Searching for highly efficient and cost‐effective electrocatalysts toward the hydrogen evolution reaction (HER) in alkaline electrolyte is highly desirable for the development of alkaline water splitting, but still remains a significant challenge. Herein, the rational design of Cr‐doped Co4N nanorod arrays grown on carbon cloth (Cr–Co4N/CC) that can efficiently catalyze the HER in alkaline media is reported. It displays outstanding performance, with the exceptionally small overpotential of 21 mV to obtain the current density of 10 mA cm−2 and good stability in 1.0 m KOH, which is even better than the commercial Pt/C electrocatalyst, and much lower than most of the reported transition metal nitride‐based and other non‐noble metal‐based electrocatalysts toward the alkaline HER. Density functional theory (DFT) calculations and experimental results reveal that the Cr atoms not only act as oxophilic sites for boosting water adsorption and dissociation, but also modulate the electronic structure of Co4N to endow optimized hydrogen binding abilities on Co atoms, thereby leading to accelerating both the alkaline Volmer and Heyrovsky reaction kinetics. In addition, this strategy can be extended to other metals (such as Mo, Mn, and Fe) doped Co4N electrocatalysts, thus may open up a new avenue for the rational design of highly efficient transition metal nitride‐based HER catalysts and beyond.

activities when compared to Pt/C is highly desirable, but still remains challenging.Transition metal phosphides (TMPs) have been investigated as a new class of effective HER catalysts due to their hydrogenase-like catalytic mechanism. [7] It has been reported that the introduction of phosphorus could modify the electronic structure of metal center, resulting in optimized reversible binding of hydrogen, which is considered as the key fact for boosting HER performance. [8] Despite intensive efforts have been made to develop pH-universal TMP-based electrocatalysts with both high-activity and long-term stability, only a few of them could exhibit comparable to, or even better activities than commercial Pt/C in acidic media. Adding insult to injury, Pt-free catalyst with superior catalytic performance to Pt/C under alkaline or/and neutral media has been rarely reported. Very recently, Li's group first reported the successful synthesis of Rh 2 P nanocubes with the average size of about 4.7 nm through a solvothermal method. [9] And the obtained Rh 2 P nanocubes exhibit good HER activities both in 0.5 m H 2 SO 4 and 0.1 m KOH. On the other hand, it is known that catalytic process occurs on the surface of catalysts, thus the size of catalysts is in connection with exposed active site numbers. [10] Experiment results show that nanocatalysts with decreased size often possess higher surface area and more active sites, resulting in enhanced catalytic activity. Consequently, developing ultrasmall TMPs with narrow size distribution may boost HER activity and even superior to the stateof-the-art Pt/C. Inspired by these ideas, in this work, we report the successful colloidal synthesis of monodisperse Rh 2 P nanoparticles (NPs) with an average size of 2.8 nm as well as their superior catalytic performances toward pH-universal HER. As expected, the monodisperse Rh 2 P NPs exhibit higher HER activities than Pt/C over a wide range of pH, with overpotentials of 14, 30, and 38 mV to achieve 10 mA cm −2 in 0.5 m H 2 SO 4 , 1.0 m KOH, and 1.0 m phosphate-buffered saline (PBS), respectively. As far as we know, this is the first example of Pt-free electrocatalyst possessing higher pH-universal HER performance than the state-of-the-art commercial Pt/C. Furthermore, density functional theory (DFT) calculations indicate that the H adsorption strength of Rh 2 P is weakened to nearly zero due to the introduction of P, thereby resulting in the outstanding HER performance.The search for Pt-free electrocatalysts exceeding pH-universal hydrogen evolution reaction (HER) activities when compared to the state-of-the-art commercial Pt/C is highly desirable for the development of renewable energy conversion systems but still remains a huge challenge. Here a colloidal synthesis of monodisperse Rh 2 P nanoparticles with an average size of 2.8 nm and their superior catalytic activities for pH-universal HER are reported. Significantly, the Rh 2 P catalyst displays remarkable HER performance with overpotentials of 14, 30, and 38 mV to achieve 10 mA cm −2 ...

Developing efficient electrocatalysts toward alkaline hydrogen oxidation and evolution reactions (HOR/HER) and fundamental understanding their catalytic mechanisms are highly desirable with the rapid development of hydrogen economy. Here, we report that the surface electronic structure of ruthenium (Ru) can be effectively modulated through phosphorus (P) doping to produce significantly enhanced catalytic HOR and HER performance in alkaline electrolyte. By controlling the amount of P, the resulted P–Ru/C exhibits outstanding catalytic activity, achieving a normalized exchange current density of 0.72 mA cm–2 and mass activity of 0.43 mA μg–1, approximately 5 and 3.5 times higher than those of Ru/C, respectively, and even 2 times higher than that of Pt/C (commercial 20 wt %) for HOR. Moreover, sixfold enhancement compared with Ru/C in the HER can be achieved from P–Ru/C. Experimental and density functional theory results indicate that electronic manipulation through P-doping is beneficial to the prominent HOR/HER performance and enhanced kinetics.

