrate (electron acceptor). For example, TaON and CaTaO2N manifest an activity for photoreduction and Ta3N5 and TaON, a strong activity for photooxydation.…”