The synthesis of Rh nanocatalysts with controllable morphology provides a feasible route for tuning their physicochemical characteristics, and thus directly affects their catalytic performances. Previous researches mainly focused on the development of Rh nanostructures with low-index surfaces such as cubes with {100} faces, plates and tetrahedrons with {111} faces. Limited reports spared attentions on the study of high-index and surface-defect-enriched nanocrystals owing to the involvement of high-energy surfaces and increased surface-to-volume ratios causing thermodynamics unfavorable. However, nanocrystals with defect-rich surfaces containing increasingly less coordinated surface atoms can benefit the interaction between the nanocrystal surface and the molecular adsorbates. Therefore, in this study, an aqueous synthesis of concave Rh nanotetrahedra (CTDs) with surface-defect-rich structures serving as efficient catalysts for energy conversion reactions is demonstrated. To investigate the growth kinetics and mechanism, the reduction of Rh ions follows a first-order reaction and the formation of CTDs is accordant with the four-step model of metallic nanoparticle growth. By tuning the surfactant concentration, the morphology of Rh CTDs evolve into highly excavated nanotetrahedra (HETDs) and twinned nanoparticles (TWs). In comparison with CTD surfaces, HETDs and TWs possess more regular surfaces with layered terraces. The catalytic performance of these three types of nanocrystals was evaluated by methanol electrooxidation and hydrogen evolution from hydrolysis of ammonia borane. The CTDs significantly showed the best catalytic performance owing to the defect-enrichment. In addition, both CTDs and HETDs have strong absorption near the visible light region (382 and 396 nm), and thus showed plasmon-enhanced performance in photocatalytic hydrogen evolution under irradiation of visible light. The CTDs also showed better photoactivity than that of HETDs, likely due to more pronounced LSPR hot spots. This facile synthesis of defect-rich Rh nanotetrahedra in aqueous system inspires to the fields of nanosynthesis and catalysis.

Aqueously synthesized concave Rh nanotetrahedra with defective surfaces for defect- and plasmon-enhanced catalytic energy conversion

256th National Meeting (2018)

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