Shen Jia, Zhang Ping, Xie Ruishi, Chen Lin, Li Mengting, Li Jiapeng, Ji Bingqiang, Hu Zongyue, Li Jiajun, Song Lixian, Wu Yeping, Zhao Xiuli
State Key Laboratory of Environment-friendly Energy Materials , Southwest University of Science and Technology , Mianyang 621010 , P. R. China.
Institute of Chemical Materials , China Academy of Engineering Physics (CAEP) , Mianyang 621900 , P. R. China.
ACS Appl Mater Interfaces. 2019 Apr 10;11(14):13545-13556. doi: 10.1021/acsami.8b22260. Epub 2019 Apr 1.
Layered double hydroxides (LDHs), as an effective oxygen evolution reaction (OER) electrocatalyst, face many challenges in practical applications. The main obstacle is that bulk materials limit the exposure of active sites. At the same time, the poor conductivity of LDHs is also an important factor. Exfoliation is one of the most direct and effective strategies to increase the electrocatalytic properties of LDHs, leading to exposure of many active sites. However, developing an efficient exfoliation strategy to exfoliate LDHs into stable monolayer nanosheets is still challenging. Therefore, we report a new and efficient solid-phase exfoliation strategy to exfoliate NiFe LDH and graphene oxide (GO) into monolayer nanosheets and the exfoliating ratios of NiFe LDH and GO can reach up to 10 and 5 wt %, respectively. Based on the solid-phase exfoliation strategy, we accidentally discovered that there is a dynamic evolution process between NiFe-LDH nanosheets (NiFe-LDH-NS) and GO nanosheets (GO-NS) to assemble new NiFe-LDH/GO nanohybrids, i.e., NiFe-LDH-NS could be horizontal bespreading on GO-NS or well-organized standing on GO-NS, or both simultaneously. The electrocatalytic OER property test results show that NiFe-LDH/RGO-3 (NFRG-3) nanohybrids obtained by the reduction treatment of NiFe-LDH/GO-3 (NFGO-3) nanohybrids, in which NiFe-LDH-NS are well-organized standing on GO-NS, have excellent electrocatalytic properties for OER in an alkaline solution (with a small overpotential of 273 mV and a Tafel slope of 49 mV dec at the current density of 30 mA cm). The excellent electrocatalytic properties for OER of NFRG-3 nanohybrids could be attributed to the unique three-dimensional arraylike structure with many active sites. At the same time, reduced graphene oxide (RGO) with excellent conductivity can improve the charge-transfer efficiency and synergistically improve OER properties of nanohybrids.
层状双氢氧化物（LDHs）作为一种有效的析氧反应（OER）电催化剂，在实际应用中面临许多挑战。主要障碍是块状材料限制了活性位点的暴露。同时，LDHs的低导电性也是一个重要因素。剥离是提高LDHs电催化性能最直接有效的策略之一，可使许多活性位点暴露出来。然而，开发一种有效的剥离策略将LDHs剥离成稳定的单层纳米片仍然具有挑战性。因此，我们报道了一种新型高效的固相剥离策略，可将镍铁LDH和氧化石墨烯（GO）剥离成单层纳米片，镍铁LDH和GO的剥离率分别可达10 wt%和5 wt%。基于该固相剥离策略，我们意外发现镍铁-LDH纳米片（NiFe-LDH-NS）和GO纳米片（GO-NS）之间存在一个动态演化过程，以组装新的NiFe-LDH/GO纳米杂化物，即NiFe-LDH-NS可以水平铺展在GO-NS上，或有序地站立在GO-NS上，或两者同时存在。电催化OER性能测试结果表明，通过对NiFe-LDH/GO-3（NFGO-3）纳米杂化物进行还原处理得到的NiFe-LDH/RGO-3（NFRG-3）纳米杂化物，其中NiFe-LDH-NS有序地站立在GO-NS上，在碱性溶液中对OER具有优异的电催化性能（在电流密度为30 mA cm时，过电位小至273 mV，塔菲尔斜率为49 mV dec）。NFRG-3纳米杂化物对OER的优异电催化性能可归因于具有许多活性位点的独特三维阵列状结构。同时，具有优异导电性的还原氧化石墨烯（RGO）可以提高电荷转移效率，并协同改善纳米杂化物的OER性能。
