Boosting Hydrogen Evolution Electrocatalysis via Regulating the Electronic Structure in a Crystalline–Amorphous CoP/CeO_x p–n Heterojunction

Abstract

The modulation of the electronic structure is the effective access to achieve highly active electrocatalysts for the hydrogen evolution reaction (HER). Transition-metal phosphide-based heterostructures are very promising in enhancing HER performance but the facile fabrication and an in-depth study of the catalytic mechanisms still remain a challenge. In this work, the catalytically inactive n-type CeO x is successfully combined with p-type CoP to form the CoP/CeO x heterojunction. The crystalline–amorphous CoP/CeO x heterojunction is fabricated by the phosphorization of predesigned Co­(OH)2/CeO x via the as-developed reduction–hydrolysis strategy. The p–n CoP/CeO x heterojunction with a strong built-in potential of 1.38 V enables the regulation of the electronic structure of active CoP within the space–charge region to enhance its intrinsic activity and facilitate the electron transfer. The functional CeO x entity and the negatively charged CoP can promote the water dissociation and optimize H adsorption, synergistically boosting the electrocatalytic HER output. As expected, the heterostructured CoP/CeO x -20:1 with the optimal ratio of Co/Ce shows significantly improved HER activity and favorable kinetics (overpotential of 118 mV at a current density of 10 mA cm–2 and Tafel slope of 77.26 mV dec–1). The present study may provide new insight into the integration of crystalline and amorphous entities into the p–n heterojunction as a highly efficient electrocatalyst for energy storage and conversion.

Construction of Frustrated Lewis Pair Sites in CeO2–C/BiVO4 for Photoelectrochemical Nitrate Reduction

“…In addition, CeO 2 has a strong redox performance, abundant surface oxygen defects, and structural firmness, showing excellent catalytic performance. Song et al constructed the CeO x heterostructure and demonstrated that CoP/CeO x could adjust the electronic structure to enhance the intrinsic activity and promote electron transfer, thus achieving high catalytic activity. , However, the collaborative controllability of chemisorption and catalytic activity is relatively limited in the traditional configuration of heterostructures because it is difficult to achieve the targeted design of surface sites. − In 2006, Stephan et al demonstrated that the small molecules could be efficiently reacted at the surface sites that were composed of sterically hindered Lewis acids (LAs) and Lewis bases (LBs), and these kinds of sites were known as “frustrated Lewis pairs (FLPs)” . LAs and LBs can accept and donate the electrons over small molecules, thereby realizing the chemical bond cleavage, which contributes to the optimization of catalysts. − For example, Huang’s group successfully established the stable FLPs by regulating the oxygen vacancies (O Vs ) of CeO 2 so as to promote the non-oxidative coupling of methane to high-value-added chemicals .…”

“…Song et al constructed the CeO x heterostructure and demonstrated that CoP/CeO x could adjust the electronic structure to enhance the intrinsic activity and promote electron transfer, thus achieving high catalytic activity. 18,19 However, the collaborative controllability of chemisorption and catalytic activity is relatively limited in the traditional configuration of heterostructures because it is difficult to achieve the targeted design of surface sites. 20−22 demonstrated that the small molecules could be efficiently reacted at the surface sites that were composed of sterically hindered Lewis acids (LAs) and Lewis bases (LBs), and these kinds of sites were known as "frustrated Lewis pairs (FLPs)".…”

Heterostructure Interface Engineering in CoP/FeP/CeOx with a Tailored d-Band Center for Promising Overall Water Splitting Electrocatalysis

“…The sheet-like CoP/CeO 2 heterostructure exhibits extraordinary OER performance originating from the interface-regulated oxygen vacancy and electronic interaction . In other heterophase materials, including NiFeLDH/CeO x , Cu 3 P/CeO 2 , and V-CoP/CeO 2 , CeO 2 can lower the needed energy for water dissociation and further promote the HER and even overall water splitting. − Our group has recently disclosed that the rod-inserting-cube CoP/CeO 2 and p–n CoP/CeO x heterojunctions exhibited higher HER activity than bare CoP due to the modulated electronic structure, especially for the d-band center. , Luo et al decorated CeO 2 on Co–Fe–P hollow hexagonal rods to enhance the HER activity by the optimization of the d-band center and hydrogen adsorption free energy . Nevertheless, the CeO 2 -induced metal phosphide interface with bifunctionality is rarely rare, yet of great interest with elaborate electronic structure modulation.…”

Anchoring Ce-modified Ni(OH)2nanoparticles on Ni-MOF nanosheets to enhances the oxygen evolution performance

“…15–18 Therein, heterostructures can increase the contact interface/surface and enhance charge transfer, leading to improved OER activities, 19 such as MnCo 2 O 4 /CeO 2 , 20 CeO 2 –CoS 1.97 , 21 and CoP/CeO x . 22…”

“…[15][16][17][18] Therein, heterostructures can increase the contact interface/surface and enhance charge transfer, leading to improved OER activities, 19 such as MnCo 2 O 4 /CeO 2 , 20 CeO 2 -CoS 1.97 , 21 and CoP/CeO x . 22 Because of the unique 4f electronic properties of cerium, Ce oxide possesses the potential to improve the OER performance by modulating the electronic structure and improving the charge transfer capability. [23][24][25] For example, Yan et al reported that Ce-doped Ni-Fe-Ce-LDH microcapsules show significantly improved performance with an overpotential of 242 mV at a current density of 10 mA cm −2 , which is attributed to electron transfer that is enhanced by the Ce-4f band modulation with d-f couplings.…”