Colloidal Synthesis of Nickel Arsenide Nanocrystals for Electrochemical Water Splitting

Abstract

We report a detailed study on the first colloidal synthesis of NiAs nanocrystals. By optimizing the synthesis parameters, we were able to obtain trioctylphosphine-capped NiAs nanoplatelets with an average diameter of ∼10 nm and a thickness of ca. 4 nm. We then studied the performance of such NiAs nanocrystals as electrocatalysts for electrochemical water splitting reactions, namely, acidic hydrogen evolution reaction (HER) and alkaline oxygen evolution reaction (OER). These nanocrystals were found to be the most HER active ones among the transition metal arsenides reported to date despite exhibiting less than 40 h of stability under benchmark operative conditions (i.e., −10 mA cm geo −2 ). When tested as alkaline OER electrocatalysts, our NiAs nanocrystals behaved as a pre-catalyst and transformed superficially into an active Ni-oxy/hydroxide. As a result, NiAs nanocrystals featured an OER activity higher than that of benchmark Ni 0 nanocrystals. Noticeably, the OER performance, in terms of 10 mA cm OER geo 2 , was retained for up to 60 h of continuous operation. The present study highlights how transition metal arsenides, whose structural features could be successfully controlled through a proper tuning of the synthetic parameters, might represent an emerging class of materials for electrocatalytic applications.

Ease of Electrochemical Arsenate Dissolution from FeAsO4 Microparticles during Alkaline Oxygen Evolution Reaction

“…In such cases, the place exchange mechanism also plays an important role in the active monolayer formation . The newly formed high energy surface of FeO­(OH) with random atomic arrangement leads to facile electro-kinetics and better OER performance, as depicted from the Tafel analysis. ,,, Impedance analysis and R ct data indicated further that the formation of amorphous FeO­(OH) also helps in a better charge transfer.…”

“…65 The newly formed high energy surface of FeO(OH) with random atomic arrangement leads to facile electro-kinetics and better OER performance, as depicted from the Tafel analysis. 7,56,66,67 Impedance analysis and R ct data indicated further that the formation of amorphous FeO(OH) also helps in a better charge transfer. , where both the metals adopted octahedral geometry.…”

Controlling Phase in Colloidal Synthesis

“…Metal arsenides are limited in their studies, most of which are related to III–V quantum dots (QDs) or use noncolloidal syntheses such as ball milling . Some colloidal syntheses include work by the Jaramillo group who synthesized orthorhombic CoAs and MoAs crystals and hexagonal Cu 3 As crystals, and the Manna group who did the first colloidal NiAs synthesis . The Manna group also showed that control of the standard InAs synthesis could be added by mediating the reduction with ZnCl 2 , which improved the size distribution of the product, and allowed for a ZnSe shell .…”

“… 104 Some colloidal syntheses include work by the Jaramillo group who synthesized orthorhombic CoAs and MoAs crystals and hexagonal Cu 3 As crystals, 64 and the Manna group who did the first colloidal NiAs synthesis. 105 The Manna group also showed that control of the standard InAs synthesis could be added by mediating the reduction with ZnCl 2 , which improved the size distribution of the product, and allowed for a ZnSe shell. 106 While these studies show a diversity of metal arsenides the studies do not include any phase control.…”

Fe and Mo Co‐Modulated Coral‐like Nickel Pyrophosphate in situ Derived from Nickel‐Foam for Oxygen Evolution

“…However, their high cost and scarcity hinder their wide practical application and have stimulated the development of new low‐cost and durable non‐noble metal materials [8–10] . Among them, non‐noble transition metal‐based catalysts (TMBCs) with high abundance and diversity, inclusive of Ni, Mn, Co, V, Fe and Mo‐based compounds have been considered as promising alternatives in various forms, such as oxides, [11] (oxy)hydroxides, [12–14] phosphides, [15–17] borides, [18] carbides, [19] nitrides, [20] arsenides, [21,22] sulfides, [23–25] and selenides and tellurides [26] . Among all the transition metal‐based materials, nickel‐based electrocatalysts have attracted more attention due to their high abundance and low cost [27–39] …”