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Co-existing air pollutants, especially NO x and VOCs, will generate secondary photochemical pollution under light irradiation. However, simultaneous elimination of multi-pollutants has long been a challenge. Photocatalysis could turn the reaction pathway between pollutants to convert them into harmless products, which is a promising technology for multi-pollutant control. Here we achieved synergistic photocatalytic degradation of NO and C 7 H 8 on InOOH photocatalyst, and the performance can be adjusted by H 2 O through affecting the interaction between surface species and catalyst. In situ DRIFTS and GC-MS revealed that the improved efficiency originated from the fast conversion of C–N coupling intermediates led by additional H 2 O. Surface characterizations and DFT simulation determined that accumulated nitrates will compete with the adsorption of NO and C 7 H 8 , resulting in a decline in efficiency in the later stage. Although improved efficiency would bring more nitrates, as H 2 O has comparable adsorption to nitrate at the same site, high humidity can mitigate the deactivation. The photocatalyst can be also simply regenerated by water washing. This work reveals the complex interaction in the multi-pollutant system and provides guidelines for precisely regulating the synergistic removal of NO x and VOCs. [Display omitted] • Synergistic removal of NO x and C 7 H 8 are achieved on InOOH. • H 2 O has a promotion effect on the simultaneous degradation of NO and C 7 H 8. • The enhanced removal originated from the fast conversion of C–N species. • The nitrate would compete with NO and C 7 H 8 adsorption and is the deactivation factor. • H 2 O has comparable adsorption to nitrate at the same site, thus can mitigate the decline in efficiency. [ABSTRACT FROM AUTHOR]

NO x and VOCs are primary air pollutants and their photochemical reactions would generate secondary pollutants like O 3 with NO 2 intermediate as the direct precursor. Here we apply a highly efficient In(OH) 3 photocatalyst to degrade mixed NO and C 7 H 8 for inhibition of photochemical O 3 generation. The dual pollutants show synergistic interaction from the adsorption process to photocatalytic reaction. C 7 H 8 and NO exhibit non-competitive adsorption and coupling reaction effects on In(OH) 3 surface. The coupling intermediate C 7 H 7 NOH would be oxidized to nitrotoluene and further decomposed into CO 2 and nitrates. Meanwhile, the protons and electrons released during the oxidation of C 7 H 8 can reduce NO to NH 4 +. Gibbs free energy calculation reveals that the coupling and reduction reactions are more favorable than the oxidation of NO to NO 2. The new conversion path of NO on In(OH) 3 when C 7 H 8 coexists could enable an increase of NO conversion efficiency to 100.0% and a decrease of NO 2 selectivity to only 3.7%, thus highly inhibiting the formation of O 3. [Display omitted] [ABSTRACT FROM AUTHOR]

Aromatic hydrocarbon is a representative type of VOCs, which causes adverse effects to human health. The degradation stability of aromatic hydrocarbon is of vital importance to commercializing a photocatalyst for its practical application. The most commonly used titanium dioxide photocatalyst (P25) was deactivated rapidly in the photocatalytic VOCs degradation process. In this work, the indium hydroxide (In(OH) 3) photocatalyst was developed, which exhibited not only higher efficient activity but also ultra-stable stability for degradation of benzene, toluene and their mixtures. The origin of the activity difference between two catalysts was investigated by combined experimental and theoretical ways. Based on in situ DRIFTS and GC-MS, it was revealed that benzoic acid and carbonaceous byproducts were specifically formed and accumulated on P25, which were responsible for deactivation of photocatalyst. In contrast, as revealed by both DFT calculations and experimental results, the reaction pathway with byproducts blocking the active sites can be thermodynamically avoided on In(OH) 3. This rendered high durability to In(OH) 3 photocatalyst in degradations of aromatic pollutants. The elucidation of deactivation-resistant effect and reaction mechanism as an ideal photocatalyst for practical usage were provided. [Display omitted] • Durable photocatalytic decomposition of VOCs was achieved on In(OH) 3. • The benzoic acid and carbonaceous byproducts were accumulated on P25. • The reaction pathway with byproducts can be avoided on In(OH) 3. • The reaction mechanisms of photocatalytic decomposition of VOCs was proposed. • The elucidation of deactivation-resistant mechanism on In(OH) 3 were proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Delocalized electrons were formed on Bi 2 O 2 CO 3 surface by interlayer hydrogenation. • Stable conjugated structure of benzene-ring was tailored, resulting in destabilization. • Direct ring-opening pathway and deep toluene oxidation were achieved. • The reaction pathway of reactants with un-activated benzene-ring was revealed. The stable conjugated structure of benzene-ring poses the persistent challenge for deep oxidation of toluene. In this study, the electronic structure of benzene-ring-containing reactants is tailored by engineering the interlayer hydrogenation in layered Bi 2 O 2 CO 3 , where charge separation and migration capabilities are improved and the confined charge in the interlayer and intralayer could transfer to catalyst surface and serve as delocalized electrons. The ring-opening site, the C = C bond, is activated by delocalized electrons. Consequently, the conjugated structure of the benzene-ring turns into a state with uneven charge distribution, resulting in weakened stability. With the attack of photo-generated radicals, the destabilized benzene-ring structure can be destroyed with direct ring-opening of toluene and achieves deep oxidation of toluene. Therefore, the degradation and mineralization of photocatalytic toluene are improved with great stability and humidity adaptability. This concept of promoting ring-opening with delocalized electrons provides a new strategy for the development of high-performance photocatalyst. [ABSTRACT FROM AUTHOR]