▎ 摘　　要

Direct photoconversion of diluted CO2 into solar fuels has theoretically and practically become a hot research topic. However, the low yields and poor selectivity of carbonaceous products hampered by the H-2 evolution reaction is still a challenge for its practical application. Herein, we demonstrate a three-dimensional (3D) nickel borate/graphene nanoarrays (Ni-B-i/G) for diluted CO2 photoreduction with boosted activity and selectivity. In simulated flue gas with 10% CO2, the pristine Ni-B-i displays a low activity and low CO selectivity of 41.8%, indicating its tendency of producing H-2 in diluted CO2. However, after growing Ni-B-i nanoarrays onto graphene nanosheets, the optimized 3D Ni-B-i/G exhibits a high CO selectivity of 84.9% with a CO production rate of 5.1 mu mol h(-1), which is about 2 times of the blank sample. The improved performance can be attributed to the synergistic effect of the introduction of rGO and unique 3D structure, which are conducive not only to accelerate the separation of photogenerated charges, but also to enrich active sites and enhance CO2 adsorption. This work provides fundamental guidance to the rational design of well-designed hierarchical catalysts for photoconversion of low concentration CO2.