A series of heteroatom (S, N, and B) doped carbon supported Ni nanoparticles have been synthesized systematically and have shown remarkable performance toward the HOR in alkaline media.

Layered transition metal dichalcogenide (TMD) nanomaterials are promising alternatives to platinum (Pt) for the hydrogen evolution reaction (HER). However, the family of layered TMDs is mainly limited to Group IV-VII transition metals, while the synthesis of layered TMDs based on metals from other groups still remains a challenge. Herein, we demonstrate by atomic-resolution transmission electron microscopy that hexagonal RuSe 2 (h-RuSe 2) nanosheets with a mixture of 2H and 1T phases can be obtained by a facile bottom-up colloidal synthetic approach. The obtained h-RuSe 2 , which can be transformed into the thermodynamically favorable phase of cubic RuSe 2 (c-RuSe 2) only after annealing at 600 8C, exhibits Pt-like HER performance, with a fivefold turnover frequency enhancement compared to the c-RuSe 2 in alkaline media. Experimental results and density functional theory (DFT) calculations reveal that the enhanced adsorption free energies of H 2 O (DG H 2 O *), optimized adsorption free energies of H (DG H*), and increased conductivity of h-RuSe 2 contribute to its superior HER activity.

Conventional nanomaterials in electrochemical nonenzymatic sensing face huge challenge due to their complex size-, surface-, and composition-dependent catalytic properties and low active site density. In this work, we designed a single-atom Pt supported on Ni­(OH)2 nanoplates/nitrogen-doped graphene (Pt1/Ni­(OH)2/NG) as the first example for constructing a single-atom catalyst based electrochemical nonenzymatic glucose sensor. The resulting Pt1/Ni­(OH)2/NG exhibited a low anode peak potential of 0.48 V and high sensitivity of 220.75 μA mM–1 cm–2 toward glucose, which are 45 mV lower and 12 times higher than those of Ni­(OH)2, respectively. The catalyst also showed excellent selectivity for several important interferences, short response time of 4.6 s, and high stability over 4 weeks. Experimental and density functional theory (DFT) calculated results reveal that the improved performance of Pt1/Ni­(OH)2/NG could be attributed to stronger binding strength of glucose on single-atom Pt active centers and their surrounding Ni atoms, combined with fast electron transfer ability by the adding of the highly conductive NG. This research sheds light on the applications of SACs in the field of electrochemical nonenzymatic sensing.

Exploring efficient and economical electrocatalysts and understanding the mechanism for alkaline hydrogen oxidation reaction (HOR) are crucial to facilitate the development of alkaline polymer electrolyte fuel cells (APEFCs). Herein, Ru 2 P was synthesized and used as an anodic HOR electrocatalyst for APEFC, achieving a peak power density of 1.3 W cm −2 , the highest value among Pt-free anode electrocatalysts reported under the same conditions. From the density functional theory (DFT) calculations and experimental results, it was found that besides the optimized hydrogen binding energy, the enhanced adsorption strength of oxygenated species (OH*) and the reduced work function of Ru 2 P contributed to the enhanced HOR performance. The normalized exchange current densities of Ru 2 P/C were 0.37 mA cm ECSA −2 and 0.27 mA μg Ru −1, respectively, both approximately three times higher than those of Ru when conducted in the rotating disk electrode (RDE) system. Our work provides a new pathway for exploring highly active Pt-free HOR electrocatalysts and expanding the family of anodic electrocatalysts for APEFCs.

The kinetics of hydrogen oxidation reaction (HOR) under alkaline electrolyte, even for Pt, is orders of magnitude slower than that in acid; however, the origin that dominates the pH dependent HOR kinetics has not been unequivocally identified. Herein, Pd-Pd 4 S/C heterostructure is synthesized, and its HOR performance in the whole pH region is investigated. Unexpectedly, a non-monotonous variation between the current densities and pH is observed, whereas an inflection point occurring at a pH of around 7 is obtained. Moreover, the Pd-Pd 4 S/C heterostructure and its counterparts with almost identical hydrogen binding energies show HOR activity trends in accordance with their hydroxyl binding energies (OHBEs), highlighting the critical role of OHBE in enhancing HOR performance. The combination of experimental results and density functional theory calculations reveal that the electron transfer at the interface of Pd-Pd 4 S/C heterostructure promotes the OHBE and thereby accelerates the kinetics of alkaline HOR.