Excessive discharge of nitrate pollutants has caused an imbalance in the nitrogen cycle, which has threatened human health and ecosystems. Clean electrocatalytic nitrate reduction technology can convert nitrate into high value-added ammonia to control water pollution, truly realizing “turning waste into treasure”. This review highlights the latest mechanisms proposed by combining in situ characterization and discusses the various intermediates produced during the reaction process and the key steps that determine the reaction rate. Meanwhile, four common catalyst synthesis strategies are systematically summarized. These strategies have exhibited preeminent results in terms of conductivity and active sites and inhibition of side effects. Finally, the challenges and difficulty of electrocatalytic nitrate reduction into ammonia (NRA) in the process of development and the main development direction in the future are discussed. The engineering strategies for increasing the electrocatalytic stability and performance are also discussed. This review aims to provide guidance for efficient electrocatalytic nitrate conversion and promotes the advancement of sustainable nitrogen chemistry.

Defect engineering is one of the effective strategies to regulate and control catalyst properties. Constructing appropriate catalytic active centers effectively tunes the electronic andsurface properties of the catalyst to achieve...

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Failure of brittle rock normally initiates from tensile fracture due to its extraordinary lower resistance to tension rather than to compression. Intensive study on the deformability and accurate acquirement of the mechanical properties of rock under tensile stress is crucial for the stability analysis of rock slope and rock caverns. A new set of centering apparatuses, which consist of the specimen bonding part and the axial pulling part, were developed in this study. The misalignments when bonding the specimen and conducting the uniaxial tensile test can be effectively eliminated. Direct tensile tests were conducted on various brittle rocks cored from several large-scale hydropower station sites in China. The tensile strength, tensile elastic modulus, maximum tensile strain, and complete stress-strain curves were successfully obtained. The direct tensile test results indicated that the fracture surface formed in the central part of the specimen, which was under uniform tensile stress. The fracture surfaces were mostly perpendicular to the specimen axis. Fresh fractures without accumulation of rock fragments can be observed and characterized as tensile brittle failure. The microscopic failure modes of brittle rocks under the direct tensile test were not unique but consisted of the intragranular and intergranular fractures. The direct tensile strength (DTS) was generally lower than the Brazilian tensile strength (BTS) (DTS/BTS = 0.60~0.71). The direct tensile test was therefore recommended for the measurement of the tensile mechanical properties in order to ensure the safety of rock engineering.

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