With the rapid development of industry, water remediation has attracted increasingly attention from scientific researchers. Particularly, the catalytic reduction of 4-nitrophenol (4-NP) to 4-nitroaniline is extremely significant, due to the pollutant characters of the former and industrial applications of the latter. Though bitransition metal Cu-based catalysts have shown high activity, the construction of hierarchical catalysts with both high activity and stability via a facile strategy is still a huge challenge. Here, series of nanosheet array-like composites xCu@Cu2O-CuNiAl(O)/rGO (x = 1.0, 1.5, 2.0) were constructed via proper calcination of pre-prepared hybrids CuxNi3-xAl-layered double hydroxide (LDH)/rGO in N2 flow, upon the LDH layer atomic-level lattice confine and dispersion effect on Cu2+ ions and in situ self-reduction by rGO substrate. The core@shell-like Cu@Cu2O NPs in composites are firmly trapped in the border space among vertically adjacent CuNiAl(O) nanosheets and rGO layers. The composites all show excellent catalytic activities for 4-NP reduction, especially 1.5Cu@Cu2O-CuNiAl(O)/rGO with the highest apparent rate constant of 7.6 × 10-2 s-1 and TOF of 265.0 h-1,along with insignificant loss in activity for continuous 25 cycles, much better than those of recently reported Cu-based catalysts and even comparable to some noble metal catalysts. The excellent performance can be mainly ascribed to uniformly dispersed electrophilic Cu@Cu2O NPs modified by NiO structurally and electronically, strong Cu−Cu2O−CuNiAl(O)−rGO synergy upon nanosheet array morphology, and improved adsorption for 4-NP by rGO due to π-π stacking. Moreover, the 1.5Cu@Cu2O-CuNiAl(O)/rGO shows excellent reduction and degradation performance for diverse nitroarenes and organic dyes. Further fixed bed tests reveal that 1.5Cu@Cu2O-CuNiAl(O)/rGO can be effectively used to catalytic degrade the mixture of 4-NP and methyl orange, implying practical application potential of the present hierarchical non-noble composites for water remediation.

Nanosheet array-like Cu@Cu2O-CuNiAl(O)/rGO composites promoted by NiO species: Superb catalytic efficiency and stability for nitrophenol reduction

ACS Fall 2021

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