Size dependence of photocatalytic oxidation reactions of Rh nanoparticles dispersed on (Ga1-xZnx)(N1-xOx) support

Abstract

Mixed Ga-Zn oxynitrides were synthesized using coprecipitation, wet-precipitation, and solid-solution methods. The oxynitrides were used as supports for Rh nanoparticle catalysts in photocatalytic water splitting, CO oxidation, and H2 oxidation. Mixed Ga-Zn oxynitrides produced by wet precipitation and nitridation had good visible-light-absorption properties and high surface areas, so they were used to support uniformly sized poly(vinylpyrrolidone)-stabilized Rh nanoparticles. The nanoparticle size range was 2-9 nm. These catalysts had negligible activity in photocatalytic H2 production by water splitting with methanol as a sacrificial agent. Other mixed Ga-Zn oxynitrides were also inactive. A reference sample provided by Domen also showed very low activity. The influence of particle size on Rh-catalyzed oxidation of CO and H2 was investigated. For CO oxidation, the activities of small particles were higher for particles with higher Rh oxidation degrees. The opposite holds for H2 oxidation.

Applications of Rhodium and Ruthenium Catalysts for CO Oxidation: an Overview

“…4 can also appear because they are very sensitive to the stoichiometry of reactant elements in their synthesis at the heating and cooling rates. The reason behind for increases the catalytic activity due to an improved specific surface area, lattice oxygen mobility and pore volume of the catalysts (Automobile and carbon monoxide, n.d.; Dey et al, 2017a;Dey et al, 2017b;Dey et al, 2017c;Dey et al, 2017d;Dey et al, 2018a;Dong et al, 2015;Dey et al, 2018b;Singh & Prasad, 2014;Solsona et al, 2004;Toyoshima et al, 2013;Goodman et al, 2007; (Cotton, 2013) 2009; Adeyemo et al, 2011;Teoh et al, 2015;Chen & Lin, 2015;Cominos et al, 2005;Snytnikov et al, 2003;Nehasil et al, 1996;Zhang et al, 2014;Hebben et al, 2010;Gao et al, 2013;Hulteberg et al, 2005;Wong et al, 2014;Dulaurent et al, 2000;Jung et al, 2007;Nishibayashi et al, 1997;Goerke et al, 2004;Brewster et al, 2014;Piccolo et al, 2016;Dey & Dhal, 2020a;Filot et al, 2011;Saadatjou et al, 2014;Song et al, 2004;Olveira et al, 2014).…”

“…The CO oxidation over Ru nano-particles represents the size dependence on catalytic activity. The small size of Rh/Ru nanoparticles show diffraction lines corresponding to the hexagonal close-packed structure, whereas the bigger nano-particles show the mixed phase of face-centered cubic and hexagonal close-packed structures (Zhang et al, 2014). The role of Rh/Ru surface oxide layer adjoining the metal core has been suggested as the catalytically active species.…”