Optimizing Intermediate Adsorption over PdM (M=Fe, Co, Ni, Cu) Bimetallene for Boosted Nitrate Electroreduction to Ammonia

Electrochemical reduction of nitrate to ammonia (NO3RR) is a promising and eco-friendly strategy for ammonia production. However, the sluggish kinetics of the eight-electron transfer process and poor mechanistic understanding strongly impedes its application. To unveil the internal laws, herein, a library of Pd-based bimetallene with various transition metal dopants (PdM (M=Fe, Co, Ni, Cu)) are screened to learn their structure-activity relationship towards NO3RR. The ultra-thin structure of metallene greatly facilitates the exposure of active sites, and the transition metals dopants break the electronic balance and upshift its d-band center, thus optimizing intermediates adsorption. The anisotropic electronic characteristics of these transition metals make the NO3RR activity in the order of PdCu>PdCo≈PdFe>PdNi>Pd, and a record-high NH3 yield rate of 295 mg h-1 mgcat -1 along with Faradaic efficiency of 90.9 % is achieved in neutral electrolyte on PdCu bimetallene. Detailed studies further reveal that the moderate N-species (*NO3 and *NO2) adsorption ability, enhanced *NO activation, and reduced HER activity facilitate the NH3 production. We believe our results will give a systematic guidance to the future design of NO3RR catalysts.

Evolution of Grain Boundaries Promoted Hydrogen Production for Industrial-Grade Current Density

The development of efficient and durable high-current-density hydrogen production electrocatalysts is crucial for the large-scale production of green hydrogen and the early realization of hydrogen economic blueprint. Herein, the evolution of grain boundaries through Cu-mediated NiMo bimetallic oxides (MCu-BNiMo), which leading to the high efficiency of electrocatalyst for hydrogen evolution process (HER) in industrial-grade current density, is successfully driven. The optimal MCu0.10-BNiMo demonstrates ultrahigh current density (>2 A cm-2) at a smaller overpotential in 1 m KOH (572 mV), than that of BNiMo, which does not have lattice strain. Experimental and theoretical calculations reveal that MCu0.10-BNiMo with optimal lattice strain generated more electrophilic Mo sites with partial oxidation owing to accelerated charge transfer from Cu to Mo, which lowers the energy barriers for H* adsorption. These synergistic effects lead to the enhanced HER performance of MCu0.10-BNiMo. More importantly, industrial application of MCu0.10-BNiMo operated in alkaline electrolytic cell is also determined, with its current density reached 0.5 A cm-2 at 2.12 V and 0.1 A cm-2 at 1.79 V, which is nearly five-fold that of the state-of-the-art HER electrocatalyst Pt/C. The strategy provides valuable insights for achieving industrial-scale hydrogen production through a highly efficient HER electrocatalyst.