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Proton-exchange membrane fuel cells (PEMFCs) are limited by their extreme sensitivity to trace-level CO impurities, thus setting a strict requirement for H2 purity and excluding the possibility to directly use cheap crude hydrogen as fuel. Herein, we report a proof-of-concept study, in which a novel catalyst comprising both Ir particles and Ir single-atom sites (IrNP @IrSA -N-C) addresses the CO poisoning issue. The Ir single-atom sites are found not only to be good CO oxidizing sites, but also excel in scavenging the CO molecules adsorbed on Ir particles in close proximity, thereby enabling the Ir particles to reserve partial active sites towards H2 oxidation. The interplay between Ir nanoparticles and Ir single-atom centers confers the catalyst with both excellent H2 oxidation activity (1.19 W cm-2 ) and excellent CO electro-oxidation activity (85 mW cm-2 ) in PEMFCs; the catalyst also tolerates CO in H2 /CO mixture gas at a level that is two times better than that of the current best PtRu/C catalyst.

The applications of the most promising Fe-N-C catalysts are prohibited by their limited intrinsic activities. Manipulating the Fe energy level through anchoring electron-withdrawing ligands is found effective in boosting the catalytic performance. However, such regulation remains elusive as the ligands are only uncontrollably introduced oweing to their energetically unstable nature. Herein, we report a rational manipulation strategy for introducing axial bonded O to the Fe sites, attained through hexa-coordinating Fe with oxygen functional groups in the precursor. Moreover, the O modifier is stabilized by forming the Fe-O-Fe bridge bond, with the approximation of two FeN4 sites. The energy level modulation thus created confers the sites with an intrinsic activity that is over 10 times higher than that of the normal FeN4 site. Our finding opens a novel strategy to manage coordination environments at an atomic level for high activity ORR catalysts.

Single-atom catalysts (SACs) are attracting widespread interest for the catalytic oxygen reduction reaction (ORR), with Fe-Nx SACs exhibiting the most promising activity. However, Fe-based catalysts suffer serious stability issues as a result of oxidative corrosion through the Fenton reaction. Herein, using a metal-organic framework as an anchoring matrix, we for the first time obtained pyrolyzed Cr/N/C SACs for the ORR, where the atomically dispersed Cr is confirmed to have a Cr-N4 coordination structure. The Cr/N/C catalyst exhibits excellent ORR activity with an optimal half-wave potential of 0.773 V versus RHE. More excitingly, the Fenton reaction is substantially reduced and, thus, the final catalysts show superb stability. The innovative and robust active site for the ORR opens a new possibility to circumvent the stability issue of the non-noble metal ORR catalysts.

Single-atom FeN4 sites at the edges of carbon substrates are considered more active for oxygen electrocatalysis than those in plane; however, the conventional high-temperature pyrolysis process does not allow for precisely engineering the location of the active site down to atomic level. Enlightened by theoretical prediction, herein, a self-sacrificed templating approach is developed to obtain edge-enriched FeN4 sites integrated in the highly graphitic nanosheet architecture. The in situ formed Fe clusters are intentionally introduced to catalyze the growth of graphitic carbon, induce porous structure formation, and most importantly, facilitate the preferential anchoring of FeN4 to its close approximation. Due to these attributes, the as-resulted catalyst (denoted as Fe/N-G-SAC) demonstrates unprecedented catalytic activity and stability for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) by showing an impressive half-wave potential of 0.89 V for the ORR and a small overpotential of 370 mV at 10 mA cm-2 for the OER. Moreover, the Fe/N-G-SAC cathode displays encouraging performance in a rechargeable Zn-air battery prototype with a low charge-discharge voltage gap of 0.78 V and long-term cyclability for over 240 cycles, outperforming the noble metal benchmarks.

