No abstract

Achieving active and stable oxygen evolution reaction (OER) in acid media based on single-atom catalysts is highly promising for cost-effective and sustainable energy supply in proton electrolyte membrane electrolyzers. Here, we report an atomically dispersed Ru1-N4 site anchored on nitrogen-carbon support (Ru-N-C) as an efficient and durable electrocatalyst for acidic OER. The single-atom Ru-N-C catalyst delivers an exceptionally intrinsic activity, reaching a mass activity as high as 3571 A gmetal−1 and turnover frequency of 3348 O2 h−1 with a low overpotential of 267 mV at a current density of 10 mA cm−2. The catalyst shows no evident deactivation or decomposition after 30-hour operation in acidic environment. Operando synchrotron radiation X-ray absorption spectroscopy and infrared spectroscopy identify the dynamic adsorption of single oxygen atom on Ru site under working potentials, and theoretical calculations demonstrate that the O-Ru1-N4 site is responsible for the high OER activity and stability.

An active and stable photocatalyst to directly split water is desirable for solar-energy conversion. However, it is difficult to accomplish overall water splitting without sacrificial electron donors. Herein, we demonstrate a strategy via constructing a single site to simultaneously promote charge separation and catalytic activity for robust overall water splitting. A single Co -P site confined on g-C N nanosheets was prepared by a facile phosphidation method, and identified by electron microscopy and X-ray absorption spectroscopy. This coordinatively unsaturated Co site can effectively suppress charge recombination and prolong carrier lifetime by about 20 times relative to pristine g-C N , and boost water molecular adsorption and activation for oxygen evolution. This single-site photocatalyst exhibits steady and high water splitting activity with H evolution rate up to 410.3 μmol h g , and quantum efficiency as high as 2.2 % at 500 nm.

Knowledge of the photocatalytic H evolution mechanism is of great importance for designing active catalysts toward a sustainable energy supply. An atomic-level insight, design, and fabrication of single-site Co -N composite as a prototypical photocatalyst for efficient H production is reported. Correlated atomic characterizations verify that atomically dispersed Co atoms are successfully grafted by covalently forming a Co -N structure on g-C N nanosheets by atomic layer deposition. Different from the conventional homolytic or heterolytic pathway, theoretical investigations reveal that the coordinated donor nitrogen increases the electron density and lowers the formation barrier of key Co hydride intermediate, thereby accelerating H-H coupling to facilitate H generation. As a result, the composite photocatalyst exhibits a robust H production activity up to 10.8 μmol h , 11 times higher than that of pristine counterpart.

The development of atomically precise dinuclear heterogeneous catalysts is promising to achieve efficient catalytic performance and is also helpful to the atomic-level understanding on the synergy mechanism under reaction conditions. Here, we report a Ni 2 (dppm) 2 Cl 3 dinuclear-cluster-derived strategy to a uniform atomically precise Ni 2 site, consisting of two Ni 1 −N 4 moieties shared with two nitrogen atoms, anchored on a N-doped carbon. By using operando synchrotron X-ray absorption spectroscopy, we identify the dynamically catalytic dinuclear Ni 2 structure under electrochemical CO 2 reduction reaction, revealing an oxygen-bridge adsorption on the Ni 2 −N 6 site to form an O−Ni 2 −N 6 structure with enhanced Ni−Ni interaction. Theoretical simulations demonstrate that the key O−Ni 2 −N 6 structure can significantly lower the energy barrier for CO 2 activation. As a result, the dinuclear Ni 2 catalyst exhibits >94% Faradaic efficiency for efficient carbon monoxide production. This work provides bottom-up target synthesis approaches and evidences the identity of dinuclear sites active toward catalytic reactions.

An active and stable photocatalyst to directly split water is desirable for solar‐energy conversion. However, it is difficult to accomplish overall water splitting without sacrificial electron donors. Herein, we demonstrate a strategy via constructing a single site to simultaneously promote charge separation and catalytic activity for robust overall water splitting. A single Co1‐P4 site confined on g‐C3N4 nanosheets was prepared by a facile phosphidation method, and identified by electron microscopy and X‐ray absorption spectroscopy. This coordinatively unsaturated Co site can effectively suppress charge recombination and prolong carrier lifetime by about 20 times relative to pristine g‐C3N4, and boost water molecular adsorption and activation for oxygen evolution. This single‐site photocatalyst exhibits steady and high water splitting activity with H2 evolution rate up to 410.3 μmol h−1 g−1, and quantum efficiency as high as 2.2 % at 500 nm.

Modulating the electronic structure of cocatalysts is critical for designing active sites toward efficient photocatalytic H 2 evolution. Here, we report an electronic modulation in atomically dispersed Pt as highly efficient H 2 -evolution sites on graphitic carbon nitride (g-C 3 N 4 ) nanosheets. Synchrotron radiation X-ray spectroscopic results confirm the singly dispersed Pt atoms anchored on g-C 3 N 4 via forming "Pt 1 −N 4 " moiety, where the strong interaction of Pt with supports leads to the redistribution of Pt valence electrons with the highly vacant 5d orbital. Mechanistic investigations reveal that the immobilization of Pt single atoms with electron-deficient 5d orbitals on g-C 3 N 4 nanosheets not only facilitate the separation of electron−holes pair but also optimize the water reduction kinetics on the surface. As a result, the Pt single atoms photocatalyst achieves a high intrinsic activity with turnover frequency of 250 h −1 , about 13 times higher than the 19.5 h −1 of its nanocrystal counterpart.

Electrochemical water splitting in alkaline media is an attractive way to produce the clear and renewable hydrogen fuel H 2 . In this work, we report a single-atom Fe 1 /NC catalyst, where the Fe−N x moiety works as the active site, for high-efficiency alkaline hydrogen evolution reaction (HER). The Fe 1 /NC electrocatalyst exhibits a low overpotential of 111 mV at the current density of 10 mA cm −2 , with a Tafel slope of 86.1 mV dec −1 in 1 M KOH solution. Operando X-ray absorption spectroscopy reveals that, under the working states, the Fe− support interaction weakened as the Fe−N coordination number and Fe oxidation state decreased. As such, the evolved single-atom Fe site with more d electrons provides a favorable structure for boosting HER performance. This work gives insight into the structural evolution of the active site under the alkaline HER and provides a strategy for the design of non-noble metal electrocatalysts.