Sucrose leavening-induced hierarchically porous carbon enhanced the hydrogen evolution reaction performance of Pt nanoparticles

Guanine-Assisted Contrived Low Pt-Integrated Mo2C/C for Hydrogen Evolution Reaction

Due to the high cost of the available Pt electrocatalysts, the large-scale water electrolysis production of hydrogen has been hindered. Hydrogen generation via electrochemical water splitting is a renewable energy essential to a sustainable society, creating a distinct material interface that shows Pt-like properties with long-term stability crucial to hydrogen evolution reactions (HERs). Here, we synthesized the guanine-assisted facile synthesis of 1 wt % Pt/Mo2C/C having a layered type morphology via solid state calcined process followed by chemical reduction. The well-developed 1 wt % Pt/Mo2C/C heterostructure is analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES) to understand the percentage of Pt doped on Mo2C/C. The as-synthesized 1 wt % Pt/Mo2C/C heterostructure exhibits a better HER activity than a commercial Pt/C with a small overpotential of 19 mV to reach a current density at 10 mA cm-2 with a Tafel slope of 28 mV/dec. The catalyst 1 wt % Pt/Mo2C/C shows a long-term stability of 42 h in 0.5 M H2SO4. The layered sheet structure with the N-doped carbon (C) nanosheet, encapsulating well-dispersed Pt within the layers, significantly enhances the reaction kinetics of the 1 wt % Pt/Mo2C/C. This design creates a synergistic effect among Mo2C, Pt, and the carbon matrix, improving catalytic performance. Theoretical calculations using the density functional theory (DFT) indicate the active sites for hydrogen evolution on Pt-integrated Mo2C/C. The 1 wt % Pt/Mo2C/C possessed a significantly reduced ΔGH* value (-0.06 eV) as compared to the pristine Mo2C/C material (ΔGH* = 0.34 eV), suggesting a higher catalytic activity. This simple method offers a fresh means to make clearly defined carbides and sheds light on creating low-Pt catalysts for a scalable HER.

Mo2C promoted electrocatalysis of the Pt/Mo2C (C) heterostructure for a superior hydrogen evolution reaction

Constructing a unique electrochemical interface to enhance the catalytic capacity of Pt-based catalysts is indispensable for wider application of the hydrogen evolution reaction (HER). Herein, platinum-analogous molybdenum carbide (Mo₂C) was combined with a lower content of Pt to construct the Pt/Mo₂C (C) heterostructure via a solid-phase method, using ammonium molybdate as the precursor. Vulcan-C served as a support to promote the distribution of the Pt and Mo₂C heterostructure, and cooperative effects between Pt and the Mo₂C heterostructure contributed to the significantly improved catalytic capacity of Pt. The obtained Pt/Mo₂C (C) exhibits superior HER activity and enhanced long-term durability in the acidic medium, with a low overpotential of 38 mV at 10 mA cm^-2 and a low Tafel slope of 24 mV dec^-1. In particular, a drastically enhanced amount of H₂ production can be achieved (6837.28 mmol h^-1 g^-1). This facile approach not only provides a new pathway for constructing novel heterostructures but also gives an insight into the design of cost-effective Pt-based materials for an efficient HER.

Zinc- Fe/Fe5C2/Fe1-xS@Fe-N-C active sites grown on N-doped porous carbon toward efficient oxygen reduction reaction in zinc-air batteries

The development of efficient non-precious metal oxygen reduction reaction catalysts to replace Pt-based catalysts is of great significance to accelerate the commercial application of fuel cells. In this study, a hierarchical porous carbon oxygen reduction reaction catalyst with Fe/Fe₅C₂/Fe_1-xS@Fe-N-C active sites was developed via a simple and efficient solid-phase synthesis method. The introduction of zinc inhibited the growth and agglomeration of the nanoparticles and induced the formation of active nitrogen species and porosity, thus boosting the catalytic activity. The optimal FeZn-N-C-1 catalyst exhibited a high half-wave potential of 0.846 V, which is 24 mV higher than that of the commercial Pt/C, with a 4-e^- reaction path under alkaline conditions. When the FeZn-N-C-1 catalyst is employed as a cathode in a zinc-air battery, it achieves a high open circuit voltage of 1.54 V, power density of 143.6 mW cm^-2 and specific capacity of 804 mA h g^-1.

Interface-engineered Co3S4/CoMo2S4nanosheets as efficient bifunctional electrocatalysts for alkaline overall water splitting

Exploring bifunctional electrocatalysts with high efficiency, inexpensive, and easy integration is still the daunt challenge for the production of hydrogen on a large scale by means of water electrolysis. In this work, a novel free-standing Co₃S₄/CoMo₂S₄heterostructure on nickel foam by a facial hydrothermal method is demonstrated to be an effective bifunctional electrocatalyst for overall water splitting (OWS). The synthesized Co₃S₄/CoMo₂S₄electrocatalyst achieves ultralow overpotentials of 143 mV@10 mA cm^-2for hydrogen evolution reaction (HER) and 221 mV@25 mA cm^-2for oxygen evolution reaction (OER), respectively, in 1 M KOH. Moreover, it presents a greatly improved durability and stability under operando electrochemical conditions. When used as catalysts for OWS, the Co₃S₄/CoMo₂S₄-3//Co₃S₄/CoMo₂S₄-3 electrodes just need 1.514 V to make it to the current density of 10 mA cm^-2. It is supposed that the introduction of heterogeneous interface between Co₃S₄and CoMo₂S₄could give rise to plentiful active sites and enhanced conductivity, and thus boost excellent catalytic performances. Moreover, the porous feature of free-standing nanosheets on nickel foam could benefits catalytic performances by accelerating charge transport and releasing bubbles rapidly. This work proposes a bifunctional catalyst system with the heterogeneous interface, which could be used in a sustainable green energy system.

Recent Advances in Non-Precious Transition Metal/Nitrogen-doped Carbon for Oxygen Reduction Electrocatalysts in PEMFCs

The proton exchange membrane fuel cells (PEMFCs) have been considered as promising future energy conversion devices, and have attracted immense scientific attention due to their high efficiency and environmental friendliness. Nevertheless, the practical application of PEMFCs has been seriously restricted by high cost, low earth abundance and the poor poisoning tolerance of the precious Pt-based oxygen reduction reaction (ORR) catalysts. Noble-metal-free transition metal/nitrogen-doped carbon (M–NxC) catalysts have been proven as one of the most promising substitutes for precious metal catalysts, due to their low costs and high catalytic performance. In this review, we summarize the development of M–NxC catalysts, including the previous non-pyrolyzed and pyrolyzed transition metal macrocyclic compounds, and recent developed M–NxC catalysts, among which the Fe–NxC and Co–NxC catalysts have gained our special attention. The possible catalytic active sites of M–NxC catalysts towards the ORR are also analyzed here. This review aims to provide some guidelines towards the design and structural regulation of non-precious M–NxC catalysts via identifying real active sites, and thus, enhancing their ORR electrocatalytic performance.