Herein, the bimetallic Pd 3 In 1 alloy were deposited onto the crystal facet engineered TiO 2 nanosheet (NS) via one-step photoreduction (Pd 3 In 1 /TiO 2 -NS) for selective conversion of nitrate (NO 3 − ) to N 2 . Bimetallic Pd 3 In 1 provides higher affinity sites to bind NO 3 − and significantly reduces the energy barrier of the rate-limiting step (NO 3 * + e − → NO 2 *), which is the key for the ultra-fast NO 3 − reduction kinetics. More importantly, the synergistic effect of Pd and In not only suppresses the hydrogen evolution reaction resulting in high efficiency utilization of photogenerated electrons, but also promotes the selective conversion of nitrite (NO 2 − ) to N 2 . Consequently, Pd 3 In 1 /TiO 2 -NS exhibits 100 % NO 3 − conversion and 90 % N 2 selectivity within 20 min in six cycles. One order of magnitude improvement on the NO 3 − reduction kinetic constants of Pd 3 In 1 /TiO 2 -NS (0.254 min −1 ) is achieved compared with pristine TiO 2 -NS and monometallic loaded ones. This work provides new insights into the rational construction of bimetallic alloy cocatalysts for high-efficiency photocatalytic denitrification.
Pan Tian,Zhongjie Cai,Guowu Zhan,Jiale Huang,Qingbiao Li
The conversion of CO 2 into value-added chemicals is an effective way to mitigate the environmental problems caused by huge anthropogenic CO 2 emissions. Although In 2 O 3 /Pd catalyst possesses excellent catalytic performance in CO 2 hydrogenation to methanol, the formation of Pd-In alloy on the catalyst surface greatly reduces the yield of methanol. Herein, we adopt a natural biomaterial ( viz. , rape pollen) as a template to synthesize hierarchically structured bio-In 2 O 3 and bio-In 2 O 3 /Pd catalysts. In particular, we found that the pretreatment of pollen using hydrochloric acid (HCl) played a critical role in determining catalytic performance. A series of bio-In 2 O 3 were prepared by using the pollen templates with different etching degrees, and then the bio-In 2 O 3 -x/Pd catalysts (x denoted as the amount of HCl, mL) were prepared using an impregnation-reduction method. It was surprising that the CO 2 conversion of bio-In 2 O 3 –15/Pd catalyst was 8.2% with methanol selectivity of 74.7%, which was much better than the bio-In 2 O 3 –0/Pd (2.6% and 54.6%, respectively). The dramatic enhancement was due to that the acid-etched pollen template owns a hollow cage-like structure and abundant surface functional groups (-NH 2 and -COOH), which is beneficial to the growth of In 2 O 3 with a high amount of surface oxygen vacancies. Also, the bio-In 2 O 3 /Pd catalyst (prepared with untreated pollen template) was more prone to form Pd-In alloys as a result of the strong interaction between Pd with In 2 O 3 . In contrast, the In 2 O 3 spatial distribution of bio-In 2 O 3 –15/Pd was more uniform with an appropriate interaction of Pd with In 2 O 3 that inhibited the formation of Pd-In alloys. Even Pd loaded on commercial In 2 O 3 exhibited inferior performance (3.4% CO 2 conversion and 81% methanol selectivity) to bio-In 2 O 3 –15/Pd catalyst. Accordingly, the present work offers a green and efficient method to prepare supported In 2 O 3 /Pd catalysts by using the acid-etched pollen as a template.
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