config.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © 2016 Magento. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Store:etc/config.xsd">
    <default>
        <payment>
            <sample_gateway>
                <debug>1</debug>
                <active>0</active>
                <model>SamplePaymentGatewayFacade</model>
                <merchant_gateway_key backend_model="Magento\Config\Model\Config\Backend\Encrypted" />
                <order_status>pending_payment</order_status>
                <payment_action>authorize</payment_action>
                <title>Payment method (SampleGateway)</title>
                <currency>USD</currency>
                <can_authorize>1</can_authorize>
                <can_capture>1</can_capture>
                <can_void>1</can_void>
                <can_use_checkout>1</can_use_checkout>
                <is_gateway>1</is_gateway>
                <sort_order>1</sort_order>
                <debugReplaceKeys>MERCHANT_KEY</debugReplaceKeys>
                <paymentInfoKeys>FRAUD_MSG_LIST</paymentInfoKeys>
                <privateInfoKeys>FRAUD_MSG_LIST</privateInfoKeys>
            </sample_gateway>
        </payment>
    </default>
</config>