A hydrogen-centric perspective on electrocatalytic nitrate reduction: Managing the active hydrogen lifecycle from generation to utilization

Abstract

Electrocatalytic nitrate reduction reaction (NitRR) utilizing water as a hydrogen source under ambient conditions represents a highly promising avenue for sustainable ammonia synthesis and environmental remediation. However, achieving high efficiency and selectivity in NitRR is fundamentally challenged by the complex lifecycle management of active hydrogen derived from water splitting. This review provides a timely and comprehensive analysis centered on the pivotal role and meticulous regulation of active hydrogen throughout the NitRR process. We first elucidate the distinct functions and characteristics of various hydrogen species, followed by a survey of advanced characterization techniques crucial for monitoring the dynamics of active hydrogen. Critically, three core strategies were systematically dissected to modulate the active hydrogen lifecycle: accelerating water activation and dissociation, enhancing the directional transport of hydrogen species, and precisely tuning active hydrogen coupling pathways while suppressing parasitic hydrogen evolution. By consolidating current understanding from both catalyst design and reaction mechanism perspectives, this review offers a hydrogen-centric roadmap and highlights emerging opportunities for rationally engineering advanced NitRR systems.