Electrochemically converting nitrate, a widespread water pollutant, back to valuable ammonia is a green and delocalized route for ammonia synthesis, and can be an appealing and supplementary alternative to the Haber-Bosch process. However, as there are other nitrate reduction pathways present, selectively guiding the reaction pathway towards ammonia is currently challenged by the lack of efficient catalysts. Here we report a selective and active nitrate reduction to ammonia on Fe single atom catalyst, with a maximal ammonia Faradaic efficiency of ~ 75% and a yield rate of up to ~ 20,000 μg h−1 mgcat.−1 (0.46 mmol h−1 cm−2). Our Fe single atom catalyst can effectively prevent the N-N coupling step required for N2 due to the lack of neighboring metal sites, promoting ammonia product selectivity. Density functional theory calculations reveal the reaction mechanisms and the potential limiting steps for nitrate reduction on atomically dispersed Fe sites.

As the most well-known electrocatalyst for cathodic hydrogen evolution in water splitting electrolyzers, platinum is unfortunately inefficient for anodic oxygen evolution due to its over-binding with oxygen species and excessive dissolution in oxidative environment. Herein we show that single Pt atoms dispersed in cobalt hydrogen phosphate with an unique Pt(OH)(O3)/Co(P) coordination can achieve remarkable catalytic activity and stability for oxygen evolution. The catalyst yields a high turnover frequency (35.1 ± 5.2 s−1) and mass activity (69.5 ± 10.3 A mg−1) at an overpotential of 300 mV and excellent stability. Mechanistic studies elucidate that the superior catalytic performance of isolated Pt atoms herein stems from optimal binding energies of oxygen intermediate and also their strong electronic coupling with neighboring Co atoms that suppresses the formation of soluble Ptx>4 species. Alkaline water electrolyzers assembled with an ultralow Pt loading realizes an industrial-level current density of 1 A cm−2 at 1.8 volts with a high durability.

Aqueous zinc-ion batteries (AZIBs) are attractive energy storage devices that benefit from improved safety and negligible environmental impact. The V2O5-based cathodes are highly promising, but the dissolution of vanadium is one of the major challenges in realizing their stable performance in AZIBs. Herein, we design a Ti3C2T x MXene layer on the surface of V2O5 nanoplates (VPMX) through a van der Waals self-assembly approach for suppressing vanadium dissolution during an electrochemical process for greatly boosting the zinc-ion storage performance. Unlike conventional V2O5/C composites, we demonstrate that the VPMX hybrids offer three distinguishable features for achieving high-performance AZIBs: (i) the MXene layer on cathode surface maintains structural integrity and suppresses V dissolution; (ii) the heterointerface between V2O5 and MXene enables improved host electrochemical kinetics; (iii) reduced electrostatic repulsion exists among host layers owing to the lubricating water molecules in the VPMX cathode, facilitating interfacial Zn2+ diffusion. As a result, the as-made VPMX cathode shows a long-term cycling stability over 5000 cycles, surpassing other reported V2O5-based materials. Especially, we find that the heterointerface between V2O5 and MXene and lubricated water molecules in the host can achieve an enhanced rate capability (243.6 mAh g–1 at 5.0 A g–1) for AZIBs.

Designing efficient and durable bifunctional catalysts for 5-hydroxymethylfurfural (HMF) oxidation reaction (HMFOR) and hydrogen evolution reaction (HER) is desirable for the co-production of biomass-upgraded chemicals and sustainable hydrogen, which is limited by the competitive adsorption of hydroxyl species (OHads) and HMF molecules. Here, we report a class of Rh–O5/Ni­(Fe) atomic site on nanoporous mesh-type layered double hydroxides with atomic-scale cooperative adsorption centers for highly active and stable alkaline HMFOR and HER catalysis. A low cell voltage of 1.48 V is required to achieve 100 mA cm–2 in an integrated electrolysis system along with excellent stability (>100 h). Operando infrared and X-ray absorption spectroscopic probes unveil that HMF molecules are selectively adsorbed and activated over the single-atom Rh sites and oxidized by in situ-formed electrophilic OHads species on neighboring Ni sites. Theoretical studies further demonstrate that the strong d–d orbital coupling interactions between atomic-level Rh and surrounding Ni atoms in the special Rh–O5/Ni­(Fe) structure can greatly facilitate surface electronic exchange-and-transfer capabilities with the adsorbates (OHads and HMF molecules) and intermediates for efficient HMFOR and HER. We also reveal that the Fe sites in Rh–O5/Ni­(Fe) structure can promote the electrocatalytic stability of the catalyst. Our findings provide new insights into catalyst design for complex reactions involving competitive adsorptions of multiple intermediates.

The electrosynthesis of organic amines to high-value-added nitriles coupled with hydrogen generation is a highly efficient way to achieve carbon neutrality; however, the development of this method is greatly plagued by the lack of high-efficiency catalysts and an insufficient mechanistic understanding of electrochemical amine oxidation. Herein, a class of anion-vacancy and cation-substitution proof-of-concept atomically thin CoSe2 subnanometer belts (SBs) are reported to greatly boost the electrooxidation of butylamine into high-value-added butyronitrile coupled with hydrogen generation. The as-fabricated CoSe2 SBs with Se vacancies and Ni substitutions (CoSe2/Ni–SVs SBs) exhibit an ultralow onset potential of 1.3 V with up to a ∼98.5% butyronitrile Faradaic efficiency, which surpasses all the reported Co- and Ni-based catalysts. In situ electrochemical FTIR and EIS spectroscopy studies indicate that the dramatically enhanced electrooxidation performance can be attributed to the optimized adsorption behavior and accelerated dehydrogenation kinetics. Theoretical studies further reveal that Se vacancies can act as strong Lewis acid sites to effectively strengthen the adsorption of N atoms, whereas Ni substitutions are responsible for improving the dehydrogenation thermodynamics by optimizing the sequence of dehydrogenation steps. We further demonstrate that the CoSe2/Ni–SVs SBs are highly general and efficient catalysts for the electrosynthesis of propylamine, benzylamine, and cyclohexane methylamine into nitriles coupled with hydrogen generation. More importantly, a CoSe2/Ni–SVs SB-based two-electrode electrolyzer that uses amine oxidation at the anode can achieve a voltage of 1.37 V at a current density of 10 mA cm–2, which can lower the cell voltage by even 320 mV compared to that of a conventional two-electrode electrolyzer that uses the oxygen evolution reaction at the anode.