Insights into Selective Mechanism of NiO-TiO₂ Heterojunction to H₂ and CO

Abstract

The construction of p-n heterojunctions has become a widely adopted strategy for achieving the selective detection of reducing gases, including H 2 and CO. Nevertheless, the elucidation of the gas selectivity mechanism at the nanoscale remains elusive. First-principle calculations provide an attractive avenue for comprehending the influence of coordination structures on gas-sensitive selectivity, thereby unveiling the structure−activity relationship of p-n heterojunction sites. In this study, we investigate the selective adsorption behavior of H 2 and CO on a NiO-TiO 2 heterojunction using density functional theory. The results of d-band center analysis confirm that the NiO-TiO 2 heterojunction with adsorbed oxygen significantly enhances the adsorption stability of reducing gases. Intriguingly, our calculations reveal that H 2 has a higher affinity for adsorbed oxygen on the heterojunction surface compared to that of CO, corresponding to a lower H 2 adsorption energy. Density of states (DOS) results indicate that the NiO-TiO 2 heterojunction, with preadsorbed oxygen, exhibits ultrahigh selectivity with an n-type gas-sensitive response to H 2 , effectively eliminating the cross-sensitivity observed with CO, as confirmed by gas-sensitive characterization research. The sensing mechanism of the NiO-TiO 2 heterojunction's selective detection of H 2 without interference from CO can be visually explained by electron transfer and potential barrier changes, paving the way for future developments in novel, selective gas-sensitive materials.

Metal-modified C3N1 monolayer sensors for battery instability monitoring

“…Initially, all gas molecules positioned 2.5 Å above the monolayer underwent structural optimization calculations to determine their equilibrium positions. Based on the positive correlation between the adsorption distance and energy, 50,51 the initial configurations following this criterion were selected, as illustrated in Fig. S15 and S16 †Fig.…”

Multi-atomic loaded C2N1 catalysts for CO2 reduction to CO or formic acid

“…Single-atom catalysts (SACs) with isolated transition metal (TM) atoms stabilized by carbon-based materials have attracted more and more attention due to their special electronic structure and platform utilization 12 and have become promising candidate materials in the nitrogen reduction reaction, 13 HER, 14–16 oxygen reduction reaction, 15,17 oxygen evolution reaction, 18,19 CO 2 RR, 20,21 and other reactions. 22 Previous studies have indicated that catalysts such as Mn, Mo, Ru, and Ti offer distinct advantages in the CO 2 RR compared to the HER, requiring lower overpotentials for the generation of intermediate products (*COOH or *OCHO). 23–29 Unfortunately, the stability of SACs is not satisfactory, 30 because when the bond of individual atoms to the carrier is weak, they tend to aggregate into nanoparticles, which inevitably affects their catalytic activity and further hinders their practical application.…”