Innovative catalysts for the selective catalytic reduction of NOx with H2: A systematic review

Selective catalytic reduction (SCR) has been demonstrated to be an effective technique for reducing nitrogen oxides (NOx) emissions. Among various SCR technologies, selective catalytic reduction with hydrogen (H2-SCR) is recognized as an effective NOx removal technique due to its several advantages. These include high selectivity, lower temperature operation, compatibility with various catalysts, hydrogen availability, reduced dependency on noble metals, and environmental friendliness, making it a green technology choice for effective NOx reduction and sustainable emissions control. In recent years, H2-SCR has gained widespread recognition as a highly effective NOx reduction technology under lean-burn conditions. This review article provides an overview of the recent advancements in H2-SCR catalyst research, focusing on their novel features. Various possible mechanisms of the H2-SCR reaction, the influence of various preparation methods of catalysts, and the use of diverse supporting materials on the effectiveness of catalysts for NOx reduction are all covered in this review. This review examines the impact of diverse catalyst active components, supports, and promoters on the H2-SCR of NOx. Moreover, the review comprehensively examines discrete active components, including noble metal catalysts, non-noble metal catalysts, and bimetallic catalysts. The review also analyzes the homogeneous reactions of H2-SCR catalysts with exhaust gas components. From a practical viewpoint, the effects of exhaust gas composition on H2-SCR are discussed in detail. The article concludes by proposing potential opportunities and challenges in the field of H2-SCR, along with the corresponding effective strategies. By critically examining the most recent progress in innovative catalysts, this systematic review provides a comprehensive understanding of the current state of emissions control technology and significantly contributes to the advancement of innovations in the future.