Unearthing an ideal model for disclosing the role of defect sites in solar CO reduction remains a great challenge. Here, freestanding gram-scale single-unit-cell o-BiVO layers are successfully synthesized for the first time. Positron annihilation spectrometry and X-ray fluorescence unveil their distinct vanadium vacancy concentrations. Density functional calculations reveal that the introduction of vanadium vacancies brings a new defect level and higher hole concentration near Fermi level, resulting in increased photoabsorption and superior electronic conductivity. The higher surface photovoltage intensity of single-unit-cell o-BiVO layers with rich vanadium vacancies ensures their higher carriers separation efficiency, further confirmed by the increased carriers lifetime from 74.5 to 143.6 ns revealed by time-resolved fluorescence emission decay spectra. As a result, single-unit-cell o-BiVO layers with rich vanadium vacancies exhibit a high methanol formation rate up to 398.3 μmol g h and an apparent quantum efficiency of 5.96% at 350 nm, much larger than that of single-unit-cell o-BiVO layers with poor vanadium vacancies, and also the former's catalytic activity proceeds without deactivation even after 96 h. This highly efficient and spectrally stable CO photoconversion performances hold great promise for practical implementation of solar fuel production.

Nitrate is ar aw ingredient for the production of fertilizer,g unpowder,a nd explosives.D eveloping an alternative approach to activate the NNbond of naturally abundant nitrogen to form nitrate under ambient conditions will be of importance.Herein, pothole-rich WO 3 was used to catalyse the activation of N Nc ovalent triple bonds for the direct nitrate synthesis at room temperature.T he pothole-rich structure endues the WO 3 nanosheet more dangling bonds and more easily excited high momentum electrons,w hicho vercome the two major bottlenecks in NNb ond activation, that is,p oor binding of N 2 to catalytic materials and the high energy involved in this reaction. The average rate of nitrate production is as high as 1.92 mg g À1 h À1 under ambient conditions,without any sacrificial agent or precious-metal co-catalysts.M ore generally,t he concepts will initiate an ew pathwayf or triggering inert catalytic reactions.

Crystalline SnSe has been revealed as an efficient thermoelectric candidate with outstanding performance. Herein, record-high thermoelectric performance is achieved among SnSe crystals via simply introducing a small amount of SnSe 2 as a kind of extrinsic defect dopant. This excellent performance mainly arises from the largely enhanced power factor by increasing the carrier concentration high as 6.55 × 10 19 cm −3 , which was surprisingly promoted by introducing extrinsic SnSe 2 even though pristine SnSe 2 is an n-type conductor. The optimized carrier concentration promotes a deeper Fermi level and activates more valence bands, leading to an extraordinary room-temperature power factor ∼54 μW cm −1 K −2 through enlarging the band effective mass and Seebeck coefficient. As a result, on the basis of simultaneously depressed thermal conductivity induced from both Sn vacancies and SnSe 2 microdomains, maximum ZT values ∼0.9−2.2 and excellent average ZT > 1.7 among the working temperature range are achieved in Na doped SnSe crystals with 2% extrinsic SnSe 2 . Our investigation illustrates new approaches on improving thermoelectric performance through introducing defect dopants, which might be well-implemented in other thermoelectric systems.