Active facet determination of layered double hydroxide for oxygen evolution reaction

Oxygen evolution reaction(OER) plays an indispensable role in developing renewable clean energy resources. One of the critical bottlenecks for the reaction is the development of highly efficient electrocatalyst to decrease the high overpotentials of four-electron transfer process of OER. Recently, layered double hydroxides(LDHs) have been widely investigated among the most promising electrocatalysts for OER due to their high intrinsic activity, excellent stability as well as low-cost. However, it remains unclear how the exposed facet of the LDHs affects their electrocatalytic activity. Here we elucidate the active edge facet of LDHs towards OER by combining the finely control of edge facet ratio coupled with molecular probe method and computational calculation. The LDHs with higher edge facet area ratio show superior activity with low onset potential as well as decreased Tafel slope. The active edge site is further proved by blocking the unsaturated edge sites with cyanate probe anion, of which the adsorption largely inhibits OER activity. Furthermore, based on density functional theory(DFT) calculation, twodimensional map of theoretical overpotentials as a function of Gibbs free energy reveals that the edge(100) facet exhibits a much higher OER activity than basal plane(001) facet.

A Method for Identifying Channeling Paths in Low-Permeability Fractured Reservoirs

Often oilfield fractured horizontal wells produce water flowing in multiple directions.In this study,a method to identify such channeling paths is developed.The dual-medium model is based on the principle of inter-well connectivity and considers the flow characteristics and related channeling terms.The Lorentz curve is drawn to qualitatively discern the geological type of the low-permeability fractured reservoir and determine the channeling direction and size.The practical application of such an approach to a sample oilfield shows that it can accurately identify the channeling paths of the considered low-permeability fractured reservoir and predict production performances according to the inter-well connectivity model.As a result,early detection of water channeling becomes possible,paving the way to real-time production system optimization in low-permeability fractured reservoirs.

双金属氢氧化物催化析氧反应的协同机制研究

双金属氢氧化物(LDH)是催化析氧反应(OER)活性最佳的一类催化剂,其中揭示双金属位点的协同作用是进一步提升其电催化、光催化性能的关键.本工作采用密度泛函方法,从理论计算角度探究了五种M3^(2+)N^(3+)-LDH (M^(2+)=Co^(2+)、Ni^(2+),N^(3+)=Al^(3+)、Cr^(3+)、Mn^(3+)、Fe^(3+))在催化OER中的反应机制和双金属位点的协同作用.研究结果表明,在电催化OER中,氧物种以桥连的方式同时吸附在双金属位点上,双位点协同作用降低了OER中的电势决定步骤的自由能变,并有效降低了电催化OER的过电位.Ni_(3)Fe-LDH在五种LDH中具有最高的电催化OER活性.在光催化OER中,双金属协同作用影响了LDH的带隙、功函数及驱动力,进而决定了LDH光催化OER的能力.所研究的五种LDH均为可见光响应,其中Ni_(3)Cr-LDH由于其驱动力大于过电位而被预测为良好的OER光催化剂.