Research Article Online first
Ultra-stable Pt5La intermetallic compound towards highly efficient oxygen reduction reaction
Nano Research
Published: 22 September 2022

Designing feasible electrocatalysts towards oxygen reduction reaction (ORR) requires advancement in both activity and stability, where attaining high stability is of extreme importance as the catalysts are expected to work efficiently under frequent start-up/shut down circumstances for at least several thousand hours. Alloying platinum with early transition metals (i.e., Pt–La alloy) is revealed as efficient catalysts construction strategy to potentially satisfy these demands. Here we report a Pt5La intermetallic compound synthesized by a novel and facile strategy. Due to the strong electronic interactions between Pt and La, the resultant Pt5La alloy catalyst exhibits enhanced activity with half wave of 0.92 V and mass activity of 0.49 A·mgPt−1, which strictly follows the 4e transfer pathway. More importantly, the catalyst performs superior stability during 30,000 cycles of accelerated stressed test (AST) with mass activity retention of 93.9%. This study provides new opportunities for future applications of Pt-rare earth metal alloy with excellent electrocatalytic properties.

Research Article Online first
Identification of active sites and synergistic effect in multicomponent carbon-based Ru catalysts during electrocatalytic hydrogen evolution
Nano Research
Published: 05 August 2022

Single atom catalysts (SACs) were reported to demonstrate exciting catalytic features for a number of reactions, including hydrogen evolution reaction (HER). However, the true role of these single atom sites in catalysts remains elusive, particularly for those prepared via pyrolysis, where the formation of active nanoparticle counterparts is often unavoidable. Here we report a Ru based catalyst (Ru embedded in N doped carbon spheres (Ru/NPCS)) comprising of both Ru nanoclusters and Ru single sites, who demonstrates activity exceeding Pt catalyst and mass activity among the best of the Ru based catalysts under acidic conditions. The integration of proton exchange membrane water electrolysis with Ru/NPCS as a cathode exhibited an excellent hydrogen generation activity and extraordinary stability (during 120 h of electrolysis) with a 1/48 Ru loading (16.5 µgRu·cm−2) of a commercial 20% Pt/C catalyst. Through precisely tailoring the dispersion status of the catalysts, we reveal that while ruthenium nanoclusters actively catalyze HER via Volmer–Tafel mechanism, the Ru SACs barely catalyze HER, with H* adsorption difficult to occur. Moreover, no synergy between Ru SACs and Ru cluster is revealed, meaning the Ru SACs act as a spectator rather than active species during H2 evolution.

Research Article Issue
Tuning the oxidation state of Ru to surpass Pt in hydrogen evolution reaction
Nano Research 2021, 14 (11): 4321-4327
Published: 12 August 2021

The high price of state-of-the-art Pt electrocatalysts has plagued the acidic water electrolysis technique for decades. As a cheaper alternative to Pt, ruthenium is considered an inferior hydrogen evolution reaction (HER) catalyst than Pt due to its high susceptibility to oxidation and loss of activity. Herein, we reveal that the HER activity on Ru based catalysts could surpass Pt via tuning Ru oxidation state. Specifically, RuP clusters encapsulated in few layers of N, P-doped carbon (RuP@NPC) display a minimum over potential of 15.6 mV to deliver 10 mA·cm−2. Moreover, we for the first time show that a Ru based catalyst could afford current density up to 4 A·cm−2 in a practical water electrolysis cell, with voltage even lower than the Pt/C-based cell, as well as high robustness during 200 h operation. Using a combination of experiment probing and calculation, we postulate that the suitably charged Ru (~ +2.4) catalytic center is the origin for its superior catalytic behavior. While the moderately charged Ru is empowered with optimized H adsorption behavior, the carbon encapsulation layers protect RuP clusters from over oxidation, thereby conferring the catalyst with high robustness.

Research Article Issue
Nanocluster PtNiP supported on graphene as an efficient electrocatalyst for methanol oxidation reaction
Nano Research 2021, 14 (8): 2853-2860
Published: 23 January 2021

In this study, phosphorus doped graphene supported PtNiP nanocluster electrocatalyst (PtNiP/P-graphene) was successfully prepared via a simple hypophosphite-assisted co-reduction method. The improved anchoring force and increased anchoring sites of graphene support result from phosphorus doping as well as size-confined growth effect of NaH2PO2 leads to uniform dispersion of ultrafine PtNiP nanoclusters. Doped P also promotes the removal of CO-like intermediate by adjusting Pt electronic structure combining with alloyed Ni via electronic effects. As a result, the as-prepared PtNiP/P-graphene catalyst with more exposed active sites and optimized electronic structure of Pt alloy shows excellent electrocatalytic performances for methanol oxidation reaction (MOR) both in activity and durability in an acidic medium.

Research Article Issue
Accelerated oxygen reduction on Fe/N/C catalysts derived from precisely-designed ZIF precursors
Nano Research 2020, 13 (9): 2420-2426
Published: 16 June 2020

Fe/N/C material is the most competitive alternative to precious-metal catalysts for oxygen reduction. In view of the present consensus on active centers, further effort is directed at maximizing the density of single Fe atoms. Here, the imperfections in commonly used doping strategy of Fe for the synthesis of zeolitic imidazolateframework (ZIF)-derived Fe/N/C catalysts are revealed. More importantly, a strikingly improved catalyst is obtained by a 'second pyrolysis’ method and delivers a half-wave potential of 0.825 V (vs. RHE) in acidic media. The strong confinement effect of carbonaceous host accounts for the formation of dense single-atom sites and thus the high activity. Our findings will potentially facilitate future improvement of M/N/C catalysts.

total 5