Construction of Ni-based N-doped mesoporous carbon sphere for efficiently catalytic dichromate reduction with HCOOH at room temperature

• Ni NPs@N-doped carbon spheres are prepared by pyrolyzing precursors with Ni salts and utilized as a catalyst for reducing Cr(VI). • Ni-N-C600 can completely reduce the high concentrations of Cr(VI) (100 mg/L, 100 ml) within 7 min. • Ni-N-C600 shows superior activity, selectivity, and stability for reducing Cr(VI). • The reduction mechanism includes active hydrogen and electronic donation of functional groups. The pollution of poisonous Cr(VI) poses a severe threat to our health, and the reduction of Cr(VI) to Cr(III) has become a high-efficiency way for wastewater remediation. Herein, the catalyst with metallic Ni confined in an N-doped mesoporous carbon sphere was prepared by the easy pyrolysis method of carbon sphere with Ni salts and showed remarkable activity, selectivity, and stability for reducing Cr(VI) with HCOOH. Notably, the Ni-N-C600 can rapid and 100 % reduction of the high concentrations of Cr(VI) (100 mg/L, 100 ml) using HCOOH within 7 min at room temperature over the reported Ni-based catalysts. Even in the presence of coexisting ions (0.1 M of Na + , K + , Ca 2+ , Zn 2+ , NO 3 − , Cl − , CO 3 2− , and SO 4 2− ), its catalytic efficiency is not affected at all. The catalytic activity of the Ni-N-C600 declined little even after five cycles because the confinement effect of the mesoporous carbon sphere physical barrier prevented the leaching and aggregation of Ni NPs. The magnetism of metallic Ni greatly facilitates the separation of the catalyst. The reduction mechanism is mainly achieved by active hydrogen produced through the dehydrogenation of HCOOH. In addition, the electronic donation of C-containing functional groups also caused a partial reduction of Cr(VI). This work provides a rational design and development of high-efficiency non-noble metal catalysts to reduce Cr(VI).