The ammonia synthesis from nitrogen and water under ambient conditions is one of the most inviting but challenging reaction routes. Although nitrogen is abundant in the atmosphere and the ammonia synthesis reaction is exothermic on the thermodynamics, the conversion of N₂ to ammonia is actually hard to proceed owing to the chemical inertness and stability of N₂ molecules. In industry, ammonia synthesis is carried out by the Haber-Bosch process under harsh conditions (300–500 °C, 20–30 MPa) associated with the requirement of substantial energy input and the enormous emission of greenhouse gases (e.g., CO₂). Recently, a growing number of studies on photo(electro)catalytic and electrocatalytic nitrogen reduction reaction (NRR) in aqueous solution have attracted extensive attention, which holds great promise for nitrogen fixation under room temperature and atmospheric pressure. However, the very low efficiency and ambiguous mechanism still remain as the major hurdles for the development of photochemical and electrochemical NRR systems. Here we provide an overview of the latest progresses, remaining challenges and future prospects in photocatalytic and electrocatalytic nitrogen fixation. Moreover, this review offers a helpful guidance for the reasonable design of photocatalysts and electrocatalysts towards NRR by combining theory predictions and experiment results. We hope this review can stimulate more research interests in the relatively understudied but highly promising research field of NRR.

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在环境条件下由氮气和水合成氨是最诱人但最具挑战性的反应路线之一。尽管大气中氮丰富并且氨合成反应在热力学上是放热的，但是由于N ₂分子的化学惰性和稳定性，实际上难以将N ₂转化为氨。在工业中，氨的合成是通过Haber-Bosch工艺在苛刻的条件下（300–500°C，20–30 MPa）进行的，这需要大量的能量输入和大量的温室气体排放（例如CO _2））。近年来，越来越多的水溶液中光（电）催化和电催化氮还原反应（NRR）的研究引起了广泛的关注，这为在室温和大气压下固氮提供了广阔的前景。然而，非常低的效率和模糊的机理仍然是光化学和电化学NRR系统发展的主要障碍。在这里，我们概述了光催化和电催化固氮技术的最新进展，仍然存在的挑战和未来前景。此外，本综述结合理论预测和实验结果，为光催化剂和电催化剂向NRR的合理设计提供了有益的指导。

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