Structurally Ordered Intermetallic Cobalt Stannide Nanocrystals for High‐Performance Electrocatalytic Overall Water‐Splitting

Abstract

The synthesis of structurally ordered non‐noble intermetallic cobalt stannide (CoSn2) nanocrystals and their utilization for high‐performance electrocatalytic overall water‐splitting is presented. The structurally and electronically beneficial properties of the tetragonal CoSn2 exhibit a considerably low overpotential for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) on fluorine‐doped tin oxide (FTO) and Ni foam (NF). Loss of Sn from the crystal lattices and oxidation of Co under strongly alkaline conditions furnishes highly disordered amorphous active CoOx(H), the catalytically active structure for OER. The Co0 atoms in the CoSn2 act as active sites for HER and the presence of Sn provides efficient electrical conductivity. This intermetallic phase is a novel type of cost‐effective and competitive bifunctional electrocatalysts and predestinated for overall water‐splitting devices: A two‐electrode electrolyzer with CoSn2 on NF delivers a cell voltage of merely 1.55 V at 10 mA cm−2 maintaining long‐term stability.

Surface states in bulk single crystal of topological semimetal Co 3 Sn 2 S 2 toward water oxidation

“…When the thermodynamic OER potential (E 0 H2O/O2 = 1.23 V) is used as the reference, an overpotential of just 300 mV is required to reach a current density of 10 mA cm −2 . This value is close to, or even smaller than that for nanostructured electrocatalysts with a considerably larger surface area (Figure 2b), such as (Ni/Co)0.85Se nanotube arrays (255 mV), (24) CoN nanowires (290 mV), (25) CoSn2 nanocrystals (299 mV), (26) and NiCo metal-organic framework nanosheets (371 mV). (27)(28)(29) Crushing the bulk single crystal into small particles and deposited these onto Ni foam results in a further enhanced OER performance with an overpotential of 270 mV at 10 mA cm −2 .…”

N‐Doped Carbon Nanotubes Encapsulating Ni/MoN Heterostructures Grown on Carbon Cloth for Overall Water Splitting

“…The small Tafel slope for Ni/MoN@NCNT/CC shows that it has superior electrocatalytic activity because the rate of this catalyst in OER increases faster with the increasing potential. In addition, the faradaic efficiency (FE) of Ni/MoN@NCNT/CC for OER in 1.0 M KOH was measured through a drainage method, as shown in Figure S9 (The calculations in detail are shown in supporting information) . The high FE (97.4 %, Table S1) on Ni/MoN@NCNT/CC electrode suggests the high current density mainly contributes to oxygen evolution.…”

The Pivotal Role of s‐, p‐, and f‐Block Metals in Water Electrolysis: Status Quo and Perspectives

“…Among these lean metals, those referred to Al, Ga, Sn, and Bi are usually utilized for the OER and HER catalysis, and they improve the OER and HER activity in terms of the following aspects. [ 103,105,206–231 ] i) These lean metals can be readily etched in both the alkaline and acidic solutions, generating beneficial results including the formation of pores and partial phase reconstruction. ii) They can be prone to hybrid with other metals to form the (ordered) intermetallics with high conductivity.…”

“…Recently, Menezes et al demonstrated a controllable synthesis of CoSn 2 nanocrystals as efficient bifunctional OER and HER electrocatalysts using the solution chemistry method. [ 206 ] It was found that under alkaline media, the leaching of Sn from the crystal lattices, and oxidation of Co furnished highly disordered amorphous active CoO x (H) on the surface of CoSn 2 for OER, while the Co 0 atoms in the CoSn 2 acted as active sites for HER. Meanwhile, the retention of partial intermetallic CoSn 2 structure ensured high electrical conductivity to accelerate the charge transfer.…”

“…Moreover, to the best of our knowledge, considerable SPFM-mediated NNTM-based electrocatalysts exhibited a high capability to retain their original structure during the HER process. [105,206,218,267] This might be due to the partial electrons transfer toward NNTM from SPFM species, by increasing the charge density at the d-band orbitals of NNTM, and accordingly, preventing the severe (hydro)oxidation of TM, thereby optimizing their stability. [44,96] On the whole, although the operation stability of the NNTM-based electrocatalysts could be remarkably enhanced in the presence of SPFM species, the detailed analysis of the stabilizing mechanism is still currently unclear.…”