CoP Nanoframes as Bifunctional Electrocatalysts for Efficient Overall Water Splitting

Abstract

Transition-metal phosphides have been shown to be promising electrocatalysts in water for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). To maximize reactivity toward both entails limiting the catalyst size while maintaining reactivity and avoiding aggregation. Frame-like hollow nanostructures (nanoframes) provide the required open structure with sufficient channels into the interior volume. We demonstrate here the design and synthesis of CoP nanoframes (CoP NFs) by a strategy involving precipitation, chemical etching, and low-temperature phosphidation steps. It results in impressive bifunctional catalytic activities for both HER and OER and consequently enables a highly efficient water electrolyzer with a current density of 10 mA cm–2 driven by a cell voltage of only 1.65 V. The strategy has been generalized for the preparation of nanoframe Co dichalcogenides CoX2 NFs, with X = S, Se, and Te. The results of electrochemical measurements, supported by density functional theory calculations, show that HER catalytic activities for the series follow the sequence: CoP NFs > CoSe2 NFs > CoS2 NFs > CoTe2 NFs.

Ammonium Nitrate‐Assisted Low‐Temperature Synthesis of Co, Co2P@CoP Embedded in Biomass‐Derived Carbons as Efficient Electrocatalysts for Hydrogen and Oxygen Evolution Reaction

“…[4][5][6] The negatively charged P atoms in TMPs can not only capture protons as Lewis bases, but also effectively promote the desorption of H 2 from the active sites. Particularly, recent studies have shown that cobalt phosphides could act as bifunctional catalysts toward HER and OER, [7,8] through heteroatoms doping, [9,10] MOF coupling, [11,12] anodic electrochemical treating, [13] and hetero-structure engineering. [14] Preparation of cobalt phosphides generally involves two key procedures.…”

Hollow cobalt-nickel phosphide nanocages for efficient electrochemical overall water splitting

“…In particular, transition metal phosphides, especially bimetallic transition metal phosphides have attracted significant attentions as bi-functional electrocatalysts for water-splitting owing to their remarkably enhanced catalytic activities [32,33]. To maximize the electrochemical performance of the catalysts, endowing the electrocatalysts with hollow nanostructures is regarded as an effective approach, which can significantly increase their specific surface areas and expose more reactive sites [34][35][36][37]. Moreover, the ion diffusion length and transport resistance for water splitting can be effectively reduced by their large void spaces, which has been fully demonstrated by previous studies [38][39][40].…”

Coupling NiCo Alloy and CeO2 to Enhance Electrocatalytic Hydrogen Evolution in Alkaline Solution

“…The performance for the NiCo-CeO 2 ||NiCo(OH) x -CeO 2 electrolyzer also outperforms most recently reported electrolyzers based on non-noble bifunctional electrocatalysts (Figure 5e; Table S4, Supporting Information). [45][46][47][48][49][50][51][52][53][54][55][56][57][58][59] The excellent overall water splitting activity of the NiCo-CeO 2 ||NiCo(OH) x -CeO 2 electrolyzer is not only attributed to the high intrinsic catalytic activities of NiCo-CeO 2 / GP and NiCo(OH) x -CeO 2 /GP, but also to the self-supported electrode structure. Due to the in situ growth of active species on conductive substrate, the interface resistances of the self-supported NiCo-CeO 2 /GP and NiCo(OH) x -CeO 2 /GP electrodes are greatly lower than those of the Pt/C(20%)/GP and RuO 2 /GP electrodes by physically coating (Figure S25, Supporting Information), which are conducive to the rapid electron transfer.…”

“…The performance for the NiCo–CeO 2 ||NiCo(OH) x –CeO 2 electrolyzer also outperforms most recently reported electrolyzers based on non‐noble bifunctional electrocatalysts (Figure 5e; Table S4, Supporting Information). [ 45–59 ]…”