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The tannic acid induced assembly strategy was used to synthesize the Ni-doped SnO 2 nanosheets. The fabricated TA-Ni/SnO 2 sensors exhibited superior sensing performance to HCHO at working temperature of 80 °C (R a /R g = 184.3) and excellent sensing selectivity. The experimental and DFT results illustrated that the highly dispersed Ni substitution sites in SnO 2 crystals can be regarded as the active sites, which not only facilitated the generation of surface active O 2 –(ad) species, but also modified the electronic structure of SnO 2 crystals, contributing to superior sensing performance of TA-Ni/SnO 2 to HCHO. [Display omitted] • Tannic acid (TA) induced surface functional strategy is applied to synthesize Ni-doped SnO 2 nanosheets. • Ni ions can be highly dispersed on the SnO 2 nanosheets via TA. • The obtained materials exhibit superior sensing performance to HCHO. • The synergistic effects between O 2 –(ad) species and modified electronic structure contribute to the excellent sensing performance. Surface functionalization is a promising strategy to modulate the electronic and surface properties of metal oxide semiconductors. Here, we report a tannic acid (TA) induced surface functional strategy to synthesize Ni-doped SnO 2 nanosheets. Benefiting from the abundant polyphenolic and catechol groups, the linkage of TA not only exhibit high affinity to various substrate, but also show powerful chelating ability to metal ions. Hence, Ni ions can be highly dispersed on the SnO 2 nanosheets via TA, TA linkage also can prevent the aggregation of Ni ions during pyrolysis, and Ni substitution in SnO 2 crystals can be obtained. As a proof-of-concept demonstration, the TA-Ni/SnO 2 sensor is fabricated to detect HCHO, and exhibit superior sensing performance at low working temperature of 80 °C (R a /R g = 184.3), excellent sensing selectivity and long-term stability. Detail experimental and theoretical calculation demonstrate the highly dispersed Ni substitution active sites facilitate the generation of surface O 2 –(ad) species, and the electronic structure also can be modulated to exhibit high affinity to HCHO, hence, the synergistic effects contribute to the enhanced sensing performance. Our work paves the way for versatile surface functionalization to synthesize advanced materials for application in catalysis and sensing field. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dual functionalized Ni substitution in shuttle-like In 2 O 3 nanoparticles (NPs) has been synthesized. • The 2 wt% Ni-doped In 2 O 3 NPs exhibit high sensitivity (R a /R g = 2569.42 towards 50 ppm NH 3 at 140 °C), achieving 34 folds improvement compared with pristine In 2 O 3 NPs. • Ni substitution in rh-In 2 O 3 NPs can effectively modulate the electronic structure and surface acidity of material and further improve the adsorption of NH 3. • The substitution of Ni in rh-In 2 O 3 phase and surface O−(ad) species neighboring the substitution sites are recognized as the active sites. Hetero-atom doping is an effective way to improve the sensing performance of metal oxide semiconductor gas sensors. However, the synergistic effects generated from hetero-atom substitution in In 2 O 3 lattice and the relationship between the fine surface structure and sensing performance is still ambiguous. Here, Ni substitution in shuttle-like In 2 O 3 nanoparticles have been successfully synthesized, and the materials are fabricated as gas sensor to detect ammonia, which is a toxic molecule that is harmful for human healthy. We find the 2 wt% Ni-doped In 2 O 3 NPs exhibit high sensitivity (R a /R g = 2569.42 towards 50 ppm NH 3 at 140 °C), achieving 34 folds improvement compared with pristine In 2 O 3 NPs. The sensor also shows good long-term stability, high selectivity and fast response/recovery (23/10 s). Detail structural analysis illustrate the substitution of Ni in rh-In 2 O 3 phase and surface O−(ad) species neighboring the substitution sites are recognized as the active sites, and the reactive oxygen species and surface Bronster acidity can be dramatically enhanced after Ni modification, which contribute to the improvement of sensing performance. Our work illustrate the synergistic effects of hetero-atom doping on the sensing performance and pave the way for design of high performance sensing materials. [ABSTRACT FROM AUTHOR]