Serious interface carrier recombination leads to moderated photocatalytic performance of carbon nitride (C 3 N 4 ), and the realization of their strongly covalent bonding with co-catalysts can efficiently inhibit this. In this article, C 3 N 4 nanosheets are first functionalized with L-cysteine molecules to form C-SH bonds, and then the photodeposited CoP x NPs are covalently bonded with C 3 N 4 with L-cysteine molecules as bridging ligands, which can efficiently reduce the C 3 N 4 /CoP x interface impedance. Their optimal hydrogen evolution rate and apparent quantum efficiency at 420 nm are 4.12 mmolg −1 h −1 and 3.74%, respectively, which are 17.2 and 13.9 times that C 3 N 4 /CoP x reference without L-cysteine bridging ligands, mainly due to the reduced C 3 N 4 /CoP x interface impedance. This work proposes a general solution to inhibit interface carrier recombination in nanocomposites by introduction of bridging ligands.
Cobalt phosphides based materials are considered as promising electrocatalysts for the hydrogen evolution reaction (HER). The catalytic performance can be further enhanced by improving the intrinsic catalytic activity, exposing more active sites and coupling with conductive support. Herein, a novel electrocatalyst based on nitrogen doped reduced graphene oxides decorates with uniformly distributed CoP x nanoparticles with a suitable P/Co ratio ( x = 1.7) via a facile and mild condition. The optimized composite (CoP x /N-rGO) exhibits superior electrocatalytic HER activities with a low overpotential of 104 mV (at 10 mA cm −2 ), a small Tafel slope of 65 mV dec −1 , and long-term stability in the alkaline media, comparable to the performance of other HER electrocatalysts. The remarkable HER performance can be ascribed to the good electrical conductivity of rGO and extra active sites created by nitrogen doping. In addition, the ultrafine nanostructure (average particle size ≈4 nm) and well-dispersed CoP x nanoparticles also help expose more active sites for electrocatalytic reactions, largely hindering the agglomeration and exfoliation. This work provides a versatile route on the design of multifunctional composite materials for renewable energy research with low cost and high activity.
Design and synthesis of highly effective catalysts for electrochemical oxygen reduction reaction (ORR) with low cost is of great significance due to the purpose of energy conversion and storage. Herein, we report a facile solvothermal method to prepare ultrafine cobalt phosphide (CoPx)-doped Co-based zeolitic imidazole framework (CoPx/ZIF-67). The one-pot synthesis of CoPx/ZIF-67 involves an oxygen-free sealed room-temperature reaction, in which the high chemical activity of rich defect sits in 2D black phosphorus quantum dots (BPQDs) endows edge-selective coordination /reduction of Co ions. Carbonization of CoPx/ZIF-67 at 800 °C can produce CoPx-N-doped porous carbon composites (CoPx-NPC). The as-prepared CoPx-NPC retains the intrinsic morphology of rhombic dodecahedrons, similar to that of NPC derived from ZIF-67. The ultrafine CoPx doping causes chemical and electronic modulation and offers more active electrocatalytic sites etc., so that CoPx-NPC possesses enhanced ORR performance in terms of positive onset-potential (∼−0.06 V vs. SCE), large diffusion limiting current density (−4.703 mA cm −2 ), high stability, as well as the accelerated reaction kinetics.
X. Wu,S. Chen,Y. Feng,Q. Yuan,J. Gao,Y. Chen,Y. Huang,Y.-B. He,W. Gan
The development of bifunctional cathode catalysts with advantages such as high activity, low cost, and high durability is highly desirable and challenging for zinc-air batteries (ZABs) in energy applications . In this work, a novel type of bifunctional catalyst (CoP x /Co-N x -C@CNT) simultaneously effective for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) was prepared via a simplified all-in-one phosphorization-carbonization synthesis, which is distinctively different from the previously reported carbonization and postphosphorization route. With the integration of efficient catalytic factors such as Co-N x -C–coordinated moieties, cobalt phosphide, graphitic carbon shells, as well as a supportive and conductive matrix, the as-prepared CoP x /Co-N x -C@CNT exhibits high catalytic activity for ORR and OER in 0.1 M KOH, with an output positive onset potential of 0.92 V vs reversible hydrogen electrode (RHE) for ORR and a low potential of 1.69 V vs RHE at 10 mA cm −2 for OER. Remarkably, the assembled liquid and all-solid-state ZAB based on the as-prepared CoP x /Co-N x -C@CNT showed superior cycling performance than the results of its Pt/C-based counterparts and some recently reported cobalt phosphide–based ZABs. The good flexibility and reversibility of the all-solid-state ZAB also verified its feasibility in applications such as wearable electronics .
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