Research Article Issue
Sequential reactant water management by complementary multisite catalysts for surpassing platinum hydrogen evolution activity
Nano Research 2024, 17 (3): 1232-1241
Published: 23 August 2023

Alkaline hydrogen evolution reaction (HER) offers a near-zero-emission approach to advance hydrogen energy. However, the activity limited by the multiple reaction steps involving H2O molecules transfer, absorption, and activation still unqualified the thresholds of economic viability. Herein, we proposed a multisite complementary strategy that incorporates hydrophilic Mo and electrophilic V into Ni-based catalysts to divide the distinct steps on atomically dispersive sites and thus realize sequential regulation of the HER process. The Isotopic labeled in situ Raman spectroscopy describes 4-coordinated hydrogen bonded H2O to be free H2O passing the inner Helmholtz plane in the vicinity of the catalysts under the action of hydrophilic Mo sites. Furthermore, potential-dependent electrochemical impedance spectroscopy (EIS) reveals that electrophilic V sites with abundant 3d empty orbitals could activate the lone-pair electrons in the free H2O molecules to produce more protic hydrogen, and dimerize into H2 at the Ni sites. By the sequential management of reactive H2O molecules, NiMoV oxides multisite catalysts surpass Pt/C hydrogen evolution activity (49 mV@10 mA∙cm−2 over 140 h). Profoundly, this study provides a tangible model to deepen the comprehension of the catalyst–electrolyte interface and create efficient catalysts for diverse reactions.

Research Article Issue
Nanopore-rich NiFe LDH targets the formation of the high-valent nickel for enhanced oxygen evolution reaction
Nano Research 2023, 16 (2): 2286-2293
Published: 15 December 2022

Nickel-iron layered double hydroxides (NiFe LDHs) represent a promising candidate for oxygen evolution reaction (OER), however, are still confronted with insufficient activity, due to the slow kinetics of electrooxidation of Ni2+ cations for the high-valent active sites. Herein, nanopore-rich NiFe LDH (PR-NiFe LDH) nanosheets were proposed for enhancing the OER activity together with stability. In the designed catalyst, the confined nanopores create abundant unsaturated Ni sites at edges, and decrease the migration distance of protons down to the scale of their mean free path, thus promoting the formation of high-valent Ni3+/4+ active sites. The unique configuration further improves the OER stability by releasing the lattice stress and accelerating the neutralization of the local acidity during the phase transformation. Thus, the optimized PR-NiFe LDH catalysts exhibit an ultralow overpotential of 278 mV at 10 mA∙cm−2 and a small Tafel slope of 75 mV∙dec−1, which are competitive among the advanced LDHs based catalysts. Moreover, the RP-NiFe LDH catalyst was implemented in anion exchange membrane (AEM) water electrolyzer devices and operated steadily at a high catalytic current of 2 A over 80 h. These results demonstrated that PR-NiFe LDH could be a viable candidate for the practical electrolyzer. This concept also provides valuable insights into the design of other catalysts for OER and beyond.

Review Article Issue
Chemical-vapor-deposition-grown 2D transition metal dichalcogenides: A generalist model for engineering electrocatalytic hydrogen evolution
Nano Research 2023, 16 (1): 101-116
Published: 19 August 2022

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have proved to possess exceptional catalytic performance for hydrogen evolution and are considered to be an appropriate substitute for commercial Pt-based catalysts. Experimentally, chemical vapor deposition (CVD) is an extremely important technique for acquiring controllable and high-purity TMDs for electrocatalysis and modern electronic devices. Recently, researchers have made significant achievements in synthesizing TMDs used for electrocatalytic hydrogen evolution by CVD ranging from dynamic mechanism exploration to performance optimization. In this review, we present the recent progress based on electrocatalytic hydrogen evolution implemented by CVD-growth TMDs nanosheets and unveil the structural–activity correlation. Firstly, in synthesis, diverse factors covering precursor, substrate, temperature settings, and atmosphere will affect the quality and surface morphology of TMDs. Then, we present the current research status of the CVD-grown 2D TMDs for engineering electrocatalytic hydrogen evolution, including intrinsic performance exploring, morphology engineering, composition adjusting, phase engineering, and vertically-oriented structure constructing. Finally, the future prospects and challenges of CVD in 2D TMDs electrocatalysis are provided.

Research Article Issue
Multi-scale regulation in S, N co-incorporated carbon encapsulated Fe-doped Co9S8 achieving efficient water oxidation with low overpotential
Nano Research 2022, 15 (2): 872-880
Published: 16 June 2021

Sulfide compounds provide a type of promising alternative for oxygen evolution reaction (OER) electrocatalysts due to their diversity, intrinsic activities, low-price and earth-abundance. However, the unsmooth mass transport channel, the collapse of the structure and insufficient intrinsic activities limit their potential for OER performance. In respond, the dense Fe-doped Co9S8 nanoparticles encapsulated by S, N co-incorporated carbon nanosheets (Fe-Co9S8@SNC) were proposed and synthesized via fast thermal treatment from ultrathin metal-organic frameworks (MOFs) nanosheets. In designed catalysts, the nanosheet configuration connected by nanoparticles retained rich access for permeation of electrolyte and precipitation of O2 bubbles during OER process. Meanwhile, the outer carbon layer of Co9S8 provided additional catalytic activity while acting as armor to keep the structure stability. At the atomic scale, the doped Fe regulated the local charge density and the d-band center for facilitating desorption of oxygen intermediates. Benefiting from this multi-scale regulation strategy, the Fe-Co9S8@SNC displays an ultralow overpotential of 273 mV at 10 mA·cm-2 and small Tafel slope of 55.8 mV·dec-1, which is even close to the benchmark RuO2 catalyst. This concept could provide valuable insights into the design of other catalysts for OER and beyond.

Research Article Issue
Single MoTe2 sheet electrocatalytic microdevice for in situ revealing the activated basal plane sites by vacancies engineering
Nano Research 2021, 14 (12): 4814-4821
Published: 24 April 2021

Activating basal plane inert sites will endow MoTe2 with prominent hydrogen evolution reaction (HER) catalytic capability and arouse a new family of HER catalysts. Herein, we fabricated single MoTe2 sheet electrocatalytic microdevice for in situ revealing the activated basal plane sites by vacancies introducing. Through the extraction of electrical parameters of single MoTe2 sheet, the in-plane and interlayer conductivities were optimized effectively by Te vacancies due to the defect levels. More deeply, Te vacancies can induce the delocalization of electrons around Mo atoms and shift the d-band center, as a consequence, facilitate the adsorption of H from the catalyst surface for HER catalysis. Benefiting by the coordinated regulation of band structure and local charge density, the overpotential at –10 mA∙cm−2 was reduced to 0.32 V after Te vacancies compared to 0.41 V for the basal plane sites of same MoTe2 nanosheet. Meanwhile, the insights gained from single nanosheet electrocatalytic microdevice can be applied to the improved HER of the commercial MoTe2 power. That the in situ testing of the atomic structure-electrical behavior-electrochemical properties of a single nanosheet before/after vacancies introducing provides reliable insight to structure-activity relationships.

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