Interfacial Engineering of Polycrystalline Pt₅P₂ Nanocrystals and Amorphous Nickel Phosphate Nanorods for Electrocatalytic Alkaline Hydrogen Evolution

Abstract

hydrogen evolution reaction (HER) owing to its optimal hydrogen adsorption energy and excellent stability. [5,6] However, its high cost and scarcity seriously limit its largescale commercialization. [7,8] Furthermore, its catalytic activity for alkaline HER is greatly decreased compared to that for acidic HER, which is primarily hindered by a sluggish water dissociation step in the alkaline electrolytes. [9][10][11][12] Therefore, a central challenge for Pt-based electrocatalysts is how to increase the intrinsic mass activity (MA) of Pt and lower the water dissociation energy barrier for the alkaline HER. [5,6,8,[13][14][15][16][17][18] To this end, intense research efforts focus on developing various approaches to improving the MA of Pt. [14][15][16][17][18][19] A common strategy is to alloy Pt with 3d transition metals (Fe, Co, Ni, W, etc.), or nonmetallic atoms (such as P, S, Se, and Te). For instance, the integration of Pt with P-forming platinum phosphide has proven effective in enhancing its catalytic activity, electron structure, and binding properties. [32][33][34] However, the bond between Pt atoms is extremely strong with a large bond energy of 306.7 kJ mol −1 resulting in the difficulty in breaking the Pt-Pt bond and introducing P into the Pt lattice to form platinum phosphide, [31] which normally requires either a high reaction temperature (>800 °C) or use of reactive and toxic organophosphorus precursors and dangerous white/red phosphorus. [35][36][37][38] Thus, the mild synthesis of platinum phosphide remains a Electrocatalytic hydrogen evolution reaction (HER) in alkaline media is important for hydrogen economy but suffers from sluggish reaction kinetics due to a large water dissociation energy barrier. Herein, Pt 5 P 2 nanocrystals anchoring on amorphous nickel phosphate nanorods as a high-performance interfacial electrocatalyst system (Pt 5 P 2 NCs/a-NiPi) for the alkaline HER are demonstrated. At the unique polycrystalline/amorphous interface with abundant defects, strong electronic interaction, and optimized intermediate adsorption strength, water dissociation is accelerated over abundant oxophilic Ni sites of amorphous NiPi, while hydride coupling is promoted on the adjacent electron-rich Pt sites of Pt 5 P 2 . Meanwhile, the ultra-small-sized Pt 5 P 2 nanocrystals and amorphous NiPi nanorods maximize the density of interfacial active sites for the Volmer-Tafel reaction. Pt 5 P 2 NCs/a-NiPi exhibits small overpotentials of merely 9 and 41 mV at −10 and −100 mA cm −2 in 1 M KOH, respectively. Notably, Pt 5 P 2 NCs/a-NiPi exhibits an unprecedentedly high mass activity (MA) of 14.9 mA µg Pt −1 at an overpotential of 70 mV, which is 80 times higher than that of Pt/C and represents the highest MA of reported Pt-based electrocatalysts for the alkaline HER. This work demonstrates a phosphorization and interfacing strategy for promoting Pt utilization and in-depth mechanistic insights for the alkaline HER.

Homogeneous Crystalline/Amorphous Interface in Ni(OH)2 Nanosheets for Enhanced Urea Oxidation Reaction

“…(iii) The lamellar structure exposes more accessible catalytically active surface sites and facilitates the mass transfer of reactants and gaseous products on the catalyst surface during electrochemical reactions. 29,20…”

Recent Progress of Amorphous Nanomaterials

“…(c) TEM image of CS-NS/NF; (d) HRTEM image of CS-NS/NF; and (e) EDS elemental mapping images Ni, V, O, and S in the CS-NS/NF electrode. (a) is adapted with permission from ref . Copyright 2022, Wiley-VCH GmbH.…”

“…210 Li et al developed a mild and facile one-step, two-phase method to construct a high-performance interfacial electrocatalyst system, involving Pt 5 P 2 nanocrystals anchored on Ni foam and amorphous Pt 5 P 2 (Pt 5 P 2 NCs/a-NiPi) nanorods for HER. 211 The schematic diagram is shown in Figure 31a. The top layer of the two-phase reaction mixture consists of oleylamine (OM) and octadecene (ODE).…”

Ultra‐Low Pt Doping and Pt–Ni Pair Sites in Amorphous/Crystalline Interfacial Electrocatalyst Enable Efficient Alkaline Hydrogen Evolution

“…[1,2] Electrochemical water splitting has proven to be a cost-effective, clean, and efficient energy conversion technology for hydrogen generation that has received a tremendous attention in the past decades. [3][4][5] Numerous studies have confirmed that noble metal catalysts (such as Pt and Ru) can catalyze the HER efficiently. [6][7][8] Nevertheless, their scarcity and high cost and the sluggish water dissociation process in alkaline electrolytes severely limit their application to HER, especially alkaline HER.…”

“…However, its excessively large ionic radius makes it difficult to achieve either interstitial doping or substitutional doping under mild conditions. Herein, a hierarchical nanostructured electrocatalyst with enriched amorphous/crystalline interfaces for high-efficiency alkaline HER is reported, which is composed of amorphous/crystalline (Co, Ni) 11 noble metals with earth-abundant transition metals compounds through doping [5,10,[24][25][26][27] and heterostructures [28][29][30] are effective ways to fundamentally reduce the load of noble metals. Among them, noble metal doping is considered as an effective way to maximize the MA of catalysts without sacrificing efficiencies and stability.…”