As the NN bond in N is one of the strongest bonds in chemistry, the fixation of N to ammonia is a kinetically complex and energetically challenging reaction and, up to now, its synthesis is still heavily relying on energy and capital intensive Haber-Bosch process (150-350 atm, 350-550 °C), wherein the input of H and energy are largely derived from fossil fuels and thus result in large amount of CO emission. In this paper, it is demonstrated that by using Au sub-nanoclusters (≈0.5 nm ) embedded on TiO (Au loading is 1.542 wt%), the electrocatalytic N reduction reaction (NRR) is indeed possible at ambient condition. Unexpectedly, NRR with very high and stable production yield (NH : 21.4 µg h mg , Faradaic efficiency: 8.11%) and good selectivity is achieved at -0.2 V versus RHE, which is much higher than that of the best results for N fixation under ambient conditions, and even comparable to the yield and activation energy under high temperatures and/or pressures. As isolated precious metal active centers dispersed onto oxide supports provide a well-defined system, the special structure of atomic Au cluster would promote other important reactions besides NRR for water splitting, fuel cells, and other electrochemical devices.
Ammonia synthesis is one of the most kinetically complex and energetically challenging chemical processes in industry and has used the Harber-Bosch catalyst for over a century, which is processed under both harsh pressure (150-350 atm) and hightemperature (623-823 K), wherein the energy and capital intensive Harber-Bosch process has a huge energy cost accounting for about 1%-3% of human's energy consumption. Therefore, there has been a rough and vigorous exploration to find an environmentally benign alternative process. As the amorphous material is in a metastable state and has many "dangling bonds", it is more active than the crystallized one. In this paper, CeO -induced amorphization of Au nanoparticles anchored on reduced graphite oxide (a-Au/CeO -RGO) has been achieved by a facile coreduction method under ambient atmosphere. As a proof-of-concept experiment, a-Au/CeO -RGO hybrid catalyst containing the low noble metal (Au loading is 1.31 wt%) achieves a high Faradaic efficiency (10.10%) and ammonia yield (8.3 μg h mg ) at -0.2 V versus RHE, which is significantly higher than that of the crystalline counterpart (c-Au/RGO), and even comparable to the yields and efficiencies under harsh temperatures and/or pressures.
by mankind are invested and more than 300 million metric tons of CO 2 are generated annually. [4,5] Therefore, it is of imperative importance to reroute conventional N 2 fixation technologies and break the link between NH 3 producing and fossil fuels consuming. In response, N 2 fixation has triggered a worldwide "gold rush" and tremendous studies have been carried out recently. [6][7][8][9][10][11][12] As proposed approaches for N 2 fixation under milder conditions, using electricity to drive the NH 3 production reaction has become a good choice, [10] which represents a very attractive prospect for sustainable agriculture and achieves N 2 / NH 3 cycle to store and utilize energy from diffuse renewable sources. [13,14] Recently, some reports on electrochemical N 2 reduction reaction (NRR) with noble metal heterogeneous electrocatalysts have aroused interests in computational and experimental studies. [15][16][17] Although the suggested noble metal heterogeneous catalysts are optimally energetically efficient for NRR, their NRR catalytic activity cannot be fully demonstrated, because hydrogen evolution reaction (HER) dominates on these metals. [15][16][17] Additionally, the high costs and low abundance greatly restrict noble metal catalysts large-scale applications. To address these thorny problems, introducing transition metals with the noble ones to form polymetallic catalysts may reduce the amount of noble metal as well as improve the catalytic performance. [18][19][20] Actually, previous reports have demonstrated ternary materials can exhibit excellent performance for energy storage and conversion, such as oxygen reduction reaction, [21] oxygen evolution reaction, [22] sodium storage, [23] and so on. Therefore, the combination will be an effective means of extending the transition element properties and tuning the noble metal peculiarities. [24,25] To address this critical while daunting issue, as a proof-ofconcept experiment, taking Pd-Cu bimetallic alloys as examples, we propose and demonstrate that, by tuning the bimetallic mole ratios, NRR is indeed possible even at room temperature and atmospheric pressure. In order to enhance metallic utilization and prevent alloying nanoparticles (NPs) aggregation, 2D graphene sheets are also introduced for a good dispersion of alloys NPs. Herein, ultrafine Pd x Cu 1−x amorphous nanoclusters on reduced graphene oxide (rGO) were synthesized through a facile method. Taking prepared composites as electrochemical NRR catalysts, the optimal Pd 0.2 Cu 0.8 /rGO exhibits a yield of As an alternative approach for N 2 fixation under milder conditions, electrocatalytic nitrogen reduction reaction (NRR) represents a very attractive strategy for sustainable development and N 2 cycle to store and utilize energy from renewable sources. However, the research on NRR electrocatalysts still mainly focuses on noble metals, while, high costs and limited resources greatly restrict their large-scale applications. Herein, as a proof-of-concept experiment, taking PdCu amorphous nanocluster ancho...
Hematite (α-Fe 2 O 3 ) as a photoanode material for photoelectrochemical (PEC) water splitting suffers from the two problems of poor charge separation and slow water oxidation kinetics. The construction of p-n junction nanostructures by coupling of highly stable Co 3 O 4 in aqueous alkaline environment to Fe 2 O 3 nanorod arrays with delicate energy band positions may be a challenging strategy for efficient PEC water oxidation. It is demonstrated that the designed p-Co 3 O 4 /n-Fe 2 O 3 junction exhibits superior photocurrent density, fast water oxidation kinetics, and remarkable charge injection and bulk separation efficiency (η inj and η sep ), attributing to the high catalytic behavior of Co 3 O 4 for the oxygen evolution reaction as well as the induced interfacial electric field that facilitates separation and transportation of charge carriers. In addition, a cocatalyst of cobalt phosphate (Co-Pi) is introduced, which brings the PEC performance to a high level. The resultant Co-Pi/Co 3 O 4 /Ti:Fe 2 O 3 photoanode shows a photocurrent density of 2.7 mA cm −2 at 1.23 V RHE (V vs reversible hydrogen electrode), 125% higher than that of the Ti:Fe 2 O 3 photoanode. The optimized η inj and η sep of 91.6 and 23.0% at 1.23 V RHE are achieved on Co-Pi/Co 3 O 4 /Ti:Fe 2 O 3 , respectively, corresponding to the 70 and 43% improvements compared with those of Ti:Fe 2 O 3 . Furthermore, Co-Pi/Co 3 O 4 /Ti:Fe 2 O 3 shows a low onset potential of 0.64 V RHE and long-time PEC stability.
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