PtRu is regarded as the best catalyst for direct methanol fuel cells, but the performance decay resulting from the loss of Ru seriously hinders commercial applications. Herein, we demonstrated that the presence of Ni2 P largely reduces Ru loss, which thus makes the application of PtRu much stronger in direct methanol fuel cells. Outstanding catalytic activity and stability were observed by cyclic voltammetry. Upon integrating the catalyst material into a practical direct methanol fuel cell, the highest maximum power density was achieved on the PtRu-Ni2P/C catalyst among the reference catalysts at different temperatures. A maximum power density of 69.9 mW cm(-2) at 30 °C was obtained on PtRu-Ni2P/C, which is even higher than the power density of the state-of-the-art commercial PtRu catalyst at 70 °C (63.1 mW cm(-2)). Moreover, decay in the performance resulting from Ru loss was greatly reduced owing to the presence of Ni2 P, which is indicative of very promising applications.

Vanadium carbide incorporated on resorcinol-formaldehyde resin carbon (v8c7@rfc) was synthesized as a novel mesoporous catalyst-support material by pyrolysis of the resorcinol-formaldehyde resin and navo3 mixture. the material's bet surface area was 564 m(2)g(-1) and thus much higher than that of 389 m(2)g(-1) for the carbon powders yielded by resin carbonation. physical characterization revealed that the supporting material possesses a mesoporous structure and pt nanoparticles are homogeneously dispersed on the v8c7@rfc surface. electrochemical measurements demonstrated that the v8c7-modified pt catalyst exhibits a negative shift of over 100 mv in the onset potential for coads electrooxidation and a dramatically enhanced activity in methanol oxidation reaction. the enhancement was mainly attributed to the electronic effect between pt and v8c7 and the mesoporous structure providing ideal anchor sites for pt dispersion.

Ultrathin PtCux (x=1, 2 and 3) nanowire networks (NWMs) with controllable compositions were successfully synthesized by using Triton X-100 as the structure-directing agent in aqueous solution. The as-prepared PtCux nanocrystals were characterized by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammetry, and chronoamperometry. The results show that electrocatalytic performance of the PtCux NWNs towards the methanol oxidation reaction is enhanced relative to that of commercial Pt/C catalysts. Moreover, if the initial atomic ratio of Pt/Cu is 1:2, the corresponding PtCu2 NWNs catalyst generates mass activity that is 3.77-fold higher and specific activity that is 2.71-fold higher than the corresponding properties of commercial Pt/C catalysts. The enhanced activity can be attributed to a unique structure and a modified electronic effect.

The ptau alloy nanowire networks (nwns) were synthesized directly in an aqueous solution using triton x-114 as the structure-inducing agent. the nmns formed based on the oriented-attachment growth mechanism, and they exhibited dramatically enhanced electrocatalytic activity for formic acid electrooxidation compared with commercial pt black. besides the ensemble effect, the advantages of the unique structure, including superior electrical conductivity and faster electron-transfer for the electrochemical process, were regarded as the contributors to the superior catalytic activity of the as-prepared ptau nwns.

The direct formic acid fuel cell is an emerging energy conversion device for which palladium is considered as the state-of-the-art anode catalyst. In this communication, we show that the activity and stability of palladium for formic acid oxidation can be significantly enhanced using nickel phosphide (Ni(2)P) nanoparticles as a cocatalyst. X-ray photoelectron spectroscopy (XPS) reveals a strong electronic interaction between Ni(2)P and Pd. A direct formic acid fuel cell incorporating the best Pd–Ni(2)P anode catalyst exhibits a power density of 550 mWcm(-2), which is 3.5 times of that of an analogous device using a commercial Pd anode catalyst.

Microscale mass transfer structure in the anode catalyst layer (CL) can significantly alter the performance of a direct methanol fuel cell (DMFC) because it changes both the oxidation rate and crossover flux of methanol. The microscale mass transfer structure can be modified by changing the loading of the pore former (PF). An empirical model was developed for the microstructural design and optimization of anode CL by incorporating the PF into the anode CL. The optimal loading of PF is 100 g/m2 according to the calculated results. Experimental results confirmed the accuracy of the calculations, and the passive DMFC performs 37% better by incorporating the optimal loading of PF into the anode CL as compared to the conventional anode CL. The validity of the proposed empirical model can also be proven by comparing the calculated polarization results with the previously reported experimental data. © 2012 American Institute of Chemical Engineers AIChE J, 59: 780–786, 2013

The title catalyst is prepared by addition of NaBH4 solution to a mixture of HAuCl4, H2PdCl4, and ultrasonically dispersed carbon powder in H2O(25 °C, 8 h).