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.
Two-dimensional (2D) monoelemental antimonene has aroused great research interest since it emerged as a promising electrocatalyst for the hydrogen evolution reaction (HER). Nevertheless, the catalytic efficiency of the reported antimonene catalysts has been limited by their poor conductivity and lowdensity of exposed active sites. Herein, the active edge sites engineering is adopted to expose abundant catalytically active edge sites by decreasing the size of antimonene nanosheets to ultrasmall-sized antimonene nanodots (AMNDs). Meanwhile, the synergy effect of the surface modulation strategy by decorating the base surface of AMNDs using the ionic liquid benefits the mass transfer during the HER process. Impressively, the ionic liquid modified AMNDs (noted as IL-AMNDs) achieve a low overpotential of 116 mV at the current density of 10 mA cm À 2 and excellent long-term durability, even superior to many other previously reported 2D catalysts. This work spreads the way out for the development of highly active and efficient hydrogen production catalysts.
Constructing heterostructured electrocatalyst is a promising strategy to explore inexpensive and effective catalysts towards oxygen evolution reaction (OER), hydrogen evolution reaction (HER) and the overall water splitting (OWS). Here, amorphous NiO 2D layers decorated with Ni and rare earth oxide (REO x ) nanoparticles, which possess multiple heterostructures (NiÀ NiO and REO x -NiO), have been synthesized by the sequential electrodeposition on carbon cloth. The electrocatalytic performances for the prepared Er 2 O 3 /NiÀ NiO and CeO 2 /NiÀ NiO have been evaluated, exhibiting improved HER (39 mV@10 mA cm À 2 ) and OER (318 mV@50 mA cm À 2 ) activities in contrast to the single component, respectively. Additionally, the two-electrode system (Er 2 O 3 /NiÀ NiO//CeO 2 /NiÀ NiO) presents an excellent OWS property which displays a low potential of 1.58 V to reach 10 mA cm À 2 . This work helps to deepen the understanding of the synergetic interaction between dissimilar materials in heterostructured catalyst, and provides guidance for the further exploration and evolution of nanomaterials in green energy conversion technology.
Surface modulation and heteroatom doping are important approaches for boosting the electrocatalytic performances of MoS2 nanosheets. As a molecular electrocatalyst, the natural organic phytic acid (PA) offer attractive intermediate for oxygen evolution reaction (OER). Here, a surface modulation strategy is demonstrated through the decoration of PA onto the basal plane of iron (Fe)‐doped MoS2 nanosheets supported on nickel foam (NF) for boosted OER activity. Experimental results indicate that the PA modification and Fe doping could effectively boost the charge transfer and mass transport during the OER process. Specially, PA2‐Fe−MoS2 grown on NF (PA2‐Fe−MoS2/NF) exhibits excellent OER activity (218 mV@20 mA cm−2) and durability, even superior to RuO2 and many other previously reported OER catalysts. This natural organic molecule modification provides a facile strategy to designing low‐cost and efficient electrocatalytic materials.
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