A facile synthetic strategy for nitrogen-deficient graphitic carbon nitride (g-C N ) is established, involving a simple alkali-assisted thermal polymerization of urea, melamine, or thiourea. In situ introduced nitrogen vacancies significantly redshift the absorption edge of g-C N , with the defect concentration depending on the alkali to nitrogen precursor ratio. The g-C N products show superior visible-light photocatalytic performance compared to pristine g-C N .

Dinitrogen reduction to ammonia using transition metal catalysts is central to both the chemical industry and the Earth's nitrogen cycle. In the Haber–Bosch process, a metallic iron catalyst and high temperatures (400 °C) and pressures (200 atm) are necessary to activate and cleave NN bonds, motivating the search for alternative catalysts that can transform N2 to NH3 under far milder reaction conditions. Here, the successful hydrothermal synthesis of ultrathin TiO2 nanosheets with an abundance of oxygen vacancies and intrinsic compressive strain, achieved through a facile copper‐doping strategy, is reported. These defect‐rich ultrathin anatase nanosheets exhibit remarkable and stable performance for photocatalytic reduction of N2 to NH3 in water, exhibiting photoactivity up to 700 nm. The oxygen vacancies and strain effect allow strong chemisorption and activation of molecular N2 and water, resulting in unusually high rates of NH3 evolution under visible‐light irradiation. Therefore, this study offers a promising and sustainable route for the fixation of atmospheric N2 using solar energy.

Defect-rich ultrathin ZnAl-layered double hydroxide nanosheets are successfully prepared. Under UV-vis irradiation, these nanosheets are superior efficient catalysts for the photoreduction of CO2 to CO with water. The formed oxygen vacancies lead to the formation of coordinatively unsaturated Zn(+) centers within the nanosheets, responsible for the very high photocatalytic activities.

Nitrogen-doped porous carbon nanosheets (N-CNS) are synthesized by hydrothermal carbon coating of g-C3 N4 nanosheets followed by high-temperature treatment in N2 . g-C3 N4 serves as a template, nitrogen source, and porogen in the synthesis. This approach yields N-CNS with a high nitrogen content and comparable oxygen reduction reaction catalytic activities to commercial Pt/C catalysts in alkaline media.

Mo 2 C, [ 5 ] MoB, [ 5 a] NiMoN x , [ 6 ] and Co 0.6 Mo 1.4 N 2 , [ 7 ] whereas for OER-layered double hydroxides (LDHs) containing nickle, [ 8 ] cobalt, [ 8 b, 9 ] and iron [ 8 a, c, 10 ] or their calcination-derived mixed metal oxide (MMO) nanocomposites show good and stable activities. [ 11 ] However, the majority of these electrocatalysts are either semiconducting or insulating, which greatly hinders electron transfer from the electrocatalyst to the support electrode, thereby restricting their overall effi ciency and utilization potential. Using a single bifunctional OER and HER catalyst can simplify the water splitting system and also lowers the cost. [ 12 ] However, this is challenging since the same material must be able to effectively catalyze both the OER and HER while achieving a low overall overpotential and as high a current density as possible. [ 13 ] Compared to oxides and hydroxides of a particular metal, metal nitrides often display superior water-splitting activities owing to their special properties such as low electrical resistance and good corrosion resistance. [ 14 ] Recently, the synthesis of Ni 3 N nanosheets was reported for the fi rst time, [ 15 ] which potentially could represent a new class of OER electrocatalyst with better properties than NiO. Compared with single-metal nitrides, the activity of double metal nitrides can more readily be optimized through a controlled manipulation of the valence and electronic states of the metal elements, resulting in enhanced water-splitting performance. [ 7 ] LDHs are a family of layered clays containing divalent and trivalent metal cations, which can include electrochemically active elements such as Ni, Fe, and Co amongst others. [ 16 ] LDH nanosheets with ultrathin atomic scale thickness can readily be synthesized using top-down or bottom-up approaches. [ 17 ] Thermal ammonolysis of LDH nanosheets could potentially lead to the formation of novel nanostructured mixed metal nitrides (MMNs) for electrocatalytic applications, though very little work has been conducted in this area to date. The viability of this approach for the rational design of nanostructured MMNs from LDH precursors for overall water splitting is systematically explored herein.In this work, Ni 3 FeN nanoparticles (Ni 3 FeN-NPs) with a particle size of 100 nm and a thickness of ≈9 nm are successfully synthesized by thermal ammonolysis of ultrathin NiFe-LDH nanosheets prepared using a reverse microemulsion method ( Scheme 1 ). The Ni 3 FeN-NPs exhibited extraordinarily high activities for both HER and OER with low overpotentials of 158 and 280 mV at 10 mA cm −2 , respectively, and Tafel slopes of 42 and 46 mV dec −1 , respectively. The remarkable electrocatalytic activity of Ni 3 FeN-NPs can be attributed to highly exposed active sites and high electrical conductivity. This work conclusively Demand for clean renewable energy will increase enormously over the next 50-100 years, driven by rapid human population growth, fast depletion of fossil fuel resources, and environmental ...

Faceted NiO nanoparticles preferentially exposing high surface energy planes demand attention due to their excellent electrocatalytic properties. However, the activity of faceted NiO nanoparticles generally remains suboptimal due to their large lateral size and thickness, which severely limits the availability of coordinatively unsaturated active reactive edge and corner sites. Here, ultrafine NiO nanosheets with a platelet size of ∼4.0 nm and thickness (∼1.1 nm) stabilized by TiO2 were successfully prepared by calcination of a monolayer layered double hydroxide precursor. The ultrafine NiO nanosheets displayed outstanding performance in electrochemical water oxidation due to a high proportion of reactive NiO {110} facets, intrinsic Ni(3+) and Ti(3+) sites, and abundant interfaces, which act synergistically to promote H2O adsorption and facilitate charge-transfer.

Semiconductor photocatalysis attracts widespread interest in water splitting, CO reduction, and N fixation. N reduction to NH is essential to the chemical industry and to the Earth's nitrogen cycle. Industrially, NH is synthesized by the Haber-Bosch process under extreme conditions (400-500 °C, 200-250 bar), stimulating research into the development of sustainable technologies for NH production. Herein, this study demonstrates that ultrathin layered-double-hydroxide (LDH) photocatalysts, in particular CuCr-LDH nanosheets, possess remarkable photocatalytic activity for the photoreduction of N to NH in water at 25 °C under visible-light irradiation. The excellent activity can be attributed to the severely distorted structure and compressive strain in the LDH nanosheets, which significantly enhances N chemisorption and thereby promotes NH formation.

The enzyme nitrogenase inspires the development of novel photocatalytic and electrocatalytic systems that can drive nitrogen reduction with water under similar low‐temperature and low‐pressure conditions. While photocatalytic and electrocatalytic N 2 fixation are emerging as hot new areas of fundamental and applied research, serious concerns exist regarding the accuracy of current methods used for ammonia detection and quantification. In most studies, the ammonia yields are low and little consideration is given to the effect of interferants on NH 3 quantification. As a result, NH 3 yields reported in many works may be exaggerated and erroneous. Herein, the advantages and limitations of the various methods commonly used for NH 3 quantification in solution (Nessler's reagent method, indophenol blue method, and ion chromatography method) are systematically explored, placing particular emphasis on the effect of interferants on each quantification method. Based on the data presented, guidelines are suggested for responsible quantification of ammonia in photocatalysis and electrocatalysis.