Tweaking Nickel with Minimal Silver in a Heterogeneous Alloy of Decahedral Geometry to Deliver Platinum‐like Hydrogen Evolution Activity

Abstract

Five‐fold intertwined AgxNi1−x (x=0.01–0.25) heterogeneous alloy nanocrystal (NC) catalysts, prepared through unique reagent combinations, are presented. With only ca. 5 at % Ag (AgNi‐5), Pt‐like activity has been achieved at pH 14. To reach a current density of 10 mA cm−2 the extremely stable AgNi‐5 requires an overpotential of 24.0±1.2 mV as compared to 20.1±0.8 mV for 20 % Pt/C, both with equal catalyst loading of 1.32 mg cm−2. The turnover frequency (TOF) is as high as 2.1 H2 s−1 at 50 mV (vs. RHE). Site‐specific elemental analyses show the Ag:Ni compositional variation, where the apex and edges of the decahedra are Ag‐rich, thereby exposing Ni onto the faces to achieve maximum charge transport for an exceptional pH universal HER activity. DFT calculations elucidate the relative H‐atom adsorption capability of the Ni centers as a function of their proximity to Ag atom.

An earth-abundant bimetallic catalyst coated metallic nanowire grown electrode with platinum-like pH-universal hydrogen evolution activity at high current density

“…3e and f) and expectedly it is better or comparable to that of the best known catalysts reported to date (Tables S4 and S5 †). 5,[10][11][12][14][15][16][17][18][19][20][21][22][23][24][25][26][27][46][47][48] When coupled to NiFe-LDH, overall water splitting is obtained at 1.508 V by the NiFe-LDH (+) || Cu-m/Cu-W/NiCo-LDH (À) electrolyzer to achieve a current density of 10 mA cm À2 compared to IrO 2 (+) || 40 wt% Pt/C (À) which needs 1.55 V along with exceptional stability for almost 70 h at 333 mA cm À2 , making it suitable for practical applications (Fig. S20 †).…”

Oxygen‐Defect‐Rich Cobalt Ferrite Nanoparticles for Practical Water Electrolysis with High Activity and Durability

“…[1] At remendous amount of effort has been devoted to developing cleanersources of H 2 ,s uch as water electrolysis. [2] The process, however,i nvolves two half-reactions, the oxygen and hydrogen evolution reactions (OER and HER, respectively), and hence, there is a growingn eed for next-generation electrocatalysts to minimize any overpotential over the theoretical potential of 1.23 V. [2][3][4][5][6] To move away from expensive benchmark electrocatalysts, such as IrO 2 /RuO 2 /PtÀC-based catalysts, for the OER and HER, efforts are focusedo nd eveloping cheaper earth-abundant catalysts, mainly based on first-row transition metals,n amely,C o, Ni, Fe, and Mn, [7][8][9][10] including their oxides, phosphides,c halcogenides, and nitrides. [11][12][13] Major efforts are directed to inducingasuperior electrochemically active surface area (ECSA), high turnover frequency (TOF), and good pH universality to lower the overpotentials and catalyst mass loading.…”

Applications of Metal Nanocrystals with Twin Defects in Electrocatalysis

“…Twin defects are widely used in electrocatalysis due to their unique structure characters, and it has also been demonstrated that twin defects play an important role in modulating the HER activity of metal catalysts. [58][59][60] For example, Liu et al found that the twinned Pd 2 CoAg nano-crystals exhibited excellent HER performance in acidic media, in which the enhancement could attributed to the increased active sites caused by surface vacancies and twin boundaries. [58] In addition, Mu and co-workers obtained the five-twinned PtPdRuTe nanocrystal through solution-phase synthesis (Figure 9a-c), and found its higher electrocatalytic activities towards HER compared with the Pt/C in both alkaline and acidic media (Figure 9d, e).…”