Nanosheet array-like Cu@Cu2O-CuNiAl(O)/rGO composites for highly efficient reduction of nitrophenol: Electronic and structure promotion effect of nickel

• LDH layer atomic-level lattice confined in situ self-reduction for Cu 2+ ions in LDH/rGO by rGO. • Nanosheet array composites Cu@Cu 2 O-CuNiAl(O)/rGO with high surface area and mesopores. • Highly active core@shell-type Cu@Cu 2 O nanoparticles with electrophilic surface. • Electronic and structure promotion effect of NiO phase on reduction of nitrophenols. • The strong Cu–Cu 2 O–CuNiAl(O)–rGO synergistic effect. Series of hierarchical nanosheet array-like composites x Cu@Cu 2 O-CuNiAl(O)/rGO ( x = 1.0, 1.5, 2.0) were constructed via proper calcination of pre-prepared hybrids Cu x Ni 3- x Al-layered double hydroxide/rGO in N 2 flow, upon the LDH layer atomic-level lattice confined in situ self-reduction for Cu 2+ ions by rGO substrate along with the dispersion effect of Ni-OH groups. Systematic characterizations reveal that core@shell-type Cu@Cu 2 O nanoparticles (NPs) are definitely trapped in the border space among the vertically adjacent CuNiAl(O) nanosheets and rGO substrates. All the x Cu@Cu 2 O-CuNiAl(O)/rGO composites exhibit excellent catalytic activities for the reduction of 4-nitrophenol (4-NP), particularly 1.5Cu@Cu 2 O-CuNiAl(O)/rGO possesses the highest activity (k app : 7.6 × 10 -2 s −1 , TOF: 265.0 h −1 ), and superb reusability 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 best performance of 1.5Cu@Cu 2 O-CuNiAl(O)/rGO can be mainly attributed to the most uniformly dispersed electrophilic core@shell Cu@Cu 2 O NPs modified by NiO species structurally and electronically, the strongest Cu–Cu 2 O–CuNiAl(O)–rGO synergistic effect upon the unique nanosheet array-like morphology providing more ion-accessible active sites, and much improved adsorption for 4-NP via rGO layer due to π-π stacking. The universality and fixed bed tests further demonstrate potential practical applications of the present hierarchical non-noble composites for water remediation. The present facile synthesis strategy of the nanosheet array-like Cu@Cu 2 O-CuNiAl(O)/rGO composites with multi-phases synergy may be greatly beneficial to the design and construction of many other highly efficient multi-transition metal-based catalysts with excellent structural robustness for a broad range of applications in related catalysis processes.