Coordination and Architecture Regulation of Electrocatalysts for Sustainable Hydrogen Energy Conversion

With the increasing concerns about the energy and environmental crisis, hydrogen, with the high energy density and cleanliness, has been widely regarded as one ideal energy carrier for adjusting the fossil fuel dependent energy system. In this context, extensive studies are focused on improving the efficiency of the sustainable hydrogen production, storage, and utilization coupled with the renewable energy. And it can be realized in electrolysis cells and fuel cell devices. Several electrochemical reactions are involved, such as water splitting (hydrogen/oxygen evolution: HER/OER) for hydrogen production, electroreduction of nitrogen/nitrate, and carbon dioxide to NH3 and HCOOH (NRR, NO3RR, CO2RR) for hydrogen storage, and oxygen reduction reaction (ORR) for hydrogen utilization. However, the achieved efficiency of the hydrogen energy conversion is still unsatisfactory due to these intrinsically sluggish electrochemical reactions, which has spawned a revival of research interests in developing the electrocatalysts with high activity, selectivity, and durability. Therefore, various strategies have been established to construct effective electrocatalysts, such as coordination or architecture structure regulation, which will determine the intrinsic activity and the efficiency of mass transport, respectively. Besides, combined with the progress of characterization techniques and theoretical studies, insightful understanding of the electrocatalytic sites and reaction mechanism are also investigated, guiding the rational design of future electrocatalysts. In this Account, we summarize our recent efforts in exploring electrocatalysts through the regulation of coordination and construction of porous architecture structures toward the highly efficient electrochemical hydrogen energy conversion. First, an overview of the hydrogen energy conversion process is presented to reveal the advantages and challenges of these reactions. Then, we introduced effective strategies to optimize the coordination and architecture structure to enhance the catalytic performance, such as tailoring the particle size, valence state, and crystal plane, defect engineering, substrate incorporation, structural reconstruction, etc. Additionally, it is also illustrated the insightful mechanism study on the improvement of the catalytic performance via the experimental characterization and theoretical calculations. Finally, a brief outlook is proposed to address the challenges to be overcome for improving the hydrogen conversion efficiency through developing rational catalysts.