Developing active single-atom-catalyst (SAC) for alkaline hydrogen evolution reaction (HER) is a promising solution to lower the green hydrogen cost. However, the correlations are not clear between the chemical environments around the active-sites and their desired catalytic activity. Here we study a group of SACs prepared by anchoring platinum atoms on NiFe-layered-double-hydroxide. While maintaining the homogeneity of the Pt-SACs, various axial ligands (−F, −Cl, −Br, −I, −OH) are employed via a facile irradiation-impregnation procedure, enabling us to discover definite chemical-environments/performance correlations. Owing to its high first-electron-affinity, chloride chelated Pt-SAC exhibits optimized bindings with hydrogen and hydroxide, which favor the sluggish water dissociation and further promote the alkaline HER. Specifically, it shows high mass-activity of 30.6 A mgPt−1 and turnover frequency of 30.3  H2 s−1 at 100 mV overpotential, which are significantly higher than those of the state-of-the-art Pt-SACs and commercial Pt/C catalyst. Moreover, high energy efficiency of 80% is obtained for the alkaline water electrolyser assembled using the above catalyst under practical-relevant conditions.

Single‐atom catalysts (SACs) with rationally designed microenvironments (defined as coordination environments and electronic configurations) show superior catalytic activity, selectivity, and stability in a majority of reactions. However, the construction of isolated SACs with definite microenvironments to understand the microenvironment–activity relationship is still challenging. Herein, a facile strategy is developed to construct a series of Ru SACs with tunable geometric and electronic structures by employing NiFe‐layered double hydroxides (LDH) with different cation vacancies (MII or MIII) as supports. Detailed spectroscopic characterizations and theoretical calculations reveal that the Ru‐O coordination environments and electronic configurations of single‐atomic Ru can be easily tailored by the vacancy regulation. As a result, isolated Ru atoms anchored by MIII vacancies (denoted as Ru1/LDH‐VIII) with Ru‐O‐Ni coordination environments facilitate the desorption of benzaldehyde, thus leading to higher efficiency of benzyl alcohol oxidation with a superior turnover frequency of 1331 h−1.

No abstract

Developing efficient nanozymes to mimic natural enzymes for scavenging reactive radicals remains a significant challenge owing to the insufficient activity of conventional nanozymes. Herein, we report a novel Ru single‐atom nanozyme (SAE), featuring atomically dispersed Ru atoms on a biocompatible MgAl‐layered double hydroxide (Ru1/LDH). The prepared Ru1/LDH SAE shows high intrinsic peroxidase (POD)‐like catalytic activity, which outperforms the Ru nanoclusters (NCs) nanozyme by a factor of 20 and surpasses most SAEs. The density functional theory calculations reveal that the high intrinsic POD‐like activity of Ru1/LDH can be attributed to a heterolytic path of H2O2 dissociation on the single Ru sites, which requires lower free energy (0.43 eV) compared to the homolytic path dissociation on Ru NC (0.63 eV). In addition, the Ru1/LDH SAE shows excellent multiple free radicals scavenging ability, including superoxide anion radical (O2⋅−), hydroxyl radical (⋅OH), nitric oxide radical (NO⋅) and 2, 2‐diphenyl‐1‐picrylhydrazyl radical (DPPH⋅). Given the advantages of Ru1/LDH with high enzymatic activities, biosafety, and ease to scale up, it paves the way for exploring SAEs in the practical biological immunity system.

Developing efficient nanozymes to mimic natural enzymes for scavenging reactive radicals remains a significant challenge owing to the insufficient activity of conventional nanozymes. Herein, we report a novel Ru single‐atom nanozyme (SAE), featuring atomically dispersed Ru atoms on a biocompatible MgAl‐layered double hydroxide (Ru1/LDH). The prepared Ru1/LDH SAE shows high intrinsic peroxidase (POD)‐like catalytic activity, which outperforms the Ru nanoclusters (NCs) nanozyme by a factor of 20 and surpasses most SAEs. The density functional theory calculations reveal that the high intrinsic POD‐like activity of Ru1/LDH can be attributed to a heterolytic path of H2O2 dissociation on the single Ru sites, which requires lower free energy (0.43 eV) compared to the homolytic path dissociation on Ru NC (0.63 eV). In addition, the Ru1/LDH SAE shows excellent multiple free radicals scavenging ability, including superoxide anion radical (O2⋅−), hydroxyl radical (⋅OH), nitric oxide radical (NO⋅) and 2, 2‐diphenyl‐1‐picrylhydrazyl radical (DPPH⋅). Given the advantages of Ru1/LDH with high enzymatic activities, biosafety, and ease to scale up, it paves the way for exploring SAEs in the practical biological immunity system.